Customer Property — Contains wiring andservice information. Please retain.

SERVICEFACTS

Notice: Since the manufacturer has a policy of continuous product improvement,it reserves the right to change specification and design without notice. Page G-938-658

IMPORTANT NOTE: This unit isequipped with advanced electroniccontrols which provide convenientservice functions significantly differentfrom conventional units. Refer to yourservice literature carefully whenperforming service or maintenance.

Table 1 - Contents

Models:YCD074C4L0BE, ABE,BBE, CBE, FBE, GBE,YCH074C4L0BE, BBE, FBEYCD074C4H0BE, ABE, BBE, CBE, FBE, GBEYCH074C4H0BE, BBE, FBE

Library Service LiteratureProduct Section Unitary

Product RooftopModel YC✱

Literature Type Service Facts

Sequence 6ADate January 1996File No. SV-UN-RT-YC✱074-SF-6A 1/96

Supersedes New

Table 2 - Product SpecificationsRATED VOLTS / PHASE / HZ 208-230 / 3 / 60 Outdoor Fan - Type PropellerA.R.I. Ratings CFM 4100Cooling (1) No. Used / Dia. 1 / 24Net Capacity (BTUH) 68,000 Type Drive / No. Speeds Direct / 1Indoor Air Flow (CFM) 2500 CFM No. Motors / HP 1 / 0.25System Power (KW) 6.8 Motor Speed R.P.M. 850EER (BTU per Watt) (2) 10.0 Volts / Ph / Hz 208-230 / 1 / 60Heating (3) F.L. Amps / L.R. Amps 2.0 / 5.3Input BTUH (Low Heat) 120,000 INDOOR FAN–Type FC CentrifugalOutput BTUH (Low Heat) 97,000 No. Used / Dia. x Width (In.) 1 / 12.6 x 9.51st Stage Input BTUH (High Heat) 150,000 Drive / Speeds (No.) Belt / 1 Output BTUH (High Heat) 122,000 No. Motors / HP 2nd Stage Input BTUH (7) 205,000 Standard Motor 1 / 1.0 Output BTUH 166,000 Oversize Motor 1 / 2.0Temp. Rise - Min. F (L/H) 25 / 35 Motor Speed R.P.M. 1725Temp. Rise - Max. F (L/H) 55 / 65 Volts / Ph / Hz 208-230 / 3 / 60Type of Gas (4) Natural F.L. Amps / L.R. AmpsPOWER CONNS —V / PH / HZ 208-230 / 3 / 60 Standard Motor 5.9 / 32.2Min. Circuit Ampacity (6) Oversize Motor 8.8 / 53.0Standard/Oversize Motor 35.2 / 38.1 COMBUSTION FAN - Type CentrifugalFuse Size - Max. (Amps) 50 No. Used 1COMPRESSOR Drive/No. of Speeds (L/H) Direct 1/2No. Used 1 Motor HP / RPM (Low) 1/20 / 3350Volts/Ph/HZ 200-230 / 3 / 60 (High) 1/20 / 3000-3500R.L. Amps 21.8 Volts / Ph / Hz 208-230 / 1 / 60L.R. Amps 118.0 F.L. Amps / L.R. Amps 0.4 / 1.4OUTDOOR COIL — TYPE Hi-Performance FILTER FurnishedRows / F.P.I. 2/16 Type ThrowawayFace Area (Sq. Ft.) 11.32 Filters Size 16 x 25 x 1Tube Size (In.) 0.375 Quantity 3INDOOR COIL–Type Hi-Performance REFRIGERANTRows / F.P.I. 3/15 Charge (Lbs. of R-22) (5) 10.0Face Area (Sq. Ft.) 7.88 GAS PIPE SIZE (In.) 1/2Tube Size (In.) 0.375 DIMENSIONS H x W x LRefrigerant Control Short Orifice Crated (In.) 39.0 x 54.5 x 89.7Drain Conn. Size (In.) 3/4" NPT WEIGHT (Approx. Lbs)

Shipping / Net 956 / 767Footnotes:1. Cooling Performance is rated at 95 F ambient, 80 F entering dry bulb, 67 F entering wet bulb and nominal cfm listed. ARI capacity is net and includes the effect of fan motor heat. Rated in accordance with ARI Standard 210.2. Rated at ARI conditions and in accordance with DOE test procedures.3. Heating performance limit settings and rating data were established and approved under laboratorytest conditions using American National Standards Institute standards. Ratings shown are for elevations up to 2000 feet.4. Convertible to LP gas with orifice change.5. Refrigerant charge shown is a nominal value; for a more precise value see the unit nameplate. 6. Values do not include power exhaust accessory.7. Applies to High Heat models only.

Failure to DISCONNECTPOWER before servicingcould lead to severe personalinjury or death.

▲ ▲ ▲ ▲ ▲ WARNING: HAZARDOUS VOLTAGE-DISCONNECT POWER BEFORE SERVICING!SAFETY NOTICEThis information is intended for use by individualspossessing adequate backgrounds of electrical andmechanical experience. Any attempt to repair a central airconditioning product may result in personal injury and/or prop-erty damage. The manufacturer of seller cannot be respon-sible for the interpretation of this information, nor can it as-sume any liability in connection with its use.

RE-CONNECTALL GROUNDING DEVICESAll parts of this product capable of conductingelectrical current are grounded. If grounding wires,screws, straps, clips, nuts or washers used tocomplete a path to ground are removed forservice, they must be returned to their originalposition and properly fastened.

YC✱✱✱✱✱074-SF-6A

Packaged Cooling/Gas Heat6 Tons-Downflow & HorizontalMicro-Electronic Controls

PageContents .......................................... 1Table 2 - Product Specifications ...... 1Table 3 - Optional Equipment .......... 2Sequence of Operation ................... 2Unit Start-Up ................................... 2Cooling Operation/MechanicalCompressor Cycle .......................... 2Cooling Operation/Economizer Cycle ........................... 2Continuous Fan Operation .............. 3Heating Operation/Gas Heat ........... 3Ignition Control Module Diagnostic . 3Operating Pressures Curves ........... 5Superheat Charging Chart .............. 5Connection Diagram (Low Heat) ..... 6Connection Diagram (High Heat) .... 8Power Schematic .......................... 10Control Schematic ......................... 12Refrigerant Circuit Diagram .......... 14

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Table 3 - Optional Equipment

Manual Change-over T’stat - Single Stage . ASYSTAT661BAuto Change-over T’stat - 2 stage .............. ASYSTAT663BProgrammable T’stat ................................... ASYSTAT666AStand Alone Unoccupied Timer ................... BAYCLCK001AConventional T’stat Interface - Field Installed ........................... BAYCTHI001CRoof Curb .................................................... BAYCURB022BClogged Filter Switch .................................. BAYDFPS001AFan Failure Switch ...................................... BAYDFPS002AI/O Expansion Board ................................... BAYDIAG001AManual Outside Air Damper ........................ BAYDMPR029BPower Fresh Air .......................................... BAYDMPR045BEconomizers - (Downflow) .......................... BAYECON068B Horizontal ................................. BAYECON070B Without Controls for YCD ......... BAYECON072BReference Enthalpy Control ........................ BAYENTH003AComparative Enthalpy Control .................... BAYENTH004AHigh Temperature Sensor ........................... BAYFRST001ACoil Guard ................................................... BAYGARD023AHigh Static Motor ........................................ BAYHSMT049ATCI Accessory ............................................. BAYICSI001BHorizontal Insulation Kit .............................. BAYINSL101AQuick Start Kit ............................................. BAYKSKT007BPropane Conversion Kit .............................. BAYLPKT023BSensor Mounting Plate ................................ BAYMTPL002APower Exhaust for YCD .............................. BAYPWRX013AZone Sensor - Single Stage Manual T’stat . BAYSENS006BZone Sensor - 2 Stage Auto T’stat .............. BAYSENS008BZone Sensor w/LED - 2 Stage Auto T’stat .. BAYSENS010BZone Sensor w/Button ................................ BAYSENS013BZone Sensor w/Button and Setpoint ........... BAYSENS014BTemperature Sensor ................................... BAYSENS016ARemote Sensor for Auto Change-over T’stat . BAYSENS017BZone Sensor - Programmable ..................... BAYSENS019ADigital Dual Man/Auto ................................. BAYSENS022AService Tester - Selective Resistance ......... BAYSERV001ARemote Sensor for Programmable T’stat .... BAYSTAT021Remote Rheostat ........................................ BAYSTAT023

Sequence of Operation

These units are equipped with an electronic control board“Unit Control Processor (UCP)” which is the brain of theunit control system. This board contains powerful controllogic information that manages the functioning of the unit andsystem.

Note: The time delays mentioned below are controlledby the UCP, and are present to increase systemreliability. They protect the compressor and maximizeefficiency of unit performance.

1)Unit Start-UpEach time power is applied to the system, the UCPperforms internal self-diagnostic checks. It determinesthe system configuration (including installed options), andprepares for control of this configuration. It also checksitself for proper internal functioning. Within one second ofstart-up, the UCP system indicator (a red light on the UCPboard) glows if programming is intact and functional.

On units with the optional economizer, the damper(s) isdriven open for 15-20 seconds, and then closed forapproximately 90 seconds. This assures proper dampercalibration.

2)Cooling Operation/MechanicalCompressor Cycle(For cooling without economizer operation)

Note: The compressor is controlled to a minimum runtime of three minutes, and once shut off will not startagain for three minutes.

Cooling Sequence —When mechanical cooling isrequired, the UCP energizes the Compressor Contactor(CC1) coil. When the CC1 contacts close, theCompressor CPR1 and Outdoor Fan Motor (ODM)start. CPR1 cycles on and off as required by coolingdemands, but within the time minimums mentionedabove.

Defrost Cycle in Cooling ModeDuring periods of low outdoor air temperature, the UCPperforms an evaporator defrost cycle. This cycle isperformed at temperatures below 55° F after each 10minutes of accumulated compressor run time. During thedefrost cycle the compressor(s) is turned off and thesupply fan stays energized. After completion of thedefrost cycle, which lasts approximately three minutes,the compressor is allowed to operate as required.

Indoor Fan OperationIf the indoor fan is set to “AUTO” , the UCP energizes theIndoor Fan Contactor (F) coil approximately one secondafter energizing the compressor contactor. The IndoorFan Motor (IDM) starts when contacts of F close. Whenthe cooling cycle is complete and CC1 is de-energized,the UCP keeps the F coil energized for 60 seconds ofadditional IDM operation to enhance unit efficiency.

3)Cooling Operation/Economizer CycleThe economizer option allows cooling with outdoor airwhen outdoor ambient is below 60(±2)° F. (This setting isfield adjustable to 55 or 65° F). This air is drawn into theunit through modulating dampers. When cooling isrequired and economizing is possible, the UCP signalsthe Unitary Economizer Module (UEM) to open/close theventilation damper(s) by energizing the EconomizerActuator (ECA). The UCP tries to cool the space toslightly below the cooling set-point. If the Supply AirSensor (SAS) senses that supply air is below 50° F, thedampers modulate closed until supply air temperaturerises, or until dampers close to their minimum position.

If a power exhaust accessory is present, the powerexhaust fan motor is energized whenever the economizerdamper is at a position greater than 25% of the actuatorstroke.

During simultaneous economizing and mechanicalcompressor cooling, the UCP continues to modulate theECA to keep the supply air temperature in the 50-55° Frange. When economizing is not possible, dampers go tominimum position.

Settings - The economizer is opened to minimumventilation position by the UCP every time F isenergized. The amount of ventilation air required is setby adjusting the minimum position potentiometer locatedon the Unitary Economizer Module (UEM).

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4)Continuous Fan OperationIf the indoor fan switch is set to “ON” , the UCP keeps theF coil energized for continuous fan operation. On unitswith an optional economizer, the UCP also causes theEconomizer Actuator (ECA) to move to its properoperating position at minimum position or greater.

5) Heating Operation/Gas HeatWhen the space temperature falls below the heating set-point, the UCP initiates a heating cycle by energizing therelay (K5) coil, the heat relay (H) coil, the Ignition ControlModule (IGN)., and relay (S) coil when present. The Hcontacts close to energize the Combustion Fan Motor(CFM). On units with 2-speed switching fans (3 & 4 tonhigh heat models), the K5 (for 208/230V units) or S relay(for 460/575V units) also energize the high speedwindings of the Indoor Motor (IDM). On two stage units,the K5 contacts close to energize the high speedwindings of CFM. (After a 60 second delay, K5 is de-energized to revert the CFM to its low speed windings.)

The IGN starts the ignition process by preheating the hotsurface Ignition Probe (IP) for 30 seconds. After preheatof the IP, the Gas Valve (GV) is energized up to 7seconds to ignite the burner. When the gas lights, the IPis de-energized and then functions as a flame sensor.

If the burner fails to ignite, the ignition module will attempttwo retries. At the start of each ignition retry, the greenLED will flash and the red LED will flash for five secondsbefore locking out. An IGN lockout can be reset by;

1. Opening and closing the main power disconnectswitch,

2. By switching the “Mode” switch on the zone sensor to“OFF” and then to the desired position.

3. Allowing the ignition control module to resetautomatically after one hour. Refer to the “Ignition ControlDiagnostics” section for the LED diagnostic diffinitions.

If the fan is set to “AUTO” , the UCP energizes the FanContactor (F) 30 seconds after initiation of the heatcycle. When the F contacts close, the IDM starts. Forunits with automatic 2-speed fan switching, the fan runs inhigh speed.

For 2-stage Gas Heat units onlyIf the space temperature remains below the heating set-point with stage 1 heat operating, the UCP energizes theK5 coil. This activates the high speed windings of CFMsupplying stage 2 heat capacity.

When the space temperature rises above the heating set-point, the UCP de-energizes K5, H, and IGN, and S ifpresent, turning off the heat functions. The F coil remainsenergized for 90 seconds after which it is de-energized,provided the fan mode is AUTO. If the fan mode is “ON”and automatic 2-speed fan switching is present, the fanreturns to low speed.

To reset an IGN lockout, power must be removed fromIGN by switching the unit mode on the zone sensor to“OFF” and then to the desired position.

Limit ControlsHigh Limit (TCO1) and Fan Fail Limit (TCO2) protectagainst overheating if the IDM fails to operate. (TCO2)will signal the UCP that a failure has occurred. The UCPwill de-energize K5, H, and IGN, and energize the Fcoil. The UCP also signals the heat failure by flashing the“HEAT” LED on the zone sensor.

TCO1 is located in the bottom right corner of the gasvalve/burner compartment. This automatic reset controlprotects against abnormally high leaving air temperature.

TCO2 is located in the upper middle section of the indoorfan panel. This automatic reset control protects againstabnormally high heat build up, which could be caused byextended cycling of TCO1, or failure of the IDM tooperate.

Ignition Control Module Diagnostic

There are two LED’s located on the Ignition Control Module.The Table below list the diagnostics and the status of theLED’s during the various operating states.

LED StatusDiagnostics Green LED Red LED1. Powered with no call for heat Off Off2. Call for heat - no fault detected Flashing (1) Off

3. No Flame signal on try for ignition Off Flashing (2) or flame signal established and lost prior to a lockout condition.

4. Gas Valve miswired or flame Continuous Flashing (1) signal present at a call for heat5. Internal Fault - anytime. Off Continuous

Notes:1. Flash at a 50% duty cycle.2. At the start of each retry for ignition the red LED will flash for five seconds along with the green LED

Table 4Static Pressure Drops ThroughEconomizers (Inches Water Column)

CFM Full Return* Full Outside1600 0.01 0.071700 0.01 0.082000 0.01 0.102100 0.01 0.102400 0.02 0.122500 0.02 0.133000 0.03 0.153600 0.03 0.20

*For Power Fresh Air, “Full Return” is zero.

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Table 5Evaporator Fan Performance

Fan Speed (RPM)Motor

Sheave Standard High Static Low StaticPosition Motor & Sheave Motor & Drive Sheave *

5 Turns Open 735 923 5254 Turns Open 805 992 5753 Turns Open** 875 1060 6252 Turns Open 945 1129 6751 Turns Open 1015 1197 725Closed 1085 1265 775 * Field Supplied** Factory setting is 3 turns open.

Table 6Evaporator Fan Performance

External Static Pressure (Inches of Water) 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.25 1.50

CFM RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP1 HP Standard Motor & Field Supplied

Low Static Drive (1)2000 615 0.37 663 0.41 710 0.45 756 0.49 799 0.52 843 0.55 884 0.58 924 0.60 965 0.62 1006 0.62 — — — —

YCD Low & 2250 681 0.52 723 0.56 766 0.61 807 0.65 848 0.69 886 0.73 925 0.76 964 0.79 1000 0.82 1035 0.84 1126 0.90 1209 0.92High Heat/ 2500 748 0.69 785 0.74 824 0.79 862 0.84 899 0.89 936 0.93 971 0.98 1005 1.02 1041 1.06 1075 1.09 1154 1.16 1237 1.22YCH Low 2750 816 0.91 849 0.96 884 1.02 920 1.08 954 1.13 988 1.18 1021 1.23 1053 1.28 1084 1.32 1116 1.37 1195 1.46 1266 1.54

Heat 3000 884 1.17 915 1.23 946 1.29 979 1.35 1011 1.41 1042 1.47 1073 1.52 1104 1.57 1134 1.63 1163 1.68 1235 1.80 — —1 HP Standard Motor & Sheaves 2 HP Oversized Motor & Sheaves

External Static Pressure (Inches of Water) 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.25 1.50

CFM RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP RPM BHP2 HP Standard Motor & Field Supplied

Low Static Drive (1) 1 HP Standard Motor & Sheaves2000 680 0.45 738 0.50 794 0.55 846 0.63 894 0.63 947 0.67 1003 0.70 1055 0.72 — — — — — — — —

YCH 2250 751 0.63 804 0.69 853 0.74 903 0.80 949 0.84 992 0.88 1037 0.92 1086 0.97 1135 1.00 1181 1.03 — — — —High Heat 2500 824 0.84 872 0.91 917 0.97 961 1.03 1006 1.09 1047 1.14 1085 1.19 1126 1.24 1167 1.28 1212 1.33 — — — —

2750 899 1.11 940 1.18 984 1.25 1023 1.32 1064 1.39 1105 1.45 1142 1.51 1178 1.56 1214 1.61 1250 1.66 — — — —3000 974 1.42 1010 1.50 1051 1.58 1089 1.65 1124 1.73 1162 1.80 1200 1.88 1235 1.94 1268 1.99 — — — — — —

2 HP Oversized Motor & Sheaves Notes:Motor efficiency: 72%Data includes pressure Drop Due to Wet Coils and Filters.1. Field supplied Browning fan sheave AL74 and Belt A48 required.

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Operating Pressures Curves

To Check Operating Pressures1. Start the unit and allow the pressures to stabilize. 5. Plot the outdoor dry bulb and the indoor DB/WB temperature 2. Measure the indoor DB/WB temperature entering the indoor coil. onto the chart.3. Measure the outdoor air dry bulb temperature 6. At the point of intersection, read down for the suction 4. Take discharge and suction pressure readings. pressure and to the left for the discharge pressure.

COOLING CYCLE PRESSURE CURVE(Based on 2500 CFM Indoor Airflow)

FULL LOAD

150

200

250

300

350

400

450

60 65 70 75 80 85 90 95 100 105 110

SUCTION PRESSURE, PSIG

DIS

CH

AR

GE

PR

ES

SU

RE

, PS

IG 115 F OD Ambient

105 F OD Ambient

95 F OD Ambient

85 F OD Ambient

75 F OD Ambient

65 F OD Ambient

55 F OD Ambient

68/5

7 F

ID D

B/W

B

74/6

2 F

ID D

B/W

B

80/6

7 F

ID D

B/W

B

86/7

2 F

IN D

B/W

B

Superheat Charging Chart

1) REFRIGERANT CHARGE - ADD if the superheat is more than 5O above curve value.- REDUCE if the superheat is more than 5O below curve value.- OK if the superheat is within 5O of curve value.

2) Do not add refrigerant if the superheat is less than 5O F3) Curves are based on 400 CFM/Ton Indoor Airflow @ 50% R.H.4) system must be running at stablized conditions before measuring superheat.

Charts Based on Indoor Airflow of 400 CFM / Ton

0

10

20

30

40

50 60 70 80 90 100 110 120

OUTDOOR AMBIENT TEMPERATURE, DB (O F)

CO

MP

RE

SS

OR

SU

PE

RH

EA

T, (

O F

)

To Determine Required Superheat -A) Plot the Outdoor Temp onto the bottom axis of the curve.B) Move vertically to the appropreiate indoor DB/WB temp. (or interpolated temp)C) At the point of intersection, (OD & ID) read horizontally to the left for the required superheat.

68 / 57 ID DB / WB O F 74 / 62 ID DB / WB O F 80 / 67 ID DB / WB O F

86 / 72 ID DB / WB O F

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Connection Diagram (Low Heat)2307-5592

7

8

Connection Diagram (High Heat)2307-5594

9

10

Pow

er Schem

atic2307-5615

11

12

Control S

chematic

2307-5583

13

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Table 7Gas Heating Data

Model: YC074C LOW HEAT HIGH HEATHeating Input Rate – BTUH 120,000 205,000Minimum Gas Supply Pressure Natural 3.5” W.C.(Entering Gas Valve) LP 8.0” W.C.Gas Pressure Leaving Gas Valve-Manifold Pressure(See Note 1) -0.2” W.C.Combustion Blower Suction High Fire -2.1 to -3.1” W.C.(With Gas Valve Closed) Low Fire N/A -0.8 to -1.2” W.C.Minimum Flame Sensing Current 1.0 Microamps D.C.(See Note 2)Normal Sensing Current Range 1 to 8.0 Microamps D.C.Flue Gas Temperature Rise Above Ambient @ Deg. F 350 to 525° 350 to 475°Flue Gas Content - %CO2 Natural 8.3 to 9.5 8.0 to 9.0

LP 10 to 11 9.5 to 10.5Minimum Supply Air Temperature AcrossHeat Exchanger 40° FNotes:1. This Unit has a negative regulation gas valve. Never adjust gas manifold pressure to a positive pressure. 2. A voltage reading across pens (V+) & (V-) is equatable to the flame sensing current. One volt equals one micro amp.

Refrigerant Circuit Diagram

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© American Standard Inc. 1996 Technical Literature Printed in USA