Air-Cooled Screw Compressor Chiller - Daikin Appliedlit.daikinapplied.com/bizlit/literature/lit_ch_ac/IMOM/...Operating Manual OM AGSD3 Group: Chiller Part Number: 331376101 Date:

Operating Manual OM AGSD3

Group: Chiller

Part Number: 331376101

Date: August 2007

Supercedes: New

Air-Cooled Screw Compressor Chiller

AGS 170D through AGS 210D

Software Version AGSG30101F

60 Hertz, R-134a

2 OM AGSD3

Table of Contents

Controller Features ...................................4 General Description...................................5

Control Panel Layout...............................5 Definitions ...............................................6

Component Description.............................9 Hardware Structure..................................9 System Architecture...............................10

Sequence of Operation ............................11 Controller Operation...............................17

Setpoints ................................................22 Controller Functions ...............................26

Parameter Definitions............................26 Unit Enable............................................26 Unit Mode Selection..............................28 Unit States .............................................29 Ice Mode Start Delay.............................30 Evaporator Pump Control......................30 Leaving Water Temperature (LWT) Reset

...............................................................31 Quiet Night Sound Reduction ...............33 Unit Capacity Overrides ........................33

BAS Interface...........................................34 Circuit Functions .....................................39

Calculations........................................... 39 Compressor Control .............................. 40 Condenser Fan Control ......................... 45 EXV Control ......................................... 47 Economizer Control .............................. 50

Alarms and Events .................................. 51 Unit Stop Alarms................................... 51 Unit Events............................................ 52 Circuit Stop Alarms............................... 52 Circuit Events........................................ 56 Alarm Logging...................................... 57 Event Logging....................................... 57

Using the Controller................................ 58 Security ................................................. 60 Editing Setpoints ................................... 61 Clearing Alarms .................................... 61 Unit Controller (CP1) Screens .............. 61 Editing Review...................................... 73

Start-up and Shutdown........................... 74 Temporary Shutdown............................ 74 Extended (Seasonal) Shutdown ............ 75

Field Wiring Diagram............................. 78

! DANGER

Dangers indicate a hazardous situation which will result in death or serious injury if not avoided.

! WARNING

Warnings indicate potentially hazardous situations, which can result in property damage, severe personal injury, or death if not avoided.

! CAUTION

Cautions indicate potentially hazardous situations, which can result in personal injury or equipment damage if not avoided.

2007 McQuay International. Information in this manual covers the McQuay International products at the time of publication and we reserve the right to make changes in design and construction at anytime without notice.

The following are trademarks or registered trademarks of their respective companies: BACnet from ASHRAE; LONMARK and LONWORKS Logo are managed, granted and used by LONMARK International uncer a license granted by Echelon Corporation; Modbus from Schneider Electric, Inc.;FanTrol,

Open Choices, McQuay and MicroTech II from McQuay International.

Manufactured in an ISO Certified facility

OM AGSD3 3

This manual provides setup, operating, and troubleshooting information for the McQuay

MicroTech ΙΙ controller for Model AGS-D3 vintage, air-cooled, rotary screw compressor

chillers. Please refer to the current version of the installation and maintenance manual IMM

AGSD3 (available on www.mcquay.com) for information relating to the unit itself.

Software Version: This manual covers units with Software Version AGSG30101F and

includes version E changes. The unit’s software version number can be viewed by pressing

the MENU and ENTER keys (the two right keys) simultaneously. Then, pressing the

MENU key will return to the Menu screen.

BOOT Version: 3.01F

BIOS Version: 3.62

! DANGER

Electric shock hazard: can cause personal injury or equipment damage. This equipment must be properly grounded. Connections to, and service of, the MicroTech II control panel must be performed only by personnel who are knowledgeable in the operation of the equipment being controlled

! WARNING

Static sensitive components. A static discharge while handling electronic circuit boards can cause damage to the components. Discharge any static electrical charge by touching the bare metal inside the control panel before performing any service work. Never unplug any cables, circuit board terminal blocks, or power plugs while power is applied to the panel.

NOTICE This equipment generates, uses and can radiate radio frequency energy and, if not installed and used in accordance with this instruction manual, can cause interference to radio communications. Operation of this equipment in a residential area can cause harmful interference, in which case the user will be required to correct the interference at the user’s own expense. McQuay International Corporation disclaims any liability resulting from any interference or for the correction thereof.

Temperature and Humidity Limitations

The MicroTech ΙΙ controller is designed to operate within an ambient temperature range of

-20°F to +149°F (-29°C to +65.1°C) with a maximum relative humidity of 95% (non-

condensing).

Language

This version of the software is set up for English language and inch-pounds units of measure

only.

4 OM AGSD3

Controller Features

• Readout of the following temperature and pressure readings:

• Entering and leaving chilled water temperature

• Saturated evaporator refrigerant temperature and pressure

• Saturated condenser temperature and pressure

• Outside air temperature

• Suction line, liquid line, and discharge line temperatures − calculated superheat for

discharge and suction lines

• Oil pressure

• Automatic control of primary and standby chilled water pumps. The control will start one

of the pumps (based on lowest run-hours) when the unit is enabled to run (not necessarily

running on a call for cooling) and when the water temperature reaches a point of freeze

possibility.

• Two levels of security protection against unauthorized changing of setpoints and other

control parameters.

• Warning and fault diagnostics to inform operators of warning and fault conditions in plain

language. All events and alarms are time and date-stamped for identification of when the

fault condition occurred. In addition, the operating conditions that existed just prior to an

alarm shutdown can be recalled to aid in isolating the cause of the problem.

• Twenty-five previous alarms and related operating conditions are available.

• Remote input signals for chilled water reset, demand limiting, and unit enable.

• Test mode allows the service technician to manually control the controllers’ outputs and

can be useful for system checkout.

• Building Automation System (BAS) communication capability via LONWORKS,

Modbus, or BACnet standard open protocols for all BAS manufacturers-simplified

with McQuay’s Open Choices feature.

• Pressure transducers for direct reading of system pressures. Preemptive control of low

evaporator pressure conditions and high discharge temperature and pressure to take

corrective action prior to a fault trip.

OM AGSD3 5

General Description

Control Panel Layout The control panel is located on the front of the unit, to the left of the power panel.

Table 1, Control Panel Components

Expansion Valve

Drivers Circuit Breakers

MicroTech II

Controller, CP1

MicroTech II Controller,

CP2,

On Three-Compressor

Units Only

Switches & Fuses

Terminal Blocks

6 OM AGSD3

Definitions

Active Setpoint The active setpoint is the setting in effect at any given moment. This variation occurs on

setpoints that can be altered during normal operation. Resetting the chilled water leaving

temperature setpoint by one of several methods, such as return water temperature, is an

example.

Active Capacity Limit The active setpoint is the setting in effect at any given moment. Any one of several external

inputs can limit a compressor’s capacity below its maximum value.

Condenser Saturated Temperature Target The saturated condenser temperature target is calculated by first using the following

equation:

Sat condenser temp target raw = 0.833(evaporator sat temp) + 68.34

The “raw” value is the initial calculated value. This value is then limited to a range defined

by the Condenser Saturated Temperature Target minimum and maximum setpoints. These

setpoints simply cut off the value to a working range, and this range can be limited to a

single value if the two setpoints are set to the same value.

Dead Band The dead band is a range of values surrounding a setpoint such that a change in the variable

occurring within the dead band range causes no action from the controller. For example, if a

temperature setpoint is 44°F and it has a dead band of ± 2 degrees F, nothing will happen

until the measured temperature is less than 42°F or more than 46°F.

DIN Digital input, usually followed by a number designating the number of the input.

Discharge Superheat Discharge superheat is calculated for each circuit using the following equation:

Discharge Superheat = Discharge Temperature – Condenser Saturated Temperature

Error In the context of this manual, “Error” is the difference between the actual value of a variable

and the target setting or setpoint.

Evaporator Approach The evaporator approach is calculated for each circuit. The equation is as follows:

Evaporator Approach = LWT – Evaporator Saturated Temperature

See page 38 for more details

Evap Recirc Timer A timing function, with a 30-second default, that holds off any reading of chilled water for

the duration of the timing setting. This delay allows the chilled water sensors (especially

water temperatures) to take a more accurate reading of the chilled water system conditions.

EXV Electronic expansion valve, used to control the flow of refrigerant to the evaporator,

controlled by the circuit microprocessor.

OM AGSD3 7

High Saturated Condenser – Hold Value High Cond Hold Value = Max Saturated Condenser Value – 5 degrees F

This function prevents the compressor from loading whenever the pressure approaches

within 5 degrees of the maximum discharge pressure. The purpose is to keep the

compressor online during periods of possibly temporary elevated pressures.

High Saturated Condenser – Unload Value High Cond Unload Value = Max Saturated Condenser Value – 3 degrees F

This function unloads the compressor whenever the pressure approaches within 3 degrees of

the maximum discharge pressure. The purpose is to keep the compressor online during

periods of possibly temporary elevated pressures.

Light Load Stg Dn Point The percent load point at which one of two operating compressors will shut off, transferring

the unit load to the remaining compressor.

Load Limit An external signal from the keypad, the BAS or a 4-20 ma signal that limits the compressor

loading to a designated percent of full load. Frequently used to limit unit power input.

Load Balance Load balance is a technique that equally distributes the total unit load among the running

compressors on a unit or group of units.

Low Ambient Lockout Prevents the unit from operating (or starting) at ambient temperatures below the setpoint.

Low Pressure Unload Setpoint The psi evaporator pressure setting at which the controller will unload the compressor until

a preset pressure is reached.

Low Pressure Hold Setpoint The psi evaporator pressure setting at which the controller will not allow further compressor

loading.

Low/High Superheat Error The difference between actual evaporator superheat and the superheat target.

LWT Leaving water temperature. The “water” is any fluid used in the chiller circuit.

LWT Error Error in the controller context is the difference between the value of a variable and the

setpoint. For example, if the LWT setpoint is 44°F and the actual temperature of the water

at a given moment is 46°F, the LWT error is +2 degrees.

LWT Slope The LWT slope is an indication of the trend of the water temperature. It is calculated by

taking readings of the temperature every few seconds and subtracting them from the

previous value, over a rolling one minute interval.

ms Milli-second

Maximum Saturated Condenser Temperature The maximum saturated condenser temperature allowed is calculated based on the

compressor operational envelope.

8 OM AGSD3

OAT Outside ambient air temperature

Offset Offset is the difference between the actual value of a variable (such as temperature or

pressure) and the reading shown on the microprocessor as a result of the sensor signal.

pLAN Peco Local Area Network is the proprietary name of the network connecting the control

elements.

Refrigerant Saturated Temperature Refrigerant saturated temperature is calculated from the pressure sensor readings for each

circuit. The pressure is fitted to an R-134a temperature/pressure curve to determine the

saturated temperature.

Soft Load

Soft Loading is a configurable function used to ramp up the unit capacity over a given time

period, usually used to influence building electrical demand by gradually loading the unit.

SP Setpoint

SSS Solid state starter as used on McQuay screw compressors.

Suction Superheat Suction superheat is calculated for each circuit using the following equation:

Suction Superheat = Suction Temperature – Evaporator Saturated Temperature

See page 38 for details.

Stage Up/Down Accumulator The accumulator can be thought of as a bank storing occurrences that indicate the need for

an additional fan.

Stageup/Stagedown Delta-T Staging is the act of starting or stopping a compressor or fan when another is still operating.

Startup and Stop is the act of starting the first compressor or fan and stopping the last

compressor or fan. The Delta-T is the “dead band” on either side of the setpoint in which no

action is taken.

Stage Up Delay The time delay from the start of the first compressor to the start of the second.

Startup Delta-T Number of degrees above the LWT setpoint required to start the first compressor.

Stop Delta-T Number of degrees below the LWT setpoint required for the last compressor to stop.

VDC Volts, Direct current, sometimes noted as vdc.

OM AGSD3 9

Component Description

Hardware Structure The controllers are fitted with a 16-bit microprocessor for running the control program.

There are controller terminals for connection to the controlled devices (for example:

solenoid valves, expansion valves, chilled water pumps). The program and settings are

saved permanently in FLASH memory, preventing data loss in the event of power failure

without requiring a back-up battery. The controllers also have optional remote

communication access capability for a BAS interface using standard protocols.

The Advanced MicroTech II controllers used on AGS-D chillers are not interchangeable

with previous MicroTech II controllers.

Keypad A 4-line by 20-character liquid crystal display and 6-button keypad are mounted on the unit

and compressor controllers.

Table 2, Keypad

Air Conditioning

ALARMVIEW

SET

<<<

Advanced

The four arrow keys (UP, DOWN, LEFT, RIGHT) have three modes of use.

1. Scroll between data screens in the direction indicated by the arrows (default mode).

2. Select a specific data screen in the menu matrix using dynamic labels on the right side

of the display such as ALARM, VIEW, etc. (pressing the MENU key enters this mode).

For ease of use, a visual pathway connects the appropriate button to its respective label

on the screen.

3. Change field values in setpoint programming mode as follows:

LEFT key = Default (D) RIGHT key = Cancel (C)

UP key = Increase (+) DOWN key = Decrease (-)

These four programming functions are indicated by a one-character abbreviation ( ) on the

right side of the display. This programming mode is entered by pressing the ENTER key.

vary an electric motor’s speed.

See the “Using the Controller” section beginning on page 58 for detailed instruction on

controller operation.

MENU Key Left Arrow w/ Red Alarm Light Behind

ARROW Keys (4) ENTER Key

10 OM AGSD3

System Architecture

• One large controller (CP1) is used on 2 circuit chillers (AGS 225 through 300) and a

second large controllers (CP2) is added on 3 circuit chillers (AGS 330 through 450).

• Expansion I/O boards are used and communicate via a tLan (J23). Two are used on 2

circuit chillers and four are used on 3 circuit chillers. Expansion I/O board #3 is used

when additional pump or circuit status enable options are ordered.

A block diagram is shown below

Table 3, System Block Diagram

NOTE: RAI=Remote Access Interface, EXB=Expansion Board

Table 4, pLAN Addressing

A pLAN is used to connect CP1 and CP2.

Controller Address Dip Sw 1 Position Dip Sw 2 Position Dip Sw 3 Position

Large 1 (CP1) 1 Up Down Down

Large 2 (CP2) 2 Down Up Down

Table 5, tLAN Addressing

A tLAN is used to connect the expansion modules to CP1 and CP2

Controller Expansion Serial Address

Large 1 PCOe1 1

Large 1 PCOe3 3

Large 1 PCOe4 4

Large 2 PCOe5 1

Large 2 PCOe8 4

BAS

Interface-

Bacnet,

Modbus,

Large

Controller CP1

4X20LCD

Large

Controller CP2

( 4X20LCD

RS485

/Lon

Expansion

I/O (EXB5)

Expansion

I/O (EXB8)

RS485

Expansion

I/O (EXB4)

Expansion

I/O (EXB3)

RS485

pLAN

Expansion

I/O (EXB1)

RAI Service

Tool(option)

OM AGSD3 11

Sequence of Operation

Table 6, Unit Sequence of Operation (see Table 6 for circuit sequence of operation)

Is unit enabled?

Is flow present?

Evaporator pump output on

Wait for chilled water loop torecirculate.

Is there enough load tostart chiller?

Start first circuit.

Yes

Yes

Yes

No

No

Unit power up

Unit in Off state

No

The chiller may be disabled via the unit switch, the remote switch, the keypadenable setting, or the BAS network. In addition, the chiller will be disabled if both

circuits are disabled, either because of an alarm or the circuit pumpdown switch on

each circuit, or if there is a unit alarm. If the chiller is disabled, the unit status

display will reflect this and also show why it is disabled.

If the unit switch is off, the unit status will be Off:Unit Switch. If the chiller is

disabled due to network command, the unit status will be Off:BAS Disable. When

the remote switch is open, the unit status will be Off:Remote Switch. When a unitalarm is active, the unit status will be Off:Unit Alarm. In cases where no circuits

are enabled, the unit status will be Off:All Cir Disabled.

If the chiller is enabled, then the unit will be in the Auto state and the evaporator

water pump output will be activated.

After establishing flow, the chiller will wait some time to allow the chilled water loopto recirculate for an accurate reading of the leaving water temperature. The unit

status during this time is Auto:Evap Recirc.

The chiller will then wait for the flow switch to close, during which time the unitstatus will be Auto:Wait for flow.

Keep pump output on whileunit is enabled.

The chiller is now ready to start if enough load is present. If the LWT is not high

enough to start, the unit status will be Auto:Wait for load.

If the LWT is high enough to start, the unit status will be Auto. A compressor can

start at this time.

The first circuit to start is generally the available circuit with the least number of

starts, or the lowest numbered circuit if there is a tie. This circuit will go through its

start sequence at this point.

12 OM AGSD3

Is more capacityneeded to satisfy load?

Has the stage up timedelay expired?

Start next circuit.

Yes

No

Load/unload as needed tosatisfy load.

Yes

No


Can less circuits handlethe load?

Yes

Shut down one circuit.

No


Is load satisfied?

No

Shut down last circuit.

Yes

The first circuit will load and unload as needed in an attempt to satisfy the load. It

will eventually get to a point where it is considered to be at full load. A circuit is at

full load when it reaches 75% slide target, it reaches the max slide target setting, or

it encounters a problem and is running in an inhibited state.

A minimum time must pass between the starting of circuits.

As the load drops off, the circuits will unload accordingly. If the LWT gets low

enough, or all running circuits unload enough, one circuit can shut off. This can

occur with either two or three circuits running.

When only one circuit is running, the load may drop off to the point where even

minimum unit capacity is too much. The load has been satisfied when the LWT

drops below the shutdown point. At this time the only running circuit can shut down.

All running circuits will now load/unload as needed to satisfy the load. In addition,

they will load balance so that both circuits are providing nearly equal capacity.

The second circuit will go through its start sequence at this point.

Note that a third circuit can be started if available. The two preceding conditions

must again be satisfied after starting the second circuit before starting the third

circuit.

The next circuit to shut off is generally the one with the most run hours.

The remaining running circuit(s) will load/unload as needed to satisfy the load.

The last circuit running now shuts down.

The unit should be ready to start again when the LWT gets high enough. The unit

status at this time will be Auto:Wait for load.

If a single circuit is not enough to satisfy the load, additional circuits will need to be

started.

OM AGSD3 13

Table 7, Circuit Sequence of Operation

Next on?

Next off?

Start Compressor

Stage down now?

Pumpdown circuit

Yes

Yes

Yes

No

No

Unit power up

Circuit is in Off state

No

When in the Run state, the compressor will load/unload as needed to satisfy theload. The compressor will also load/unload to load balance with other compressors

that are running and not in a limited condition. However, it cannot load up until thedischarge superheat has been over 22 F for at least 30 seconds. After this, the

circuit status will be Run:Normal.

The EXV will operate in either Pressure Control or Superheat Control. In Pressure

Control, the evaporator pressure is controlled to a target pressure, which is adjustedbased on LWT and discharge superheat. In Superheat Control, the suction

superheat is controlled to a target that varies with discharge superheat.

Fans will be staged on and off, and if available the VFD speed will be modulated, to

control the condenser pressure. The condenser pressure is controlled to a targetthat is based on evaporator pressure, with the target getting higher as the

evaporator pressure gets higher.

Stage up now?

Yes

No

Run Compressor

When the compressor starts, the EXV will open and begin controlling the evaporator

pressure. Depending on the OAT, a number of fans may be started with thecompressor to keep condenser pressure from climbing too fast. The circuit status

will normally be Run: Disc SH Low immediately after the compressor starts.

This compressor will be next on if it has the least starts of the compressors that are

not running and are available to run.

If there is a need for more cooling capacity, the compressor designated as next on

can start.

If this compressor has the most run hours of the running compressors, then thiscompressor will be designated as the next one off.

If less cooling capacity is needed, the compressor designated as next off can shut

down. This condition may arise when either the LWT has dropped far enough below

the active set point or all circuits are running at a low capacity.

When the circuit does a normal shutdown, a pumpdown is performed. The EXV isclosed while the compressor continues to run. As soon as the pumpdown is

initiated, the compressor is unloaded to the minimum. The condenser fans

continue to control normally during this process. The circuit status during this timeis Run:Pumpdown.

After the evaporator pressure drops below the pumpdown pressure or enough time

has passed, the compressor and fans are shut off to end the pumpdown process.

The circuit status will normally be Off:Cycle Timers at this time.

When the circuit is in the Off state the EXV is closed, compressor is off, and all fans

are off.

If the compressor is ready to start when needed, the circuit status will be

Off:Ready. When the circuit switch is off, the circuit cannot start and the status willbe Off:Pumpdown Switch.

14 OM AGSD3

Off Conditions Power is supplied to the power section of the electric panel. The standard power connection

is two separate sources, one to each circuit. Optionally, the power may be supplied to a

single power connection, either a power block or optional disconnect switch.

With power supplied to the unit, 115 VAC power is applied through the control fuse F1 to

the compressor heaters, HTR1 and HTR2, evaporator heater, and the primary of the 24V

control circuit transformer.

! CAUTION

Compressor heaters must be on for at least 12 hours prior to unit start-up to avoid compressor damage.

The 24V transformer provides power to the MicroTech II controller and related components.

With 24V power applied, the controller will check the position of the front panel system

switch Q0. If the switch is in the "stop" position, the chiller will remain off, and the display

will indicate the operating mode to be OFF: Unit Switch. The controller will then check

the pumpdown switches. If any of the switches are in the "stop" position, that circuit’s

operating mode will be displayed as OFF: Pump Down Switch. If the switches for both

circuits are in the "Stop" position, the unit status will display OFF: All Circuits Disabled.

If the remote start/stop switch is open the chiller will be OFF: Remote Switch. The chiller

may also be commanded off via communications from a separate communicating panel such

as a BAS protocol interface. The display will show OFF: BAS Disable if this operating

mode is in effect.

If an alarm condition exists which prevents normal operation of both refrigerant circuits, the

chiller will be disabled and the display will indicate OFF: Unit Alarm. If the control mode

on the keypad is set to "Manual Unit Off," the chiller will be disabled and the unit status

will display OFF: Keypad Disable.

Alarm The red alarm light in back of the left arrow key on the controller will be illuminated when

one or more of the cooling circuits has an active alarm condition which results in the circuit

being locked out or a unit alarm is active and manual reset is required. If only a circuit

alarm is active, the remaining circuits will operate as required. Events (low-level

occurrences) will not cause the key to light.

Start-up If none of the above "off" conditions are true, the MicroTech II controller will initiate a start

sequence and energize the chilled water pump output relay. The chiller will remain in the

WaitForFlow mode until the field-installed flow switch indicates the presence of chilled

water flow. Once flow is established, the controller will sample the chilled water

temperature and compare it against the Leaving Chilled Water Setpoint, the Control Band,

and the Start-up Delta-Temperature, which have been programmed into the controller’s

memory.

If the leaving chilled water temperature is above the Active Chilled Water Setpoint plus the

adjustable Start-up Delta-T, the controller will select the refrigerant circuit with the lowest

number of starts as the lead circuit and initiate a start request. The circuit controller will

open the EXV and start the compressor. A green light under the Enter key on the circuit

controller will illuminate to indicate that the compressor is running.

OM AGSD3 15

If additional cooling capacity is required, the controller will activate additional cooling. As

the system load increases, the controller will start the lag refrigerant circuit when the lead

circuit reaches 75%, or some other capacity limit is reached, and the interstage timers are

satisfied. The compressors and capacity control solenoids will automatically be controlled

as required to meet the cooling needs of the system.

The electronic expansion valves are operated by the MicroTech II controller to maintain

precise refrigerant control to the evaporator at all conditions.

Standard FanTrol Condenser Fan Control

When the compressor starts, a number of fans may be started, depending on the OAT and

the Forced Fan setpoints. The MicroTech II controller will activate the remaining condenser

fans as needed to maintain proper condenser pressure. The MicroTech II controller

continuously monitors the condenser pressure and will adjust the number of operating

condenser fans as required. The number of condenser fans operating will vary with outdoor

temperature and system load. The condenser fans are matched to the operating compressors

so that when a compressor is off, all fans for that circuit will also be off.

Pumpdown

As the system chilled water load requirements diminish, the compressors will unload. As

the system load continues to drop, the electronic expansion valve will be stepped closed, the

solenoid valve will close, and the refrigerant circuits will go through a pumpdown sequence.

As the evaporator pressure falls below the pumpdown pressure setpoint while pumping

down, the compressor and condenser fans will stop. The unit has a one-time pumpdown

control logic; therefore, if the evaporator pressure rises while the compressor is in the off

state, the controller will not initiate another pumpdown sequence. The circuit controller will

keep the compressor off until the next call for cooling occurs.

The chilled water pump output relay will generally remain energized until the unit is in the

Off State due to the remote stop switch, unit Off switch, BAS command, or keypad setting

calling for the unit to be disabled.

Liquid Line Solenoid Valve (LLSV)

The LLSV cycles with the compressor starter. Its purpose is to provide a positive seal in the

liquid line in the event of a power failure. A power failure may prevent the expansion valve

from closing completely by removing power before the valve steps all the way closed.

16 OM AGSD3

Table 8, AGSD3 Piping Schematic

CHARGING

VALVE

LIQUID

TUBING

LIQUID

SHUT-OFF

VALVE

SCHRADER

VALVE

FILTER

DRIER

SCHRADER

VALVE

SOLENOID

VALVE

SIGHT

GLASS

EXPANSION

VALVE

WATER INWATER OUT

DX EVAPORATOR

FIELD CONNECTION

SUCTION LINE

SUCTIONSHUT-OFF

VALVE

SUCTION

TUBING

SCHRADER

VALVE

DISCHARGE

TUBING

AIR

FLOW

AIR

FLOW

AIR

FLOW

CONDENSOR

ASSEMBLY

FRAME 3200COMPRESSOR

RELIEF

VALVE

CHARGING

VALVE

RELIEF

VALVE

FIELD CONNECTION

LIQUID LINE

SCHRADER

VALVE

(HEADER)

330591001-R3FACTORY PIPING FIELD PIPING

DISCHARGECHECK ANDSHUT-OFF

VALVE

NOTE: The above figure illustrates the piping for the remote evaporator option. For the standard packaged

version, the field piping shown as dotted would be installed in the factory.

OM AGSD3 17

Controller Operation

CP1 Inputs/Outputs

I/O for the unit control and for circuits one and two are found on CP1.

Analog Inputs

# Description Signal Source Normal Range

1 Slide Load Indicator #1 4-20 mA Current 1 to 23 mA


3 Evaporator Pressure #1 4-20 mA Current 3 to 22 mA

4 Discharge Temperature #1 PT1000 Sensor -45 to 240°F


6 Condenser Pressure #1 4-20 mA Current 3 to 22 mA

7 Condenser Pressure #2 4-20 mA Current 3 to 22 mA

8 Evaporator Pressure #2 4-20 mA Current 3 to 22 mA

9 Evaporator Entering Water Temp NTC Thermister -45 to 212°F

10 Evaporator Leaving Water Temp NTC Thermister -45 to 212°F

Analog Outputs

# Description Output Signal Range

1 VFD #1 0-10VDC 0 to 100% (1000 steps resolution)

2 EXV #1 0-10VDC 0 to 6386 steps (1000 steps resolution)



5 Reserved for Ceechina VFD#1 (future) 0-10VDC 0 to 100% (1000 steps resolution)

6 Reserved for Ceechina VFD#2 (future) 0-10VDC 0 to 100% (1000 steps resolution)

Digital Inputs

# Description Signal Off Signal On

1 Circuit Switch #1 Cir 1 disabled Cir 1 enabled


3 Evaporator Water Flow Switch No Flow Flow

4 PVM/GFP #1 Fault No Fault

5 Mode Switch Cool mode Ice mode

6 Mechanical High Pressure Switch #1 Fault No Fault


8 Open

9 Open

10 VFD Fault #1 Fault No Fault


12 Starter Fault #1 Fault No Fault

13H Low Pressure Switch #1 Fault No Fault



16 Unit Switch Unit disabled Unit enabled

17 Remote Switch Unit disabled Unit enabled


18 OM AGSD3

Digital Outputs

# Description Output OFF Output ON

1 SSS Enable Compressor Off Compressor On

2 SV Load Off Load

3 SV Unload Off Unload

4 Open

5 SV Liquid Line Off Enabled

6 Fan motor 11/VFD enable Off Fan on

7 Fan motor 12 Off Fan on

8 Fan motor 13/14 Off Fans on


10 SV Load Off Load


12 EXV close #1 Open Pumpdown


14 Open

15 SV Liquid Line Off Fans on

16 Fan motor 21/VFD enable Off Fans on

17 Fan motor 22 Off Fans on


Expansion I/O Controller 1

EXB1 is connected to CP1 for additional I/O.

Analog Inputs

# Description Signal Source Expected Range

1 Suction Temperature #1 NTC Thermister -45 to 195°F


3 Ambient Temperature NTC Thermister -45 to 195°F

4 Open

Analog Outputs


1 Open

Digital Inputs


1 Thermistor Fault #1 Fault No fault 2 Thermistor Fault #2 Fault No fault 3 Open 4 Open

Digital Outputs

# Description Output Off Output On

1 Evap Water Pump Output #1 Pump Off Pump On 2 Remote Alarm Bell Alarm Off Alarm On 3 SV Economizer #1 Off Enabled 4 SV Economizer #2 Off Enabled

OM AGSD3 19



Analog Inputs


1 Chilled Water Reset 4-20 mA Current 4 to 20 mA

2 Demand Limit 4-20 mA Current 4 to 20 mA

3 Oil Pressure #1 4-20 mA Current 3 to 22 mA


Analog Outputs


1 Open

Digital Inputs


1 Open 2 External Alarm Alarm active Alarm not active 3 Open 4 Open

Digital Outputs


1 Fan motor 15/16 Fans Off Fans On

2 Fan motor 17/18/19 Fans Off Fans On

3 Fan motor 25/26 Fans Off Fans On

4 Fan motor 27/28/29 Fans Off Fans On



Analog Inputs

# Description Signal Source Range

1 Open

2 Open

3 Open

4 Open

Analog Outputs


1 Open

Digital Inputs


1 Pump #1 alarm Pump Failure Pump OK

2 Pump #2 alarm Pump Failure Pump OK

3 Open

4 Open

Digital Outputs


1 Evap Water Pump Output #2 Pump Off Pump On

2 Compressor Status Enable #1 Compressor Off Compressor On



20 OM AGSD3

Controller CP2

I/O for circuit three (applies to AG S330D to 450D) are found on CP2.

Analog Inputs

# Description Signal Source Normal Range


2 Open

3 Suction Pressure #3 4-20 mA Current 3 to 22 mA


5 Open

6 Discharge Pressure #3 4-20 mA Current 3 to 22 mA

7 Open

8 Open

9 Open

10 Open

Analog Outputs




3 Open

4 Open

5 Open

6 Open

Digital Inputs



2 Open

3 Open


5 Open mode Ice mode


7 Open

8 Open

9 Open


11 Open No Fault


13 Open


15 Open

16 Open

17 Open

18 Open

OM AGSD3 21

Digital Outputs

# Description Output OFF Output ON


2 SV Load Off Load


4 Open

5 SV Liquid Line Off Enabled

6 Fan motor 31/VFD enable Off Fan on

7 Fan motor 32 Off Fan on


9 Open

10 Open

11 Open


13 Open

14 Open

15 Open

16 Open

17 Open

18 Open



Analog Inputs

# Description Signal Source Range


2 Open

3 Open

4 Open

Analog Outputs


1 Open

Digital Inputs


1 Thermistor Fault #2 Fault No Fault

2 Open

3 Open

4 Open

Digital Outputs


1 Open

2 Open

3 SV Economizer #3 Off Enabled

4 Open

22 OM AGSD3



Analog Inputs


1 Open

2 Open


4 Open

Analog Outputs


1 Open

Digital Inputs


1 Open

2 Open

3 Open

4 Open

Digital Outputs



2 Fan motor 37/38/39 Off Fans on

3 Open

4 Open

Setpoints All setpoints are made on CP1, including circuit 3 settings on three-compressor units.

The following parameters are remembered during power off, are factory set to the Default

value, and can be adjusted to any value in the Range column.

The PW (password) column indicates the password that must be active in order to change

the setpoint

Description Default Range PW

Unit

Unit Enable OFF OFF, ON O

Unit Mode Cool Cool, Ice, Test O

Control source Switches Switches, Keypad, Network O

Available Modes Cool Cool, Cool w/Glycol, Cool/Ice w/Glycol, ICE w/Glycol, TEST

M

Cool LWT (25°F With Glycol) 44 °F 25 (40) to 60 °F O

Ice LWT 25 °F 20 to 38°F O

Startup Delta T 10 °F 0 to 10 °F O

Stop Delta T 1.5 °F 0 to 3 °F O

Stage Up Delta T 2 °F 0 to 3 °F O

Stage Down Delta T 1 °F 0 to 3 °F O

Max Pulldown 5 °F/min 0.5-5.0 °F /min M

Evap Recirc Timer 30 0 to 300 seconds M

Evap Pump Select #1 Only #1 Only, #2 Only, Auto, #1 Primary, #2 Primary

M

LWT Reset Type NONE NONE, RETURN, 4-20mA, OAT M

Max Reset 0 °F 0 to 20 °F M

Continued on next page.

OM AGSD3 23


Start Reset Delta T 10 °F 0 to 20 °F M

Soft Load Off Off, On M

Begin Capacity Limit 40% 20-100% M

Soft Load Ramp 20 min 1-60 minutes M

Demand Limit Off Off, On M

# of Circuits 2 2-4 O

Low Ambient Lockout 55 °F -10 (35) to 70 °F M

Ice Time Delay 12 1-23 hours M

Clear Ice Timer No No,Yes M

SSS Communication No No, Yes M

PVM Multi Point Single Point, Multi Point ,

None(SSS) O

Quiet Night Disabled Disabled, Enabled M

Quiet Night Start Time 21:00 18:00 - 23:59

Quiet Night End Time 6:00 5:00 – 9:59

Quiet Night Condenser Offset 10.0°F 0.0 – 25.0°F

BAS Protocol Modbus BACnet, LonWorks, Modbus M

Ident number 1 0-200 M

Baud Rate 19200 1200,2400,4800,9600,19200 M

Evap LWT sensor offset 0 -5.0 to 5.0 deg M

Evap EWT sensor offset 0 -5.0 to 5.0 deg M

OAT sensor offset 0 -5.0 to 5.0 deg M

Compressors-Global

Start-start timer 20 min 15-60 minutes M

Stop-start timer 5 min 3-20 minutes M

Pumpdown Pressure 25 psi 10 to 40 psi M

Pumpdown Time Limit 120 sec 0 to 180 sec M

Light Load Stg Dn Point 25% 20 to 50% M

Stage Up Delay 5 min 0 to 60 min M

Max # Comps Running 3 1-3 M

Sequence # Cir 1 1 1-3 M

Sequence # Cir 2 1 1-3 M

Alarm Limits

Low Evap Pressure-Unload 28 psi 0(26) to 45 psi M

Low Evap Pressure-Hold 30 psi 0(28) to 45 psi M

Oil Press Delay 30 sec 10-180 sec M

Oil Press Differential 25 psi 0-60 psi M

High Discharge Temperature 220 °F 150 to 230 F M

High Lift Pressure Delay 5 sec 0 to 30 sec M

Evaporator Water Freeze 36 °F 0 (36) to 42 °F M

Evaporator Flow Proof 3 sec 3 to 10 sec M

Low OAT Start Timer 60 sec 20 to 180 sec M

The following setpoints exist individually for each circuit: Description Default Range PW

Compressor

Circuit mode enable Disable, enable, test M

Slide control auto Auto, manual M

Slide position 0 0-100 M

Compressor Size 167 167, 179, 197, 205, 220, 235 M

Clear Cycle Timers No No, yes M

Maximum Slide Target 100.0 0-100.0% M

EXV control Auto Auto, manual M


24 OM AGSD3


EXV position 0 0-6386 M

Service Pumpdown No No,Yes M

Slide min pos offset 0 -15 to 15% M

Slide max pos offset 0 -15 to 15% M

Evap pressure offset 0 -10.0 to 10.0 psi M

Cond pressure offset 0 -10.0 to 10.0 psi M

Oil pressure offset 0 -10.0 to 10.0 psi M

Suction temp offset 0 -5.0 to 5.0 deg M

Discharge temp offset 0 -5.0 to 5.0 deg M

Fans

Fan VFD enable On Off, On M

Number of fans 6 6 to 9 M

Saturated Condenser Temp Target Min

90.0 80.0-110.0 o

F M

Saturated Condenser Temp Target Max

110.0 90.0-120.0 oF M

Stage 1 On Deadband 5 1.0-20.0 oF M

Stage 2 On Deadband 5 1-20 oF M




Stage 6-8 On Deadband 8 1-20 oF M

Stage 2 Off Deadband 8 1-20 oF M




Stage 6-8 Off Deadband 5 1-20 oF M

VFD Max Speed 100% 90 to 110% M

VFD Min Speed 25% 20 to 60% M

Forced Fantrol 1 2 1 to number of fans M



Auto Adjusted Ranges Some settings have different ranges of adjustment based on other settings. For example, for

the chilled water leaving setpoint range (Cool LWT), if the “Cool” mode is selected, the

range is 40F to 60F. If “Cool w/Glycol” mode is selected, the range is automatically

adjusted to 25F to 60F.

Cool LWT Mode Range

Unit Mode = Cool 40 to 60oF

Unit Mode = Cool w/Glycol 25 to 60oF

Evaporator Water Freeze Mode Range

Unit Mode = Cool 36 to 42oF

Unit Mode = Cool w/Glycol, Ice w/ Glycol 15 to 42oF

Low Evaporator Pressure Inhibit Mode Range

Unit Mode = Cool 28 to 45 Psig

Unit Mode = Cool w/Glycol, Ice w/ Glycol 0 to 45 Psig

Low Evaporator Pressure Unload Mode Range

Unit Mode = Cool 26 to 45 Psig

Unit Mode = Cool w/Glycol, Ice w/ Glycol 0 to 45 Psig

OM AGSD3 25

Dynamic Default Values

The fan staging dead bands have different default values based on the VFD enable setpoint.

When the VFD enable setpoint is changed, a set of default values for the fan staging dead

bands is loaded as follows:

VFD is Enabled VFD is Disabled

Setpoint Default

loaded (oF)

Setpoint

Default

loaded (oF)

Stage 1 On Deadband 8

Stage 2 On Deadband 5 Stage 2 On Deadband 10







Stage 2 Off Deadband 8 Stage 2 Off Deadband 20







26 OM AGSD3

Controller Functions

Parameter Definitions

LWT Slope

LWT slope is calculated so that the slope represents the change in LWT over a time frame of

one minute and is used to help determine the slide valve target.

Every 12 seconds, the current LWT is subtracted from the value 12 seconds back. This

value is added to a buffer containing values calculated at the last five 12-second intervals.

The final result is a slope value that represents the action of the LWT for the past 60

seconds.

Pulldown Rate

The slope value calculated above will be a negative value as the water temperature is

dropping. For use in some control functions, the negative slope is converted to a positive

value by multiplying by –1.

Circuit Capacity

The capacity of each circuit is estimated based on slide position. A circuit that is not

running is always considered to be at 0% capacity. A running circuit can have a capacity

value ranging from 20% to 100%.

The slide position and capacity value for running compressors are related as shown by the

following formula:

Circuit capacity = 0.8(Slide position) + 20

Unit Capacity

For applying unit capacity limits, an estimate of total unit capacity is needed. Unit capacity

will be based on the estimated circuit capacities.

The unit capacity is calculated using the following formula:

Unit capacity = (Circuit 1 capacity + Circuit 2 capacity)/2

Unit Enable Enabling and disabling the chiller is controlled by the Unit Enable Setpoint, with options of

OFF and ON. Enabling allows the unit to start if there is a call for cooling and also starts

the evaporator pump.

This setpoint (in other words, enabling the unit to run) can be altered by the Unit Switch

input (unit On/Off switch), a field installed remote stop switch, a keypad entry, or a BAS

request. The Control Source Setpoint determines which sources can change the Unit Enable

Setpoint with options of SWITCHES, KEYPAD or NETWORK.

Changing the Unit Enable Setpoint can be accomplished according to Table 9

NOTE: An “x” indicates that the value is ignored.

All methods of disabling the chiller, except for the Override Stop switch, will cause a

normal shutdown of any running circuits with pumpdown. Any time the Override Stop

switch is used to disable the chiller, all running circuits will shut down immediately, without

pumping down.

OM AGSD3 27

Table 9, Enable Sources

Unit Switch Input

Control Source

Setpoint

Remote Switch Input

Key-pad Entry

BAS Request

Unit Enable

OFF x x x x OFF

x SWITCHES OFF x x OFF

ON SWITCHES ON x x ON

ON KEYPAD x OFF x OFF

ON KEYPAD x ON x ON

ON NETWORK x x OFF OFF

ON NETWORK OFF x x OFF

ON NETWORK ON x ON ON

Example:

1. If the Control Source is set to Switches, the field-installed remote Stop Switch controls

enabling. If the unit-mounted On/Off switch is either On or Off, the unit will be

disabled if the remote switch is Off. If the unit-mounted On/Off switch is On, the unit

will be enabled if the remote switch is On.

2. With the unit-mounted switch On, if the Control Source is Network, and the BAS signal

is Off, the unit is not enabled. If a Remote Switch is Off, the unit is not enabled. If a

Remote Switch is ON and the BAS input is On, the unit will be enabled.

Chiller Control Source Options:

Set Unit Setpoints Screen #1 (shown below) has three fields: “Enable”, “Mode” and

“Source.”

Unit Setpoints

SET UNIT SPs (1)

Enable=On

Mode= COOL

Source = KEYPAD

1. The Enable field can only be used with Source = Keypad. To enable and disable the

chiller through the keypad, any other control inputs including unit and pumpdown

switches and BAS controls are ignored. The Enable field toggles between On and Off.

2. The Mode field is an informational display, showing the active control mode of the

chiller. It is used as an input only when the source is set to keypad. Only then can this

field be changed manually.

3. The Source field has three options, “SWITCHES”(default), “KEYPAD”, and “BAS

NETWORK”.

a. Switches source is used when there is no BAS interface used. This allows the unit

switches to function as pumpdown and shutdown switches for the circuit. This

option is used with applications using the remote start/stop input and not using a

BAS interface.

b. Keypad source is used to override BAS or remote start/stop commands. This would

be used for servicing only.

c. BAS Network source would be used for those applications using “MODBUS”,

“BACnet”, or “LON” communications through a building automation system. BAS

Protocol is set at Set Unit Setpoints item #14.

28 OM AGSD3

Switches

All methods of disabling the chiller, except for the Override Stop switch, will cause a

normal pumpdown shutdown of any running circuits.

Rapid shutdown by the Override Stop switch without going through the pumpdown cycle is

undesirable and should only be used for an emergency shutdown or for manually and locally

disabling the unit after both circuits have gone through a normal shutdownand the

compressors have stopped.

The unit switch Q0, will perform a pumpdown and shutoff on all running compressors.

The system switches, Q1, Q2, (and Q3) will perform a pumpdown and shutoff on

compressors #1, #2, (or #3).

Unit Mode Selection The overall operating mode of the chiller is set by the Unit Mode Setpoint with options of

COOL, COOL w/Glycol, ICE w/Glycol, HEAT, and TEST. This setpoint can be altered by

the keypad, BAS, and Mode input. Changes to the Unit Mode Setpoint are controlled by

two additional setpoints.

• Available Modes Setpoint: Determines the operational modes available at any time

with options of COOL, COOL w/Glycol, COOL/ICE w/Glycol, and ICE w/Glycol.

• Control Source Setpoint: Determines the source that can change the Unit Mode

Setpoint with options of KEYPAD, NETWORK, or SWITCHES.

When the Control Source is set to KEYPAD, the Unit Mode will stay at its previous setting

until changed by the operator. When the Control Source is set to BAS, the most recent BAS

mode request will go into effect even if it changed while the Control source was set to

KEYPAD or DIGITAL INPUTS.

Changing the Unit Mode Setpoint can be accomplished according to the following table.

NOTE: An “x” indicates that the value is ignored.

Control Source Setpoint

Mode Input

Keypad Entry BAS

Request Available Modes

Setpoint Unit Mode

x x x x COOL

COOL

x x x x COOL w/Glycol COOL w/Glycol

SWITCHES OFF x x COOL/ICE w/Glycol COOL w/Glycol

SWITCHES ON x x COOL/ICE w/Glycol ICE w/Glycol

KEYPAD x COOL w/Glycol x COOL/ICE w/Glycol COOL w/Glycol

KEYPAD x ICE w/Glycol x COOL/ICE w/Glycol ICE w/Glycol

NETWORK x x COOL COOL/ICE w/Glycol COOL w/Glycol

NETWORK x x ICE COOL/ICE w/Glycol ICE w/Glycol

x x x x ICE w/Glycol ICE w/Glycol

x x x x TEST TEST

Unit Test Mode

The unit test mode allows manual testing of controller outputs. Entering this mode requires

the following conditions.

• Unit OFF input = OFF (i.e. entire chiller is shut down).

• Manager password active.

• Available Unit Mode setpoint = TEST

A test menu can then be selected to allow activation of the outputs. It will be possible to

switch each digital output ON or OFF and set the analog outputs to any value.

OM AGSD3 29

Unit States The unit will always be in one of three states. Transitions between these states occur as

shown below.

Power ON OFF

PUMPDOWN AUTO

T1

T4

T2

T3

Unit States

Transitions: T1 – Transition from Off to Auto requires all of the following:

• Unit enabled based on settings and switches.

• If unit mode is ice, the ice timer has expired

• No unit alarms exist.

• At least one circuit is enabled and available to start.

T2 – Transition from Auto to Pumpdown requires any of the following:

• Control source is keypad and the unit enable keypad setting is Off.

• Control source is BAS and either the remote switch is Off or the BAS command is Off

• Control source is switches and the remote switch is Off

• Unit switch Q0 is Off.

T3 – Transition from Pumpdown to Off requires any of the following:

• All circuits have finished pumpdown and are Off.

• A unit alarm is active.

T4 – Transition from Auto to Off requires any of the following:

• A manual reset unit alarm is active

• All circuits are unavailable to start (cannot start even after any cycle timers have

expired)

• The unit mode is ice, all circuits are off, and the ice mode delay is active

30 OM AGSD3

Ice Mode Start Delay An adjustable start-to-start ice delay timer will limit the frequency with which the chiller

may start in Ice mode. The timer starts when the first compressor starts while the unit is in

ice mode. While this timer is active, the chiller cannot restart in Ice mode. The time delay

is user adjustable.

The ice delay timer may be manually cleared to force a restart in ice mode. A setpoint

specifically for clearing the ice mode delay is available. In addition, cycling the power to

the controller will clear the ice delay timer.

Evaporator Pump Control The state-transition diagram shown below controls operation of the evaporator pump.

Table 10, Evaporator Pump States

Power ON OFF

RUN START

T1

T4

T2

T3

Evaporator PumpStates

T5

Transitions:

T1 – Transition from Off to Start requires any of the following

• Unit state = Auto AND If Low OAT Lockout is active then LWT <= 40 °F

• LWT < Freeze setpoint - 1 °F

T2 – Transition from Start to Run

• Flow ok for time > evaporator recirculate time

T3 – Transition from Run to Off requires any of the following

• Unit state = Off AND LWT > Freeze setpoint

• Low OAT Lockout is active AND No compressors running AND LWT > 70°F

T4 – Transition from Start to Off requires any of the following

• Unit state = Off AND LWT > Freeze setpoint

• Low OAT Lockout is active AND No compressors running AND LWT > 70°F

T5 – Transition from Run to Start

• Evaporator flow switch is open AND Evaporator state = Run for time greater than Flow

Proof setpoint

OM AGSD3 31

Pump Selection

The pump output used will be determined by the Evap Pump Control setpoint. This setting

allows the following configurations:

#1 only – Pump 1 will always be used

#2 only – Pump 2 will always be used

Auto – The pump used will be the one with the least run hours

Auto Pump Control Auto control compares the run hours of each pump before there is a need to start a pump,

and the pump with the least hours will be designated as the one to start. The selected pump

output will be ON if the Evap State is set to START or RUN. Both outputs will be OFF if

the Evap State is set to OFF.

Leaving Water Temperature (LWT) Reset The Active Leaving Water setpoint is set to the current Leaving Water Temperature (LWT)

setpoint, unless the unit is in COOL or COOL w/Glycol mode, and any of the reset methods

below are selected. The type of reset in effect is determined by the LWT Reset Type

setpoint. The Active Leaving Water variable is sent to all circuits for capacity control after

the applicable reset is applied. Reset is not available in the ICE mode.

Reset changes at the rate of 0.1°F every 10 seconds.

Reset Type – NONE

The Active Leaving Water variable is set equal to the current LWT setpoint.

Reset Type – RETURN

The Active Leaving Water variable is adjusted by the return water temperature.

Start Reset Delta T

LWT set Point+Max Reset

(54)

LWT Set Point(44)

Return Reset

0

Max Reset

(10)

Evap Delta T (oF)

Active

LWT

(oF)

The active setpoint is reset using the following parameters:

1. Cool LWT setpoint

2. Max Reset setpoint

3. Start Reset Delta T setpoint

4. Evap Delta T

Reset is accomplished by changing the Active Leaving Water variable from the Cool LWT

setpoint to the Cool LWT set-point + Max Reset setpoint as the Evaporator EWT – LWT

(Evap delta t) varies from the Start Reset Delta T set-point to 0.

32 OM AGSD3

Reset Type – 4-20 mA

The Active Leaving Water variable is adjusted by the 4 to 20 mA reset analog input.

Parameters used:



3. LWT Reset signal

Reset is 0 if the reset signal is less than or equal to 4 mA. Reset is equal to the Max Reset

Delta T setpoint if the reset signal equals or exceeds 20 mA. The amount of reset will vary

linearly between these extremes if the reset signal is between 4 mA and 20 mA. An

example of the operation of 4-20 reset in Cool mode is shown below.

20

(54)

Cool LWT SetPoint (44)

4

4-20 mA Reset - Cool Mode

0

Max Reset(10)

ActiveLWT(oF)

Reset Signal (mA)

Reset Type – OAT

The Active Leaving Water variable is reset based on the outdoor ambient temperature.

Parameters used:



3. OAT

Reset is 0 if the outdoor ambient temperature is greater than 75 F. From 75 down to 60 F

the reset varies linearly from no reset to the max reset at 60 F. At ambient temperatures less

than 60 F, reset is equal to the Max Reset setpoint.

75

Cool LWT+Max Reset

(54)

Cool LWT Set-Point

(44)

OAT Reset

60

Max Reset

(10)

OAT (oF)

Active

LWT

(oF)

OM AGSD3 33

Quiet Night Sound Reduction • Quiet Night operation is in effect if it is enabled via the setpoint, the unit is running in

cool mode, and the unit time is between the start and end time settings.

• When Quiet Night is in effect, the maximum LWT reset will be applied. This is to limit

the capacity of the compressors. In addition, the circuits will offset their condenser

targets up. Depending on conditions, this can result in less fans running and/or the VFD

running at a lower speed.

• The unit status will indicate when Quiet Night is in effect (assuming no overriding

status is active).

• The Quiet Night reset will be overridden by any other reset source (4-20mA, return

water, OAT).

Unit Capacity Overrides Unit capacity limits can be used to limit total unit capacity in COOL mode only. Multiple

limits may be active at any time, and the lowest limit is always used in the compressor

capacity control.

The estimated unit capacity and the active capacity limit are sent to all circuits for use in

compressor capacity control.

Soft Load

Soft Loading is a configurable function used to ramp up the unit capacity over a given time.

The setpoints that control this function are:

• Soft Load – (ON/OFF)

• Begin Capacity Limit – (Unit %)

• Soft Load Ramp – (seconds)

The Soft Load Unit Limit increases linearly from the Begin Capacity Limit setpoint to

100% over the amount of time specified by the Soft Load Ramp setpoint. If the option is

turned off, the soft load limit is set to 100%.

Demand Limit

The maximum unit capacity can be limited by a 4-to-20 mA signal on the Demand Limit

analog input at the unit controller. This function is only enabled if the Demand Limit

setpoint is set to ON.

As the signal varies from 4 mA up to 20 mA, the maximum unit capacity changes linearly

from 100% to 0%. Although the demand limit can call for 0% capacity, this signal will

never cause a running compressor to shut down. Rather, all running compressors will be

held at minimum load, and this may occur at a demand limit value that is actually less than

20mA.

Network Limit

The maximum unit capacity can be limited by a network signal. This function is only

enabled if the unit control source is set to network. The signal will be received through the

BAS interface on the unit controller.

As the signal varies from 0% up to 100%, the maximum unit capacity changes linearly from

0% to 100%. Although the network limit can call for 0% capacity, this signal will never

cause a running compressor to shut down. Rather, all running compressors will be held at

minimum load, and this may occur at a network limit value that is actually less than more

than 0%.

34 OM AGSD3

BAS Interface

Connection to Chiller

Connection to the chiller for all BAS protocols is at the unit controller. An interface card

will have to be installed in the unit controller depending on the protocol being used.

Protocols Supported

The following building automation system (BAS) protocols are supported. It is possible to

change the building automation interface without loading different software.

BACnet When protocol is set to BACnet, the baud rate and ident setpoints are not accessible. The

ident setting is locked at 1 for BACnet, and the baud rate is locked to 19200.

LONWORKS With protocol set to LON, the baud rate and ident setpoints are not accessible. The ident

setting is locked at 1 for LON, and the baud rate is locked to 4800.

Modbus With the protocol set to Modbus, the baud rate and ident setpoints are accessible.

Available Parameters

Types: A = Analog, I= Integer, D= Digital

I/O: I = Input only, O = Output only , I/O = Input/Output

Type Index I/O Description LONWORKS BACnet Modbus

A 1 I/O Network Cool LWT setpoint x x x

A 2 O Active LWT setpoint x x x

A 3 I Network Capacity Limit x x x

A 4 O Evap EWT x x x

A 6 O Evap LWT x x x

A 10 O Unit capacity (%) x x x

A 11 I Network Cool LWT setpoint default x

A 15 O Suction Temp x x x

A 16 O Evap sat temp x x x

A 17 O Evap pressure x x x

A 19 O Discharge Temp x x x

A 20 O Cond sat temp x x x

A 21 O Cond pressure x x x

A 31 O Slide Position x x x

A 32 O Oil Pressure x x x

A 39 O OAT x x x

A 42 O Active Capacity Limit x x x

A 50 I/O Network Ice LWT setpoint x x x

I 1 O Active alarms 1 x x x





OM AGSD3 35

Type Index I/O Description LONworks BACnet Modbus













I 17 I Network chiller mode setpoint x x x

I 18 O LON Chiller run mode x x x

I 19 O Active unit mode x x x

I 20 I Network Capacity Limit default setpoint x

I 21 I Network chiller mode default setpoint x

I 22 O CSM unit full load/circuit available status x x x

I 28 O Unit model type, refrigerant x x x

I 29 O Unit language x x x

I 30 O Unit software version x x x

I 32 I Compressor select x x x

I 35 I/O Clock year x x

I 36 I/O Clock month x x

I 37 I/O Clock day of month x x

I 38 I/O Clock day of week x x

I 39 I/O Clock hours x x

I 40 I/O Clock minutes x x

I 45 O Compressor starts x x x

I 46 O Compressor run hours x x x

1 47 O Evaporator Ppump run hours x x x

D 1 I/O Network chiller enable setpoint x x x

D 2 O Chiller enable status x x x

D 3 O Active alarm indicator x x x

D 4 O Chiller run enabled x x x

D 5 O Chiller local control x x x

D 6 O Chiller capacity limited x x x

D 7 O Evaporator Water Flow x x x

D 8 O Condenser Water Flow x x x

D 9 I Network chiller enable default setpoint x

D 10 I Ignore network defaults x

D 12 I Set clock command x x

D 24 I Network clear alarm signal x x x

D 29 O Evaporator pump x x x

Parameter Details

Units of Measure Parameters are expressed in different units depending on the protocol selected.

ParameterType Modbus Units BACnet Units LONWORKS Units

Temperature oF X 10

oF X 10

oC X 100

Pressure PSI X 10 PSI X 10 KPa X 10

Percentage % X 10 % X 10 % X 200

36 OM AGSD3

Chiller Mode Applies to Integer 17 and Integer 19. Network Chiller Mode Setpoint and Active Chiller

Mode use the same numbering scheme to represent ice mode or cool mode. The output

representing the mode is shown below for each protocol.

Mode LONworks BACnet Modbus

Cool 3 2 2

Ice 11 1 1

LON Chiller Run Mode Applies to Integer 18. The LON Chiller Run Mode parameter indicates the unit state as

follows:

State LONworks BACnet Modbus

Off 0 1 1

Run 2 3 3

Pumpdown 3 4 4

Service 4 5 5

State = Off any time the state is not Run or Service

State = Run when the unit state is Auto

State = Service when the unit is in Test mode

Unit Identification Integer 28 indicates the unit model type and refrigerant. For the AGS with R-134a

refrigerant the output is 10.

Integer 29 indicates the unit language. For the AGS the language can only be English, so

output is 1.

Integer 30 indicates the software version and revision. The hundreds digit represents the

version, and the remaining part represents the revision letter.

Compressor Select Compressor Select is used to select the compressor for which the associated parameters will

be sent to the BAS interface. The input should equal the number of the compressor for

which data is desired. If a 0 is sent from the BAS, this will also select compressor 1.

Timeclock Setting The chiller time and date may be changed through the BAS interface. Time and date are

updated by first setting the values for the time and date inputs on the BAS. When the BAS

sets digital index 12 high, the time and date in the controller is set to the values supplied by

the BAS. The values used are as follows:

Year: Integer # 35 (00 to 99)

Month: Integer # 36 (1 to 12)

Day of Month: Integer # 37 (1 to 31)

Day of Week: Integer # 38 (1 to 7)

Hour: Integer # 39 (0 to 23)

Minute: Integer # 40 (0 to 59)

OM AGSD3 37

Network Defaults The network setpoint default values are used only for the LONWORKS protocol. Digital

index 10 determines whether the network defaults should be loaded at startup. The startup

process is as follows.

Immediately after the controller powers up, the protocol is checked. If the protocol is

LONWORKS, then the current status of the BAS unit enable setpoint, digital 1, is stored in a

temporary location and the BAS enabled setpoint is set to disable. A ten-second timer

should lapse, then the “ignore network defaults” setting is checked. If this is set low, then

the defaults for BAS cool setpoint, network limit, unit enable, and unit mode will be loaded.

If the setting is set high, then no defaults are loaded and the status of the BAS enable

setpoint is restored to the original value.

Unit Full Load/Circuit Available Status for CSM A unit full load flag and circuit available flags are set for use by the CSM. These flags tell

the BAS system when the unit is running at the maximum available capacity, and which

circuits are available to the BAS for more capacity.

The full load flag is set when either of the following are true:

• -Each circuit is either running at maximum capacity or is disabled

• -Unit capacity is greater than or equal to the unit capacity limit

The circuit available flag for each circuit is set when all the following are true:

• -Circuit is communicating on pLAN

• -Unit Control Source = BAS

• -[Remote switch is closed AND Unit switch is closed AND Unit state = Off] OR

Unit state = Auto

• -Low OAT lock condition does not exist

• -Circuit is enabled

The unit full load flag is represented by bit 0 of integer index 22. Circuit one available flag

is represented by bit 1, and circuit two available flag is represented by bit 2.

Digital Output Parameters

Type Index I/O Description Details

D 2 O Chiller enable status Set whenever the chiller is enabled by all settings and switches

D 3 O Active alarm indicator Set when any alarm is active. Active events do not set this output

D 4 O Chiller run enabled Set when the unit state is auto

D 5 O Chiller local control Set when the unit control source is set to keypad or switches.

D 6 O Chiller capacity limited Set when a unit capacity limit is active, any circuit is disabled, or

any circuit is limited in capacity.

D 7 O Evaporator water flow Set when evaporator flow switch is closed

The MicroTech II controller is equipped with the Open Choices feature, an exclusive

McQuay feature that provides easy unit interface with a building automation system (BAS).

If the unit will be tied into a BAS, the controller should have been purchased with the

correct factory-installed communication module. The modules can also be added in the

field during or after installation.

38 OM AGSD3

If a communication module was ordered, one of the following BAS interface installation

manuals was shipped with the unit. Contact your local McQuay sales office for a

replacement, if necessary or obtain from www.mcquay.com.

• IM 735, LONWORKS Communication Module Installation

• IM 736, BACnet MSTP Communication Module Installation

• IM 837, BACnet IP/Ethernet Communication Module Installation

• IM 743, Modbus Communication Module Installation

• ED 15062, Microtech II Chiller Protocol Information – BACnet MSTP and

LONWORKS

• ED 15063, Microtech II Chiller Unit Controller Protocol Information – Modbus

• ED 15100, Microtech II Chiller Protocol Information – BACnet IP/Ethernet

OM AGSD3 39

Circuit Functions

Calculations

Refrigerant Saturated Temperature

Refrigerant saturated temperature is calculated from the pressure sensor readings for each

circuit. The pressure is fitted to a curve made up of 12 straight-line segments. The points

used to define these segments are shown in the following tables.

Evaporator Pressure Conversion:

Pressure (PSI) Temperature (oF)

0 -15.0

7.1 0

19.0 20.0

34.7 39.0

50.7 54.0

70.4 69.0

99.6 87.0

129.2 102.0

166.8 118.0

205.4 132.0

246.5 145.0

320.0 165.0

428.5 188.1

Condenser Pressure Conversion:

Pressure (PSI) Temperature (oF)

0 0.6

17.5 18.5

31.5 35.9

50.0 53.7

76.0 73.4

115.0 95.6

161.5 116.2

185.0 125.2

260.0 149.2

284.5 155.9

349.5 172.0

365.5 175.5

428.5 188.1

Evaporator Approach

The evaporator approach is calculated for each circuit. The equation is as follows:

Evaporator Approach = LWT – Evaporator Saturated Temperature

Suction Superheat

Suction superheat is calculated for each circuit using the following equation:

Suction superheat = Suction Temperature – Evaporator Saturated Temperature

40 OM AGSD3

Discharge Superheat

Discharge superheat is calculated for each circuit using the following equation:

Discharge superheat = Discharge Temperature – Condenser Saturated Temperature

Oil Differential Pressure

Oil Differential Pressure is calculated for each circuit with this equation:

Oil Differential Pressure = Discharge Pressure – Oil Pressure

Compressor Control

Next On / Next Off

This section defines which compressor is the next one to start or stop. In general,

compressors with fewer starts will normally start first, and compressors with more run hours

will normally stop first. Compressor start sequence can also be determined by an operator-

defined sequence.

Next On Only circuits that are available to start immediately are eligible to be next on.

• The circuit with the lowest sequence number should be next on.

• If the sequence numbers are all the same, the circuit with the lowest number of

starts should be next on.

• If the starts are equal and the sequence numbers are all the same, the circuit with the

lowest number of run hours should be next on.

• If the run hours are equal, the sequence numbers are all the same, and the run hours

are all the same, then the lowest numbered circuit should be next on.

Next Off • Only circuits that are currently in the run state are eligible to be next off.

• The circuit with the lowest sequence number should be next off.

• If the sequence numbers are all the same, the circuit with the highest run hours

should be next off.

• If the run hours are equal and the sequence numbers are all the same, the lowest

numbered circuit should be next off.

Required Parameters 1. Sequence number setpoint for all compressors.

2. Number of starts for all compressors.

3. Number of run hours for all compressors.

4. Status of all compressors (Available/Unavailable, Pumping down, Running, etc.).

OM AGSD3 41

Start/Stop Timing – Cool Mode

This section defines when a compressor is to start or stop, when the chiller is operating in

cool mode.

Each circuit looks at all the required parameters independently to determine if it is time to

stage up or stage down.

Required Parameters Startup Delta T setpoint.

Stage-Up Delta T setpoint

Stage-Down Delta T setpoint

Stop-Delta T setpoint

LWT error

Full load indicator for each compressor

Stage-Up Delay setpoint

Light Load Stage-Down setpoint

Full Load Indicator A circuit is considered to be at full load in the compressor staging logic when any of the

following occur:

• Slide control = manual

• A low or high pressure limit event has been active for 10 seconds

• Slide target >= 75% AND max slide target > 75%

• Slide target >= max slide target AND max slide target <= 75%

Stage-Up Delay There is a stage-up delay after starting the first compressor. After the first compressor

starts, a time equal to the stage-up delay setpoint must pass before the next compressor is

allowed to start.

The delay only applies when a compressor is already running. If the first compressor starts

and very quickly fails on alarm or some other event shuts it off, then the other compressor

may start without the delay.

Light Load Stage-Down When multiple compressors are running and they are all at a low capacity, more efficient

operation can be achieved by shutting down a compressor and allowing the remaining

compressor to increase in capacity to handle the load.

If all running compressors have slide targets less than the Light-Load Stage-Down setpoint

and the LWT is less than the active LWT setpoint plus the Stage-Up Delta T setpoint, then

the stage down should occur.

Multiple Compressor Start/Stop Timing – Ice Mode

This section defines when a compressor is to start or stop when the chiller is operating in ice

mode.

Required Parameters Startup Delta T setpoint.

Stage Up Delta T setpoint

LWT error (See definition under Compressor Capacity Control section.)

42 OM AGSD3

Compressor Capacity Control Compressor capacity is determined by calculating a slide position target. Adjustment to the

slide target for normal running conditions occurs every 5 seconds. For loading a maximum

change of 1% is allowed, and for unloading a maximum change of 2% is allowed.

Required parameters Count In Load Balance status for each compressor

Slide targets of all compressors

LWT error

LWT slope

Count In Load Balance Flag A circuit will be counted for load balancing only if all of the following are true:

• Compressor state is run

• Compressor is able to load up (no limits in effect due to pressure or superheat)

• Slide control is auto

• Slide position target is less than the max slide target setpoint

Cool Mode When the chiller is in COOL mode, capacity of the compressor is adjusted to maintain

leaving water temperature at the Active LWT setpoint, while balancing the load between

running circuits. Load balance offset, lwt error, and lwt slope are used to calculate a change

in slide position as described below.

Load balance offset:

IF other compressor is flagged to be counted in load balance

THEN Load Balance Offset = slide target - ((cir 1 target + cir 2 target + cir 3 target)/3)

ELSE Load Balance Offset = 0

LWT Error:

LWT Error = (Leaving Evaporator Water Temp) – (Active LWT setpoint).

LWT slope:

Slope (deg/minute) = sum of last five LWT changes as calculated every 12 seconds

Slide target adjustment = [LWT Error + (LWT Slope x 4) – Load Balance Offset] / #

Compressors Running

Ice Mode

In ICE mode, the compressor capacity is increased at the maximum rate continuously until

reaching the maximum slide position. Load balancing, LWT error, and LWT slope are

ignored.

Low OAT Start Logic

In order to avoid evaporator low-pressure alarms at the start of a circuit in cold climates, a

low OAT start logic is introduced. It allows the circuit to operate at low evaporator

pressures for a longer time than normal as well as multiple start attempts.

A low OAT start is initiated if the condenser saturated temperature is less than 60°F when

the compressor starts. Once this happens, the circuit is in this low OAT start state for a time

equal to the low OAT start timer setpoint. During this time, the freezestat logic and the low-

pressure events are disabled. The absolute limit of –10 psi is still enforced.

OM AGSD3 43

At the end of the low OAT start, the evaporator pressure is checked. If the pressure is

greater than or equal to the low evaporator pressure unload setpoint, the start is considered

successful. If the pressure is less than the unload setpoint, the start is not successful and the

compressor will stop. Three start attempts are allowed before tripping on the restart alarm,

so if on the third attempt the start is not successful the restart alarm is triggered.

Capacity Overrides – Limits of Operation

The following conditions override the automatic slide control when the chiller is in COOL

mode. These overrides keep the circuit from entering a condition in which it is not

designed to run. Any compressor running with capacity limits because of these conditions

may be considered to be at full load in the compressor staging logic.

Low Evaporator Pressure If the evaporator pressure drops below the Low Evaporator Pressure Hold setpoint while the

compressor is running, the Low Evaporator Pressure Inhibit event is triggered. When

triggered, the compressor will not be allowed to increase in capacity.

If the evaporator pressure drops below the Low Evaporator Pressure Unload setpoint while

the compressor is running, the Low Evaporator Pressure Unload event is triggered. When

triggered, the compressor will begin reducing capacity. The maximum allowed slide target

will be adjusted down 5% every 5 seconds until the evaporator pressure rises above the Low

Evaporator Pressure-Unload setpoint.

These events are logged to an event log when they occur. Both remain active until the

evaporator pressure rises above the hold setpoint plus 2 psi or the circuit goes to a state

other than Run.

High Lift Pressure If the compressor is running and the condenser pressure rises above the High Lift Pressure

Hold setpoint, the High Lift Pressure Inhibit event is triggered. When this happens, the

compressor will not be allowed to increase capacity. This event is active until the condenser

pressure drops 10 psi below the hold setpoint.

If the compressor is running above minimum load capacity and the condenser pressure rises

above the High Lift Pressure Unload setpoint, the High Lift Pressure Unload event is

triggered. When this happens, the compressor will begin reducing capacity. The maximum

allowed slide target will be adjusted down 5% every 5 seconds until the condenser pressure

drops below the High Condenser Pressure Unload setpoint. The compressor will not be

allowed to increase in capacity until the condenser pressure drops to 10 psi below the unload

setpoint.

Low Discharge Superheat Unload If the circuit is running and the low pressure inhibit event is active, the compressor will

unload when the discharge superheat drops below 20 degrees. The unloading will occur by

adjusting the slide target down by 2% every 10 seconds.

Maximum LWT Pulldown Rate

The maximum rate at which the leaving water temperature can drop is limited by the

Maximum Rate setpoint, only when the LWT is less than 60°F. A slope unload factor is

used to reduce the slide target if the pulldown rate exceeds the Maximum Rate setpoint.

Slope Unload Factor: Maximum Rate + LWT slope

If the pulldown rate is too fast, then the slide adjustment made will be equal to the slope

unload factor.

44 OM AGSD3

High Water Temperature Capacity Limit

If the evaporator LWT exceeds 65°F, compressor slide position is limited to a maximum of

75%. Compressors unload to 75% or less if running at greater than 75% slide position when

the LWT exceeds the limit. This feature is to keep the circuit running within the capacity of

the condenser coil.

Unit Capacity Overrides

Unit capacity limits override the automatic slide control when the chiller is in COOL mode

only. The active capacity limit, as well as the estimated unit capacity, will be calculated in

the unit controller and sent to all circuits.

If the unit capacity is greater than the active capacity limit, then no circuit will increase slide

position. If the unit capacity is greater than the active limit plus 1%, the circuits will unload

until the unit capacity is less than 1% greater than the active limit.

Pumpdown When a circuit reaches a condition where the compressor needs to shut down normally, a

pumpdown will be performed. The slide target will automatically go to 0 while pumping

down, and the compressor will run until the pumpdown pressure has been reached, or the

pumpdown time has been exceeded.

Service Pumpdown If the option for a service pumpdown is enabled, then on the next pumpdown the pressure

setpoint will be 5 psi. The circuit will pump down to this pressure and shut off. When the

compressor has completed the service pumpdown, the setpoint is reset to no.

Slide Positioning

Slide Position Indicator Each compressor estimates its slide load percentage from the present value of the slide

position indicator. The percentage is based on the mA signal from the slide load indicator

as shown in the following table.

Compressor Size mA at 0% Slide Indicator mA at 100% Slide Indicator

205 4.94 14.6

220 4.62 17.0

235 4.32 19.4

Load/Unload The load output will remain on when all of the following conditions are true:

• Compressor state is not Off

• The slide position target = 100%

The unload output will remain on when all of the following conditions are true:

• Compressor state is not Off

• Slide position target = 0%

If the slide position target is more than 0% and less than 100% while the compressor state is

not off, the load and unload outputs will pulse as needed. Pulses take place every 6 seconds.

Slide Upper Limit = Slide Position Target + 3%

Slide Lower Limit = Slide Position Target – 3%

Slide Change = Slide Position – Slide Position 1 second back

OM AGSD3 45

The load output will be pulsed on for 100ms when either of the following conditions are

true:

• Slide Change <= 0 AND Slide Position < Slide Lower Limit

• Slide Position < Slide Lower Limit – 10%

The unload output will be pulsed on for 300ms when either of the following conditions are

true:

• Slide Change >= 0 AND Slide Position > Slide Upper Limit

• Slide Position > Slide Upper Limit + 10%

Manual Slide Control Mode

The slide position on each circuit may be controlled manually. A setting on the compressor

setpoints screen in each circuit controller allows the operator to select manual slide control.

On the same screen, a slide target can be selected, from 0% to 100%. Manual slide control

can be selected whether the compressor is running or not.

Anytime a circuit is in manual slide control, it is considered to be at full load in the staging

logic. It also will not be considered a running compressor for load balancing purposes.

None of the capacity limits outlined above will apply in manual slide control, but all stop

alarms are still applicable.

Slide control will revert back to automatic control if a stop alarm occurs while the

compressor is running, or the slide control has been manual for four hours.

Condenser Fan Control The compressor must be running in order to stage fans on. All running fans will turn off

when compressor goes to the off state.

Saturated Condenser Temperature Target

The condenser fan control logic will attempt to control the saturated condenser temperature

to a calculated target. A base condenser target is calculated based on evaporator saturated

temperature. The equation is:

Base saturated condenser target = 5/6 (saturated evaporator temperature) + 68 1/3

This value is then limited to a maximum and minimum determined by the condenser target

max and min setpoints. If these setpoints are both set to the same value, then the saturated

condenser temperature target will be locked at that value.

VFD (Optional)

Condenser pressure trim control is accomplished using an optional VFD on one fan. This

VFD control uses a proportional integral function to drive the saturated condenser

temperature to a target value by changing the fan speed. The target value is normally the

same as the saturated condenser temperature target setpoint.

VFD State The VFD will be started when all the following conditions are true:

• Compressor State is not Off

• Fan VFD is enabled

• Saturated Condenser Temp >= Saturated Condenser Temp Target

• Fan speed output = 0

The VFD will be turned off when either of the following conditions are true:

46 OM AGSD3

• Fantrol fans on = 0 AND Fan speed output = min speed setpoint AND Condenser

Saturated Temp < 70 °F

• Compressor State = Off

Stage Up Compensation In order to create a smoother transition when another fan is staged on, the VFD compensates

by slowing down initially. This is accomplished by adding the new fan stage up deadband

to the VFD target. The higher target causes the VFD logic to decrease fan speed. Then,

every 5 seconds, 0.5 degrees F is subtracted from the VFD target until it is equal to the

saturated condenser temperature target setpoint. This will allow the VFD to slowly bring

the saturated condenser temperature back down.

Fan Stages With or Without VFD Option

There are up to 8 stages of Fantrol available. When the VFD option is selected, the fan

stage 1 is VFD enable.

Fan Staging For a 6 or 9 Fan Circuit:

Fantrol Stage Fans On

1 1

2 1,2

3 1,3,4

4 1,2,3,4

5 1,3,4,5,6

6 1,2,3,4,5,6

7 1,2,5,6,7,8,9

8 1,2,3,4,5,6,7,8,9

Fan Staging For a 7 Fan Circuit:


1 1

2 1,2

3 1,3,4

4 1,2,3,4

5 1,3,4,5,6

6 1,2,3,4,5,6

7 1,2,3,4,5,6,7

Fan Staging For a 8 Fan Circuit:


1 1

2 1,2

3 1,3,4

4 1,2,3,4

5 1,3,4,5,6

6 1,2,3,4,5,6

7 1,3,4,5,6,7,8

8 1,2,3,4,5,6,7,8

Staging Up There are six Stage-Up dead bands that apply to the Fantrol stages. Stages one through five

use their respective dead bands. Stage six to eight share the sixth Stage-Up dead band.

When the saturated condenser temperature is above the Target + the active deadband, a

Stage-Up error is accumulated.

OM AGSD3 47

Stage-Up Error Step = Saturated Condenser Refrigerant temperature – (Target + Stage-Up

dead band)

The Stage-Up Error Step is added to Stage-Up Accumulator once every Stage-Up Error-

Delay seconds. When the Stage-Up Error Accumulator is greater than the Stage-Up Error

SetPoint another stage is added.

When a Stage-Up occurs or the saturated condenser temperature falls back within the Stage-

Up dead band, the Stage-Up Accumulator is reset to zero.

Forced Fan Stage At Start Fans may be started simultaneously with the compressor based on outdoor ambient

temperature. When the compressor starts, a Fantrol stage is forced based on the following

table. Since this logic applies only to Fantrol fans, the VFD fan is not affected.

OAT Fantrol Stage At Start

> 75 oF Forced Fantrol 1 SP



Staging Down There are four Stage-Down dead bands. Stages one through three use their respective dead

bands. Stages four to eight share the fourth Stage-Down dead band.

When the saturated condenser refrigerant temperature is below the Target – the active

deadband, a Stage Down error is accumulated.

Stage-Down Error Step = (Target – Stage-Down dead band) - Saturated Condenser

Refrigerant temperature

The Stage-Down Error Step is added to Stage-Down Accumulator once every Stage-Down

Error Delay seconds. When the Stage-Down Error Accumulator is greater than the Stage-

Down Error Setpoint another stage of condenser fans turned off.

When a stage-down occurs, or the saturated temperature rises back within the Stage-Down

dead band, the Stage-Down Error Accumulator is reset to zero. The accumulator is also

held at zero after startup until either the outside ambient temperature is less than or equal to

75°F, or the saturated condenser temperature is greater than the condenser target less the

active stage-down deadband.

EXV Control Pressure Control

In pressure control, the evaporator pressure is controlled by the EXV position. The

pressure target varies based on evaporator LWT and discharge superheat values. A PID

logic is used to control the pressure to the target value.

The base pressure target is calculated using the following formula:

Base target = 0.6(LWT) – 2

The base target is limited to a range from the low pressure inhibit setpoint plus 2 psi, up to

52 psi.

The pressure control target may be adjusted if the discharge superheat is not within an

acceptable range. If the superheat is less than 22 degrees F, the base pressure target will be

reduced by a value equal to the low superheat error. If the superheat is more than 40

degrees F, the base pressure target will be increased by a value equal to the high superheat

error. At any time, the adjusted target pressure cannot go below the low pressure inhibit

setpoint or above 52 psi.

48 OM AGSD3

When the EXV transitions to the pressure control state, the target will start at the current

evaporator pressure value. The pressure target will then decrement 0.2 psi every second

until reaching the normal calculated target. If the pressure at transition is less than the

calculated target, then pressure control will start immediately with the calculated target.

Superheat Control

In superheat control, suction superheat is controlled directly by the EXV. The superheat

target varies linearly from 6 to 10 degrees F as discharge superheat changes from 30 to 22

degrees F. A PID logic will be used to control the superheat to the target value.

When the EXV transitions to the superheat control state, the target will start at the current

suction superheat value. This target will then decrement 0.1 degree F every second until

reaching the normal target.

Closed

Any time the EXV is not in pressure control or superheat control, it will be in a closed state.

At this time, the EXV position is 0 steps and the EXV close signal (digital output) is active.

EXV State Transitions

Power ON

Closed

Superheat Pressure

EXV States

T1T4T5

T2

T3

Transitions:

T1 – Transition from Closed to Pressure Control requires all of the following

• Unit State = Auto

• Evap State = Run

• Compressor is available

• Compressor is next on

• Stage up now flag is set

• Compressor State = Off

OM AGSD3 49

T2 – Transition from Pressure Control to Superheat Control requires all of the following

• Suction Superheat >= Superheat target

• Evap LWT <= 60 F

• EXV State = Pressure AND Discharge Superheat >= 22 F for at least 3 minutes

• Discharge Temperature <= 180 F

• Low Evap Pressure Unload event not active

T3 – Transition from Superheat Control to Pressure Control requires any of the following

• Evap LWT > 63 F

• Low Evap Pressure Unload event active

• Discharge Superheat < 22 F

• Discharge Temperature > 185 F

T4, T5 – Transition from any state to Closed state requires the following

• Compressor State not Run

EXV Control Range

The table below shows the EXV range for each size compressor at minimum and maximum

capacity. The minimum and maximum values vary linearly with slide position, defining a

new EXV control range for every change in slide position.

Compressor Size EXV Slide %

205mm 220mm 235mm

Min 0 Min EXV Pos

Setpoint Min EXV Pos

Setpoint Min EXV Pos

Setpoint

Max 0 3000 3000 3000

Min 100 870 1080 1300

Max 100 3400 4200 5000

Based on the values in the above table, the EXV control range varies as shown in the table

below. The shaded area the control range.

Max EXV@ 100%

100

Max EXV

@ 0%

Min EXV@ 0%

EXV Control Range

0 Slide Position Target (%)

EXV

StepsMin EXV

@ 100%

Manual EXV Control

The EXV position can be set manually. Manual control can only be selected when the

compressor is in the run state. At any other time, the EXV control setpoint is forced to auto.

When EXV control is set to manual, the EXV position is equal to the manual EXV position

setting. If set to manual when the compressor state transitions from run to another state, the

control setting is automatically set back to auto.

50 OM AGSD3

Compressor Status Enable Output

Each circuit will have its own digital output enabled while that circuit is operating. Any

time the compressor starter output is on, the status enable output will be on for that

compressor.

Economizer Control The economizer is activated when the circuit state is Run and the slide position exceeds

95%. It turns back off when either the circuit goes a state other than Run or the slide

position drops below 60%.

Table 11, Economizer Piping

FilterDrier

SV

SV

Economizer

ToEvaporator

ToCompressorInterstage

TXV

EXV

FromCondenser

SV SolinoidValve

BallValve

EXVElectronicExpansionValve

TXVThermalExpansionValve

Legend

OM AGSD3 51

Alarms and Events Situations may arise that require some action from the chiller or that should be logged for

future reference. A condition that causes a shutdown and requires reset is known as an

alarm. Other conditions can trigger what is known as an event, which may or may not

require an action in response. Faults usually cause a shutdown but may not. All stop

alarms and events are logged.

Unit Stop Alarms The alarm output and red button led are turned ON when any stop alarm occurs. They are

turned off when all alarms have been cleared.

Phase Volts Loss/GFP Fault

Alarm description (as shown on screen): Unit PVM/GFP Fault

Trigger: PVM 1 input is low and setpoint is Single-Point

Action Taken: Rapid stop all circuits

Reset: Auto reset when PVM 1 input is high

Evaporator Flow Loss

Alarm description (as shown on screen): Evap Water Flow Loss

Trigger: 1. Evaporator Pump State = Run AND Evaporator Flow Digital Input = No Flow for time >

Flow Proof Setpoint AND at least one compressor running

2: Evaporator Pump State = Start for time greater than Recirc Timeout Setpoint and all

pumps have been tried


Reset: This alarm can be cleared at any time manually via the keypad or via the BAS clear

alarm signal.

If active via trigger condition #1 above:

When the alarm occurs due to this trigger, it can auto reset the first two times each day, with

the third occurrence being manual reset.

For the auto reset occurrences, the alarm will reset automatically when the evaporator state

is Run again. This means the alarm stays active while the unit waits for flow, then it goes

through the recirculation process after flow is detected. Once the recirculation is complete,

the evaporator goes to the Run state which will clear the alarm. After three occurrences, the

count of occurrences is reset and the cycle starts over if the manual reset flow loss alarm is

cleared.

If active via trigger condition #2 above:

If the flow loss alarm has occurred due to this trigger, it is always a manual reset alarm.

Evaporator Water Freeze Protect

Alarm description (as shown on screen): Evap Water Freeze

Trigger: Evap. LWT drops below evap freeze protect setpoint AND Unit State = Auto


Reset: This alarm can be cleared manually via the keypad or via the BAS clear alarm

signal, but only if the alarm trigger conditions no longer exist.

Leaving Evaporator Water Temperature Sensor Fault

Alarm description (as shown on screen): Evap LWT Sens Fault

Trigger: Sensor shorted or open


Reset: This alarm can be cleared manually via the keypad, but only if the sensor is back in

range.

52 OM AGSD3

Outdoor Air Temperature Sensor Fault

Alarm description (as shown on screen): OAT Sensor Fault




range.

EXB Comm Failure on CP1

Alarm description (as shown on screen): No EXB comm CP1

Trigger: CP1 does not have communication with either EXB1 or EXB4 for 60 seconds

after power up. After communication is established, when communication is lost to either

EXB an immediate shutdown occurs.


Reset: Auto clear when EXB1 and EXB4 are communicating with CP1.

Unit Events The following unit events are logged in the event log with a time stamp.

Entering Evaporator Water Temperature Sensor Fault

Event description (as shown on screen): EWT Sensor Fail


Action Taken: Return water reset cannot be used.

Reset: Auto reset when sensor is back in range.

Circuit Stop Alarms All circuit stop alarms require shutdown of the circuit on which they occur. Rapid stop

alarms do not do a pumpdown before shutting off. All other alarms will do a pumpdown.

The red button LED on the circuit controller is turned on when any circuit stop alarm

occurs. It is turned off when all circuit alarms have been cleared. In addition, the alarm

status is sent to the unit control so the alarm output and the red button led on the unit

controller can be energized while alarms are active.

Alarm descriptions apply to both circuits, the circuit number is represented by ‘N’ in the

description.

Phase Volts Loss/GFP Fault

Alarm description (as shown on screen): PVM/GFP Fault N

Trigger: PVM input is low and PVM setpoint = Multi Point

Action Taken: Rapid stop circuit

Reset: Auto reset when PVM input is high

OM AGSD3 53

Low Evaporator Pressure

Alarm description (as shown on screen): Evap Press Low N

Trigger: [Freezestat trip AND Compressor State = Run AND Low OAT Start not active]

OR Evaporator Press < -10 psi

Freezestat logic allows the circuit to run for varying times at low pressures. The lower the

pressure, the shorter the time the compressor can run. This time is calculated as follows:

Freeze error = Low Evaporator Pressure Unload – Evaporator Pressure

Freeze time = 70 – 6.25 x freeze error, limited to a range of 20-70 seconds

When the evaporator pressure goes below the Low Evaporator Pressure Unload setpoint, a

timer starts. If this timer exceeds the freeze time, then a freezestat trip occurs. If the

evaporator pressure rises to the unload setpoint or higher, and the freeze time has not been

exceeded, the timer will reset.


Reset: This alarm can be cleared manually via the Unit Controller keypad if the evaporator

pressure is above –10 psi.

Evaporator Pressure Switch Fault

Alarm description (as shown on screen): Mech Low Pressure Sw N

Trigger: Mechanical Low Pressure switch input is low and Remote Evap setpoint = Yes


Reset: This alarm can be cleared manually via the Unit Controller keypad if the MLP

switch input is high.

High Lift Pressure

Alarm description (as shown on screen): Lift Pressure High N

Trigger: Condenser Saturated Temperature > Max Saturated Condenser Value for time >

High Lift Delay setpoint


Reset: This alarm can be cleared manually via the Unit Controller keypad

Mechanical High Pressure

Alarm description (as shown on screen): Mech High Pressure Sw N

Trigger: Mechanical High Pressure switch input is low


Reset: This alarm can be cleared manually via the Unit Controller keypad if the MHP

switch input is high.

High Discharge Temperature

Alarm description (as shown on screen): Disc Temp High N

Trigger: Discharge Temperature > High Discharge Temperature setpoint AND compressor

is running


Reset: This alarm can be cleared manually via the Unit Controller keypad.

54 OM AGSD3

High Oil Pressure Difference

Alarm description (as shown on screen): Oil Pres Diff High N

Trigger: Oil Press Differential value exceeds the Oil Press Differential setpoint for a time

greater than Oil Press Delay.



Compressor Starter Fault

Alarm description (as shown on screen): Starter Fault N

Trigger: If PVM setpoint = None(SSS): any time starter fault input is open

If PVM setpoint = Single Point or Multi Point: compressor has been running for at least 12

seconds and starter fault input is open



Thermistor Card Fault

Alarm description (as shown on screen): Motor Temp High N

Trigger: Open on digital input: EXB1 ID1(circuit#1) EXB1 ID2(circuit#2) and EXB5

ID1(circuit#3)



Low OAT Restart Fault

Alarm description (as shown on screen): LowOATRestart Fail N

Trigger: Circuit has failed three low OAT start attempts



No Evaporator Pressure Drop After Start

Alarm description (as shown on screen): No Evap Press Drop N

Trigger: After start of compressor, at least a 1 psi drop in evaporator pressure has not

occurred after 15 seconds



No Pressure At Startup

Alarm description (as shown on screen): No Press At Start N

Trigger: [Evap Pressure < 5 psi OR Cond Pressure < 5 psi] AND Compressor start

requested



CP2 pLAN Failure

Alarm description (as shown on screen): pLAN Failure CP2

Trigger: Circuit three controller not found on pLAN for 60 seconds. Only applies to three

circuit chillers with two large controllers.

Action Taken: Rapid stop circuit three

Reset: Auto clear when CP2 is communicating with CP1 via pLAN

OM AGSD3 55

Cir 3 EXB Failure

Alarm description (as shown on screen): no EXB comm Cir 3

Trigger: Either EXB5 or EXB8 controllers are not found on CP2 RS485 for 60 seconds

after power up. After communication is established, when communication is lost to either

EXB an immediate shutdown occurs.

Action Taken: Rapid stop circuit 3

Reset: Alarm can be cleared manually via the keypad, but only if EXB 5 and 8 are

communicating over RS485 to CP2.

Evaporator Pressure Sensor Fault

Alarm description (as shown on screen): EvapPressSensFault N




range.

Condenser Pressure Sensor Fault

Alarm description (as shown on screen): CondPressSensFault N




range.

Oil Pressure Sensor Fault

Alarm description (as shown on screen): OilPressSensFault N




range.

Suction Temperature Sensor Fault

Alarm description (as shown on screen): SuctTempSensFault N




range.

Discharge Temperature Sensor Fault

Alarm description (as shown on screen): DiscTempSensFault N




range.

Slide Position Sensor Fault

Alarm description (as shown on screen): Slide Pos Sens Fault N

Trigger: Sensor shorted or open AND Slide Control set to Auto



range or Slide Control is set to manual.

56 OM AGSD3

pLAN Failure

Alarm description (as shown on screen): pLan Failure

Trigger: pLAN communication from one controller to the other is lost. Only applies to

three circuit chillers.

Action Taken: Rapid stop circuit #3

Reset: This alarm automatically resets when communication with the unit controller is

established. This alarm is not logged.

Circuit Events The following events limit operation of the circuit in some way as described in the Action

Taken section. The occurrence of a circuit event only affects the circuit on which it

occurred. Circuit events are logged in the event log on the unit controller.

Low Evaporator Pressure - Hold

Event description (as shown on screen): EvapPress Low Hold N

Trigger: The low pressure events are not enabled until the compressor has started and the

evaporator pressure has risen above the Low Evaporator Pressure - Hold setpoint. The unit

mode must also be Cool. Then, while running, if evaporator pressure <= Low Evaporator

Pressure - Hold setpoint the event is triggered.

Action Taken: Inhibit loading by only allowing the slide target to be reduced.

Reset: While still running, the event will be reset if evaporator pressure > (Low Evaporator

Pressure - Hold SP + 2psi). The event is also reset if the unit mode is switched to Ice, or the

compressor state is no longer Run.

Low Evaporator Pressure - Unload

Event description (as shown on screen): EvapPressLowUnload N

Trigger: The low pressure events are not enabled until the compressor has started and the

evaporator pressure has risen above the Low Evaporator Pressure - Hold setpoint. The unit

mode must also be Cool. Then, while running, if evaporator pressure <= Low Evaporator

Pressure - Unload setpoint the event is triggered.

Action Taken: Unload the compressor by decreasing the slide target 5% every five seconds

until the evaporator pressure rises above the Low Evaporator Pressure – Unload setpoint.

Reset: While still running, the event will be reset if evaporator pressure > (Low Evaporator

Pressure - Hold SP + 2psi). The event is also reset if the unit mode is switched to Ice, or the

compressor state is no longer Run.

High Lift Pressure - Hold

Event description (as shown on screen): LiftPressHigh Hold N

Trigger: While the compressor is running and unit mode is Cool, if saturated condenser

temperature >= High Saturated Condenser - Hold Value, the event is triggered.

Action Taken: Inhibit loading by only allowing the slide target to be reduced.

Reset: While still running, the event will be reset if saturated condenser temperature <

(High Saturated Condenser - Hold Value – 10oF). The event is also reset if the unit mode is

switched to Ice, or the compressor state is no longer Run.

High Lift Pressure - Unload

Event description (as shown on screen): LiftPressHighUnloadN

Trigger: While the compressor is running and unit mode is Cool, if saturated condenser

temperature >= High Saturated Condenser - Unload Value, the event is triggered.

Action Taken: Unload the compressor by decreasing the slide target 5% every five seconds

until the condenser pressure drops below the High Saturated Condenser - Unload Value.

Reset: While still running, the event will be reset if saturated condenser temperature <

(High Saturated Condenser - Unload Value – 10oF). The event is also reset if the unit mode

is switched to Ice, or the compressor state is no longer Run.

OM AGSD3 57

Slide Position Error

Event description (as shown on screen): Slide Pos Error CirN

Trigger: When compressor is running and the compressor’s slide position indicator is not

within +/- 25% of the slide target value for a period of 5 minutes, the event is triggered.

Action Taken: None

Reset: N/A

Failed Pumpdown

Event description (as shown on screen): Pumpdown Fail Cir N

Trigger: Circuit state = pumpdown for time > Pumpdown Time setpoint

Action Taken: Shutdown circuit

Reset: N/A

Power Loss While Running

Event description (as shown on screen): Run Power Loss Cir N

Trigger: Circuit controller is powered up after losing power while compressor was running

Action Taken: Delay start of compressor by time equal to the Start-Start timer setpoint.

Reset: N/A

VFD Fault

Event description (as shown on screen): VFD Fault Cir N

Trigger: VFD enabled and VFD fault input goes low

Action Taken: None

Reset: N/A

Alarm Logging When an alarm occurs, the alarm type, date, and time are stored in the active alarm buffer

corresponding to that alarm (viewed on the Alarm Active screens) also in the alarm history

buffer (viewed on the Alarm Log screens). The active alarm buffers hold a record of all

current alarms. The active alarms can be cleared by pressing the Enter key when the end of

the list has been reached by scrolling.

A separate alarm log stores the last 25 alarms to occur. When an alarm occurs, it is put into

the first slot in the alarm log and all others are moved down one, dropping the last alarm. In

the alarm log, the date and time the alarm occurred are stored, as well as a list of other

parameters. These parameters include unit state, OAT, LWT, and EWT for all alarms. If

the alarm is a circuit alarm, then the circuit state, refrigerant pressures and temperatures,

EXV control state, EXV position, slide position, and number of fans on are also stored.

The alarm log shows a compressor run timer that tracks how long a compressor runs.

The alarm log has the compressor slide target as a logged parameter.

Event Logging An event log similar to the alarm log holds the last 25 events to occur. When an event

occurs, it is put into the first slot in the event log and all other entries are moved down one,

dropping the last event. Each entry in the event log includes an event description as well as

the time and date of the occurrence. No additional parameters are logged for events.

The event log is only accessible with the Manager password.

58 OM AGSD3

Using the Controller

4x20 Display & Keypad

Layout The 4-line by 20-character/line, liquid crystal display and 6-key keypad for both of the

circuit controller and the unit controller is shown below.

Table 12, Display (in MENU mode) and Keypad Layout

Air Conditioning

ALARMVIEW

SET

<<<

Advanced

Note that each ARROW key has a pathway to a line in the display. Pressing an ARROW

key will activate the associated line when in the MENU mode. There is no display line

associated with the Down Arrow.

Arrow Keys The four arrow keys (UP, DOWN, LEFT, RIGHT) have three modes of use.

1. Scroll between data screens as indicated by the arrows (default mode).

2. Select a specific data screen in a hierarchical fashion using dynamic labels on the right

side of the display (this mode is entered by pressing the MENU key).

3. Change field values in edit mode according to the following table:

LEFT Default (D)

RIGHT Cancel (C)

UP Increment (+)

DOWN Decrement (-)

These four edit functions are indicated by one-character abbreviations on the right side of

the display (this mode is entered by pressing the ENTER key).

Getting Started, Navigating - Press the MENU key to get started. The navigating

procedures are the same for both the unit controller and the circuit controller.

MENU Key The MENU key is used to switch between the MENU mode as shown in Table 12 and the

SCROLL mode as shown in Table 14. The MENU mode is basically a shortcut to specific

groups of menus used for checking ALARMS, for VIEWING information, or to SET

setpoint values. The SCROLL mode allows the user to move about the matrix (from one

menu to another, one at a time) by using the four ARROW keys.

When in the MENU mode (as shown in Table 12), pressing the LEFT ARROW key will

select the ALARM menus, the RIGHT ARROW key will select the VIEW menus and the

Left Arrow Key and

Red Alarm Light

MENU Key

Key-to-Screen Pathway

Arrow Keys (4) Enter Key and Green

Compressor Run Light

OM AGSD3 59

UP key the SET menus. The controller will go the next lower menu in the hierarchy, and

then other menus can be accessed by using the ARROW keys. Pressing the MENU key

from any menu screen will automatically return to the MENU mode as shown in Table 12.

Another way to navigate through the menus is to press the MENU key when in the MENU

mode (as above). This will switch the controller to the SCROLL mode. The controller will

automatically go to the first screen as shown below (the upper-left menu on the menu matrix

shown on page 62. From there, the four ARROW keys can be used to scroll up, down, or

across to any other menu.

Table 13, Shortcut Menus

LEVEL 1 LEVEL 2 LEVEL 3 (No. of Screens)

UNIT VIEW UNIT (2)

CIRCUIT STATUS VIEW CIRCUIT STATUS (9)

REFRIGERANT VIEW REFRIGERANT (7) VIEW

FANS VIEW FANS (2)

COMPRESSOR SPs SET COMPRESSOR SPs (4)

EXV SPs SET EXV SPs (2)

FAN SPs SET FANS SPs (6) SET

SENSOR OFFSETS SET SENSOR OFFSET (3)

TEST MENUS TEST CIRCUIT TEST CIRCUIT (4)

Table 14, Display (in SCROLL Mode) and Keypad Layout

Air Condit ioning

VIEW UNIT STATUSUnit = COOLCompr. #1/#2=OFF/OFFEvap Pump = RUN

Advanced

ENTER Key Pressing the ENTER key changes the function of the ARROW keys to the editing function

as shown below:

LEFT key, Default, changes a value to the factory-set default value.

RIGHT key, Cancel, cancels any change made to a value and returns to the original

setting.

UP key, Increment, increases the value of the setting

DOWN key, Decrement decreases the value of a setting.

These four edit functions are indicated by one-character abbreviation on the right side of the

display (this mode is entered by pressing the ENTER key).

ARROW Keys (4) ENTER Key

MENU Key

60 OM AGSD3

Most menus containing setpoint values have several different setpoints shown on one menu

screen. When in a setpoint menu, the ENTER key is used to proceed from the top line to the

second line and on downward. The cursor will blink at the entry point for making a change.

The ARROW keys (now in the edit mode) are used to change the setpoint as described

above. When the change has been made, press the ENTER key to enter it. Nothing is

changed until the ENTER key is pressed.

For example, to change the chilled water setpoint:

1. Press MENU key to go to the MENU mode (see Table 12, Display (in MENU mode) and

Keypad Layout

2. Press SET (the UP Key) to go to the setpoint menus.

3. Press UNIT SPs (the Right key) to go to setpoints associated with unit operation.

4. Press the DOWN key to scroll down through the setpoint menus to the third menu which

contains Evap LWT=XX.X°F.

5. Press the ENTER key to move the cursor down from the top line to the second line in

order to make the change.

6. Use the ARROW keys (now in the edit mode as shown above) to change the setting.

7. When the desired value is achieved, press ENTER to enter it and also move the cursor

down.

At this point, the following actions can be taken:

1. Change another setpoint in this menu by scrolling to it with the ENTER key

2. Using the ENTER key, scroll to the first line in the menu. From there the ARROW keys

can be used to scroll to different menus.

Security All setpoints on the controller are protected using passwords. Two four-digit passwords

provide Operator and Manager levels of access to changeable parameters. Operator level is

the lowest level of access. Manager level is the next level, and can access Operator level

parameters in addition to Manager level parameters. The password can only be entered at

the unit controller (CP1).

Operator password: 0100

Manager password: 8745

Entering Passwords

Passwords can be entered using the ENTER PASSWORD screen on the unit controller

(CP1), which is the last screen in the Unit SPs column. The password is entered by pressing

the ENTER key, scrolling to the correct value with the UP and DOWN arrow keys, and

pressing ENTER again. The entered password is not shown after the enter key is pressed.

Once the correct password has been entered, the ENTER PASSWORD screen indicates

which password is active (None, Operator, or Manager). If the wrong password is entered, a

message will temporarily appear stating this. If no valid password is active the active

password level displays “None”.

Entering an incorrect password while a password is active will render the active password

inactive. Entering a valid password that is not the same as the active password will result in

the active password level being changed to reflect the new password level.

OM AGSD3 61

Editing Setpoints

Editing Setpoints

After a valid password has been entered at the unit controller (CP1), setpoints can be

changed on CP1 and CP2 if present. If the operator attempts to edit a setpoint for which the

necessary password level is not active, no action will be taken.

Once a password has been entered, it remains valid for 4 hours after the last key-press on

the unit controller.

Clearing Alarms At Unit: Alarms may be cleared at the unit controller if any password level is active. If the

user attempts to clear an alarm while no password is active, then the controller will

automatically go to the ENTER PASSWORD screen. The user can then enter a password

normally, and scroll back to the active alarm column to clear the active alarm(s).

With BAS: A BAS can clear alarms through digital input index 24.

Unit Controller (CP1) Screens Controller CP1 displays most data from each circuit in addition to unit data. Setpoints that

apply to the unit or to all circuits (including circuit #3) can be changed on this controller.

Various menus are shown in the controller display. Each menu screen shows specific

information. In some cases menus are used only to view the status of the unit, in some cases

they are used for checking and clearing alarms, and in some case they are used to set the

setpoint values that can be changed.

The menus are arranged in a matrix of screens across a top horizontal row. Some of these

top-level screens have sub-screens located under them. The content of each screen and its

location in the matrix are shown in Error! Reference source not found.. Each menu

screen’s detailed description begins on page 63.

Table 15, Unit Controller Shortcut Menus

LEVEL 1 LEVEL 2 LEVEL 3 LEVEL 4

STATUS UNIT

TEMP

CIR 1

CIR 2 CIR STATUS

CIR 3

CIR 1

CIR 2 REFRIGERANT

CIR 3

CIR 1

CIR 2

VIEW

FANS

CIR 3

ACTIVE ALARM

LOG

ALARM LIMITS

UNIT SPs

GLOBAL SPs

CIR 1

CIR 2

COMPRESSOR

SPs INDIVIDUAL SPs

CIR 3

CIR 1

CIR 2

SET

FAN SPs

CIR 3

UNIT

CIR 1

CIR 2 TEST

CIR 3

62 OM AGSD3

The ARROW keys on the controller are used to navigate through the menus. The keys are

also used to change numerical setpoint values contained in certain menus.

As an alternate to selecting screens with the menu function, it is possible to scroll through

all of them with the 4 arrow keys. For this use, the screens are arranged logically in a

matrix as shown below.

Table 16, Unit Controller Menu Matrix

VIEW UNIT STATUS

(1)

VIEW UNIT

TEMP (1)

VIEW CIR 1 STATUS

(1)

VIEW CIR 2 STATUS

(1)

VIEW CIR 3 STATUS

(1)

VIEW REFRG CIR 1 (1)



VIEW FANS CIR 1 (1)

.

.

.

.

VIEW UNIT

TEMP (2)

VIEW CIR 1 STATUS

(2)

VIEW CIR 2 STATUS

(2)

VIEW CIR 3 STATUS

(2)

.

.

.

.

.

.

.

.

.

.

.

.

VIEW FANS CIR 1 (2)

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

VIEW UNIT STATUS

(8)




VIEW FANS CIR 2 (1)

VIEW FANS CIR 3 (1)

EVENT LOG (1)

ALARM LOG (1)

ALARM ACTIVE

(1)

SET UNIT SPs (1)

SET COMP SPs GLOBAL

(1)

SET COMP 1 SPs (1)

VIEW FANS CIR 2 (2) VIEW FANS

CIR 3 (2)

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

SET COMP SPs GLOBAL

(2)

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

SET COMP SPs GLOBAL

(3)

.

.

.

.

EVENT LOG (25)

ALARM LOG (25)

ALARM ACTIVE

(n)

SET UNIT SPs (15)

SET COMP SPs GLOBAL

(4)

SET COMP 1 SPs (6)

Screen Hierarchy

Top Level Menu:

< ALARM

< VIEW

< SET

< TEST

Second Level Menus

ALARM menu:

ALARM < ACTIVE

< LOG

<

<

Table Continued

OM AGSD3 63

VIEW menu:

VIEW < UNIT

< CIR STATUS

<REFRIGERANT

< FANS

Third Level Menu

VIEW UNIT menu:

VIEW < STATUS

UNIT < TEMP

<

<

VIEW CIRCUIT STATUS menu:

VIEW CIR < CIR 1

STATUS < CIR 2

<

<

VIEW REFRIGERANT menu:

VIEW REFR < CIR 1

< CIR 2

<

<

SET menu:

SET < ALARM LIMITS

< UNIT SPs

< COMPRESSOR SPs

Screen Definitions

This section contains a description of each menu’s content. The menus are arranged by

column per the matrix on page 62.

View Menus View menus are used only for viewing the status or setting of some parameter, no setpoint

changes can be made here. Numbers in parenthesis, such as (1), (2), are used when more

than one menu is in a column. Changes to setpoints can only be made in the Set menus.

View Unit Status

VIEW UNIT STATUS (1)

{Unit Status}

{Unit Mode}

Evap Pump= {state}

64 OM AGSD3

Unit Status will display one of the following:

Auto Off:Ice Mode Timer Off:All Cir Disabled

Off:Unit Alarm Off:Keypad Disable Off:Remote Switch

Off:BAS Disable Off:Unit Switch Off:Test Mode

Auto:Wait for load Auto:OAT Lockout Auto:Evap Recirc

Auto:Wait for flow Auto:Pumpdown

Unit mode can show ‘Cool Mode’, ‘Ice Mode’, or ‘Test Mode’.

Pump states include Off, Start, and Run.


Softload Limit=XXX.X

Demand Limit= XXX.X

Network Limit= XXX.X

Values are in percent.


Unit Capacity=XXX.X%

Ice Delay= XXh XXm

Unit capacity is based on slide valve(s) position.

Ice delay will be visible only when unit mode is ICE.


CP1 D.O. 111111111

123456789012345678

XXXXXXXXXXXXXXXXXX

The digital output (D.O.) above and input (D.I.) below, status will show either a “0” or a “1”

designating off and on states.


CP1 D.I. 111111111

123456789012345678

XXXXXXXXXXXXXXXXXX


CP1 Analog Outputs

#1=000.0% #2=000.0%

#3=000.0% #4=000.0%


EXB1 {Status}

D.I. 1234 D.O. 1234

XXXX XXXX

OM AGSD3 65

EXB1 status shows whether the pCOe at pLAN address 1 is online or offline. The digital

input and digital output status is shown, with either a “0” or a “1” on the bottom line of the

screen designating off and on states.


EXB4 {Status}

D.I. 1234 D.O. 1234

XXXX XXXX

EXB4 status shows whether the pCOe at pLAN address 4 is online or offline. The digital

input and digital output status is shown, with either a “0” or a “1” on the bottom line of the

screen designating off and on states.

View Unit Temperature

VIEW UNIT TEMP (1)

Evap LWT= XXX.X oF

Evap EWT= XXX.X oF

Active SP= XXX.X oF

VIEW UNIT TEMP (2)

LWT Pulldn= 0.0 oF/m

Evap Delta T= XX.X

OAT= XXX.X oF

View Circuit Status In the following VIEW CIR screens, the N field indicates which circuit (#1, #2, and #3

when applicable) is being viewed.

VIEW CIR N STATUS(1)

{Circuit Status}

Slide Pos= 000.0%

Slide Target=000.0%

Circuit Status will display one of the following:

Off:Ready Off:Stage Up Delay Off:Cycle Timer

Off:Low OAT Lock Off:Keypad Disable Off:Pumpdown Switch

Off:Alarm Off:Test Mode EXV Preopen

Run:Pumpdown Run:Normal Run:LWT PullDn Limit

Run:Unit Cap Limit Run:High LWT Limit Run:Disc SH Low

Run:Evap Press Low Run:Lift Press High Off:pLAN failure

VIEW CIR N STATUS(2)

Hours = XXXXX

Starts = XXXXX

66 OM AGSD3

View Refrigerant In the following VIEW REFR screens, the N field indicates which circuit (#1, #2 and #3

when applicable) is being viewed.

VIEW REFR CIR N (1)

Evap Press=XXX.X psi

Cond Press=XXX.X psi

Oil Press=XXX.X psi

VIEW REFRG CIR N (2)

Sat Evap= XXX.X°°°°F

Sat Cond= XXX.X°°°°F


Suct Temp = XXX.X °°°°F

Disc Temp = XXX.X °°°°F


Suct SH= XXX.X °°°°F

Disc SH= XXX.X °°°°F


Evap Approach=XX.X°°°°F

Cond Approach=XX.X°°°°F

Oil Delta P=XX.X psi


MaxCondSatT=XXX.X °°°°F

EXV Ctrl={EXV State}

EXV State will show one of the following: Closed, Pressure, Superheat.


EXV Steps= XXXX

EXV Ctrl Range:

XXXX – XXXX steps

View Fans

In the following VIEW FANS screens, the N field indicates which circuit is being viewed.

VIEW FANS CIR N (1)

Fans Running=X

Stage Up Err=XXX

Stage Dn Err=XXX

OM AGSD3 67

VIEW FANS (2)

Target Sat T=XXX.X°°°°F

VFD Speed= XXX.X%

VFD Target= XXX.X°°°°F

This screen appears when the VFD is enabled.

Screen Definitions – ALARM

ALARM LOG: XX

{Alarm Description}

hh:mm mm/dd/yy

{Parameters}

Alarm Description will indicate which alarm occurred. If the alarm is a circuit alarm, then

the circuit for which the alarm occurred will also be indicated.

Parameters at the time of the alarm are shown on the bottom line of the screen one at a time.

They are listed below. They are scrolled through by pressing the edit key and using the up

and down arrows to scroll through the list. Parameters include:

Unit State Evap LWT Evap EWT

OAT Circuit State Evaporator Pressure

Condenser Pressure Oil Pressure Suction Temperature

Discharge Temperature Discharge Superheat EXV Position

EXV State Slide Position Fans On

EVENT LOG: XX

{Event Description}

hh:mm mm/dd/yy

*** ALARM ***

hh:mm mm/dd

{Alarm Description}

This screen shows the current alarm, if there is one.

Screen Definitions – SET SETPOINTS

NOTE: All setpoint settings are made in CP1. Additional information on controller inputs

and outputs, as well as setpoint defaults and ranges can be found beginning on page 17.

SET UNIT SPs (1)

Enable=On

Mode= COOL

Source = SWITCHES

SET UNIT SPs (2)

Available Modes

= COOL

Select w/Unit Off

The bottom line is a reminder that the unit must be shut off to change modes.

68 OM AGSD3

SET UNIT SPs (3)

Cool LWT = XX.X°°°°F

Ice LWT = XX.X°°°°F

StartDelta=XX.X°°°°F

SET UNIT SPs (4)

StopDelta= X.X°°°°F

Stg Up Delta= X.X°°°°F

Stg Down Delta=X.X°°°°F

SET UNIT SPs (5)

Max Pulldn=X.X°°°°F/min

EvapRecTimer=XXX sec

Evap Pump= #1 Only

SET UNIT SPs (6)

Reset Type= none

Max Reset = XX.X°°°°F

StrtResetDT= XX.X°°°°F

SET UNIT SPs (7)

Soft Load= Off

Begin Capacity= XXX%

SoftLoadRamp= XXmin

SET UNIT SPs (8)

Demand limit= Off

Low Amb Lock= XX.X°°°°F

Num Circuits – X

Number of circuits determines whether circuit #3 will be visible.

SET UNIT SPs (9)

Ice Time Delay=XXhrs

Clear Ice Timer=No

PVM = Multi Point

Phase Voltage Monitor (PVM) can be single or multi-point and applies to units with wye-

delta starters. Select NONE (SSS) for units with solid-state starters, which have an internal

PVM capability. If NONE (SSS) is not selected for solid-state starter units, the unit will not

operate.

SET UNIT SPs (10)

Remote Evap=No

OM AGSD3 69

SET UNIT SPs (11)

Sensor Offset

Evap LWT= X.X°°°°F

Evap EWT= X.X°°°°F

SET UNIT SPs (12)

Sensor Offset

OAT= XX.X°°°°F

SET UNIT SPs (13)

Quiet Night= Disable

Start @ XX:XX

End @ XX:XX

SET UNIT SPs (14)

Quiet Night

Cond Offset= XX.X°°°°F

SET UNIT SPs (15)

CLOCK

mm/dd/yyyy

hh:mm day

SET UNIT SPs (16)

Units = °°°°F/psi

Lang = ENGLISH

SET UNIT SPs (17)

Protocol=

Ident Number=

Baud Rate=

SET UNIT SPs (18)

Enter Password:0000

Active Password

Level:none

Global Compressor Setpoints Global setpoints are setpoints that pertain equally to all compressors.

SET COMP SPs GBL (1)

Max # Comp Running=2

Comp Sequence #s

C1=X C2=X

70 OM AGSD3

The maximum compressors running setpoint establishes the maximum number that can run

at any one time. All the compressors would be available and the number specified would

start based on the parameters that determine start sequence. If a unit was ordered with an

extra circuit for standby, this setting could limit the number of compressors that would run

during a warm startup.


Start-Start = XXmin

Stop-Start = XXmin


Pumpdown

Pressure=XX.Xpsi

Time Limit= XXX sec


Light Load Stage

Down Point= XX%slide

Stg Up Delay= XX min

Individual Compressor Setpoints In the following SET COMP#N SPs screens, set the N field to the compressor (circuit)

number desired.

SET COMP#N SPs (1)

Clear Cycle Tmr= no

Comp Size= XXX

Max Slide= XXX.X %

SET COMP#N SPs (2)

Circuit Mode=Enable

Slide Control=auto

Slide Target= XXX.X%

SET COMP#N SPs (3)

EXV Control=Auto

EXV Pos= XXXX

Service Pumpdown=No

SET COMP#N SPs (4)

Slide Pos= XXX.X%

Slide Pos Offset

Min= XX% Max= XX%

SET COMP#N SPs (5)

Pressure Offset(psi)

Evap Cond Oil

XX.X XX.X XX.X

OM AGSD3 71

SET COMP#N SPs (6)

Temp Offset(oF)

Suction Discharge

X.X X.X

Fan Setpoints In the following SET CIRN FAN SPs screens, the N field indicates which circuit is being

viewed.

SET CIRN FAN SPs (1)

Number of fans = X

Fan VFD = ON


Stg On Deadband(°°°°F)

1 2 3 4 5 6

XX XX XX XX XX XX


Stg Off Deadband(°°°°F)

2 3 4 5 6

XX XX XX XX XX


VFD Min speed= XXX%

VFD Max speed= XXX%


Cond Sat Temp Target

Max= XXX.X °°°°F

Min= XXX.X °°°°F

SET FAN SPs (6)

# Fans On At Startup

>75°°°°F >90°°°°F >105°°°°F

X X X

Alarm Setpoints

SET ALARM LIMITS (1)

Low Evap Pressure

Hold=XXXpsi

Unload=XXXpsi

72 OM AGSD3


LowOilDelay= XXX sec

HighOilDpDel=XXX sec


High Disc Temp=XXX°°°°F

HighLift Delay=XXsec


Evap Freeze= XX.X°°°°F

Evap Flow Proof=XXXs LowOATStartTmr=XXsec

Screen Definitions – TEST

TEST UNIT (1)

Alarm Out=Off

Evap Pump 1= Off

Evap Pump 2= Off

TEST UNIT (2)

Comp 1 Enabled=Off

Comp 2 Enabled=Off

Comp 3 Enabled=Off

TEST CIRCUIT (1)

Slide

Load = Off

Unload = Off

TEST CIRCUIT (2)

Liq Line Sol=Off

Economizer=Off

TEST CIRCUIT (3)

EXV Position=XXXX

Fan VFD Spd=XXX.X%

TEST CIRCUIT (4)

Circuit Fans: 1=On

1 2 3/4 5/6 7/8/9

0 0 0 0 0

OM AGSD3 73

Editing Review Editing is be accomplished by pressing the ENTER key until the desired field is selected.

This field is indicated by a blinking cursor under it. The arrow keys then operate as defined

below.

CANCEL (Right).......... Reset the current field to the value it had when editing began.

DEFAULT (Left).......... Set value to original factory setting.

INCREMENT (Up) ...... Increase the value or select the next item in a list.

DECREMENT (Down) Decrease the value or select the previous item in a list.

During edit mode, the display shows a two-character wide menu pane on the right as shown

below.

SET UNIT SPs (X) <D

(data) <C

(data) <+

(data) <-

Additional fields can be edited by pressing the ENTER key until the desired field is

selected. When the last field is selected, pressing the ENTER key switches the display out

of “edit” mode and returns the arrow keys to “scroll” mode.

Alarms

When an alarm occurs, the alarm type, limit value (if any), date, and time are stored in the

active alarm buffer corresponding to that alarm (viewed on the Alarm Active screens) and

also in the alarm history buffer (viewed on the Alarm Log screens). The active alarm

buffers hold a record of the last occurrence of each alarm and whether or not it has been

cleared. The alarm can be cleared by pressing the Edit key. A separate buffer is available

for each alarm (High Cond Pressure, Evaporator Freeze Protect, etc.). The alarm history

buffer holds a chronological account of the last 25 alarms of any type.

74 OM AGSD3

Start-up and Shutdown

NOTICE McQuay Factory Service personnel or factory authorized service agency

must perform initial start-up in order to activate warranty.

! WARNING

Most relays and terminals in the unit control center are powered when S1 is closed and the control circuit disconnect is on. Therefore, do not close S1 until ready for start-up or the unit may start unintentionally.

Seasonal Start-up

1. Double check that the discharge shutoff valve and the optional compressor suction

butterfly valves are open.

2. Check that the manual liquid-line shutoff valves at the outlet of the subcooler coils and

the oil separator oil return line shutoff valves are open.

3. Check the leaving chilled water temperature setpoint on the MicroTech II controller to

be sure it is set at the desired chilled water temperature.

4. Start the auxiliary equipment for the installation by turning on the time clock, and/or

remote on/off switch, and chilled water pump.

5. Check to see that pumpdown switches Q1 and Q2 (and Q3) are in the "Pumpdown and

Stop" (open) position. Throw the S1 switch to the "auto" position.

6. Under the "Control Mode" menu of the keypad, place the unit into the automatic cool

mode.

7. Start the system by moving pumpdown switch Q1 to the "auto" position.

8. Repeat step 7 for Q2 (and Q3).

Temporary Shutdown Move pumpdown switches Q1 and Q2 to the "Pumpdown and Stop" position. After the

compressors have pumped down, turn off the chilled water pump.

! WARNING

Do not turn the unit off using the "Override Stop" switch, without first moving Q1 and Q2 (and Q3) to the "Stop" position, unless it is an emergency, as this will prevent the unit from going through a proper shutdown/pumpdown sequence.

! CAUTION

The unit has a one-time pumpdown operation. When Q1 and Q2 are in the "Pumpdown and Stop" position the unit will pump down once and not run again until the Q1 and Q2 switches are moved to the auto position. If Q1 and Q2 are in the auto position and the load has been satisfied, the unit will go into one-time pumpdown and will remain off until the MicroTech II control senses a call for cooling and starts the unit.

OM AGSD3 75

! WARNING

Water flow to the unit must not be interrupted before the compressors pump down to avoid freeze-up in the evaporator.

! WARNING

If all power to the unit is turned off, the compressor heaters will become inoperable. Once power is resumed to the unit, the compressor and oil separator heaters must be energized a minimum of 12 hours before attempting to start the unit.

Failure to do so can damage the compressors due to excessive accumulation of liquid in the compressor.

Start-up After Temporary Shutdown

1. Insure that the compressor and oil separator heaters have been energized for at least 12

hours prior to starting the unit.

2. Start the chilled water pump.

3. With System switch Q0 in the "on" position, move pumpdown switches Q1 and Q2 to

the "auto" position.

4. Observe the unit operation until the system has stabilized.

Extended (Seasonal) Shutdown 1. Move the Q1 and Q2 (and Q3) switches to the manual pumpdown position.

2. After the compressors have pumped down, turn off the chilled water pump.

3. Turn off all power to the unit and to the chilled water pump.

4. If fluid is left in the evaporator, confirm that the evaporator heaters are operational.

5. Move the emergency stop switch S1 to the "off" position.

6. Close the compressor discharge valve and the optional compressor suction valve (if so

equipped) as well as the liquid line shutoff valves.

7. Tag all opened compressor disconnect switches to warn against start-up before opening

the compressor suction valve and liquid line shutoff valves.

8. If glycol is not used in the system, drain all water from the unit evaporator and chilled

water piping if the unit is to be shutdown during winter and temperatures below -20°F

can be expected. The evaporator is equipped with heaters to help protect it down to

-20°F. Chilled water piping must be protected with field-installed protection. Do not

leave the vessels or piping open to the atmosphere over the shutdown period.

9. Do not apply power to the evaporator heaters if the system is drained of fluids as this

can cause the heaters to burn out.

Start-up After Extended (Seasonal) Shutdown

1. With all electrical disconnects locked and tagged out, check all screw or lug-type

electrical connections to be sure they are tight for good electrical contact.

! DANGER

LOCK AND TAG OUT ALL POWER SOURCES WHEN CHECKING CONNECTIONS. ELECTRICAL SHOCK CAN CAUSE SEVERE PERSONAL INJURY OR DEATH.

76 OM AGSD3

2. Check the voltage of the unit power supply and see that it is within the ±10% tolerance

that is allowed. Voltage unbalance between phases must be within ±3%.

3. See that all auxiliary control equipment is operative and that an adequate cooling load is

available for start-up.

4. Check all compressor flange connections for tightness to avoid refrigerant loss. Always

replace valve seal caps.

5. Make sure system switch Q0 is in the "Stop" position and pumpdown switches Q1 and

Q2 are set to "Pumpdown and Stop", throw the main power and control disconnect

switches to "on." This will energize the crankcase heaters. Wait a minimum of 12 hours

before starting up unit. Turn compressor circuit breakers to "off" position until ready to

start unit.

6. Open the optional compressor suction butterfly as well as the liquid line shutoff valves,

compressor discharge valves.

7. Vent the air from the evaporator water side as well as from the system piping. Open all

water flow valves and start the chilled water pump. Check all piping for leaks and

recheck for air in the system. Verify the correct flow rate by taking the pressure drop

across the evaporator and checking the pressure drop curves in the currewnt version of

the installation manual, IMM AGSC available on www.mcquay.com.

8. The following table gives glycol concentrations required for freeze protection.

Table 17, Freeze Protection Percent Volume Glycol Concentration Required

For Freeze Protection For Burst Protection Temperature

°°°°F (°°°°C) Ethylene Glycol Propylene Glycol Ethylene Glycol Propylene Glycol

20 (6.7) 16 18 11 12

10 (-12.2) 25 29 17 20

0 (-17.8) 33 36 22 24

-10 (-23.3) 39 42 26 28

-20 (-28.9) 44 46 30 30

-30 (-34.4) 48 50 30 33

-40 (-40.0) 52 54 30 35

-50 (-45.6) 56 57 30 35

-60 (-51.1) 60 60 30 35

Notes: 1. These figures are examples only and cannot be appropriate to every situation. Generally, for an extended

margin of protection, select a temperature at least 10°F lower than the expected lowest ambient temperature. Inhibitor levels should be adjusted for solutions less than 25% glycol.

2. Glycol of less than 25% concentration is not recommended because of the potential for bacterial growth and loss of heat transfer efficiency.

OM AGSD3 77

Operating Limits:

Maximum standby ambient temperature, 130°F (55°C)

Maximum operating ambient temperature is 115°F (46°C), or 125°F (52°C) with the addition of

the optional high ambient package

Minimum operating ambient temperature (standard), 35°F (2°C)

Minimum operating ambient temperature (with optional low-ambient control), 0°F (-18°C)

Leaving chilled water temperature, 40°F to 60°F (4.4°C to 15.6°C)

Leaving chilled fluid temperatures (with anti-freeze), 30°F to 60°F (-2°C to 16°C). Unloading is

not permitted with fluid leaving temperatures below 30°F (-1°C).

Operating Delta-T range, 6 degrees F to 16 degrees F (3.3 degrees C to 8.9 degrees C)

Maximum operating inlet fluid temperature, 76°F (24°C)

Maximum non-operating inlet fluid temperature, 100°F (38°C)

78 OM AGSD3

Field Wiring Diagram

Table 18, Typical Field Wiring Diagram

Updated JUL07- Supersedes all previous versions

OM AGSD3 79

FIELD WIRING DIAGRAM continued

80 OM AGSD3

FIELD WIRING DIAGRAM continued

OM AGSD3 81

• (800) 432-1342 • www.mcquay.com OM AGSD3 (8/07)

All McQuay equipment is sold pursuant to McQuay’s Standard Terms and Conditions of Sale and Limited Product Warranty.

This document contains the most current product information as of this printing. For the most up-to-date product information, please go to www.mcquay.com.

Documents

Air-Cooled Screw Compressor Chiller - Daikin Appliedlit.daikinapplied.com/bizlit/literature/lit_ch_ac/IMOM/...Operating Manual OM AGSD3 Group: Chiller Part Number: 331376101 Date: