Chapter - 13 Control Strategies

႔ Chapter-13 Control Strategies

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Chapter - 13 Control Strategies

၁၃.၁ Starting Sequence and Shutdown Sequece of Chilled Water Plant chiller ၊ c um ၊ co s

water pump cooling tower Chilled water plant

၁၃-၁ Schematic diagram of chilled water plant

HVAC Controls and Building Automation Systems ႔

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၁၃.၁.၁ Starting Sequence of Chilled Water Plant Centralized chilled configuration

chilled water plant configuration (၁) Primary only configuration (၂) Primary and secondary configuration (၃) Variable primary configuration ႔

Water Cooled Chilled Water Plant Water cooled chiller plant sequencing A coo c

coo o condenser um ,

Primary only co u o m c um S co c um m s co co u o m c um secondary chille um coo c co s um

၁၃-၂ Water cooled chilled water system schematic

u m ၊ oc oc equipment and humam safety c c ၊ m c c - wat coo c c um co s um coo c i oc

oc oc software interlock H inte oc control p oc o oc DDC controller program


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c operation u m ႔ “Starting Sequence”

(၁) Air Handling o Air Handling Unit/Fan Coil Unit (AHU/FCU) AH c co o (fully closed position o 553:2009 13 AH co o

AH c co o c um ႔ AH AH chille co o i oc

(၂) AH p m c um primary c um so o valve um isolation valve oc m c um so o valve primary chil um

c p m c um - c ၃ primary chilled water pump ၃ um ႔ fu o co o s ႔

centralized chiller plant s co c um co c um s co c um so o valve um isolation valve oc ႔ seco c um

(၃) oo o solation valve oo o isolation valve oc Coo o Coo o so o valve condenser wa um

(၄) o s um so o valve ႔ co s um Pum isolation valve i oc chiller co s um um ႔ full load conditio s ႔

(၅) C C chilled wa co s ႔ o o s c ႔ differentical pressuer switch Chiller chilled water flow s c condenser water flow switch ႔ oc

u m (time delay) u m operator m u sc u Buildig Automation Sysetm (BAS) cotrolle


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starting s u c chiller plant ႔ c c oom ႔ (consultant)၊ building owner)၊ ႔ engineering team) ႔ chiller s s u c “Fine Tuning”

Air H o cooling tower Primary pum secondary pum chiller plant um

၁၃.၁.၂ Shutdown Sequece of Chiller Plant Room u o s u c s s u c

၂၄ c oom s u o

၁၃.၂ Typical chiller sequencing strategies Chiller sequencing cooling load chiller

Cooling load ၊ chilled water temperature chiller motor loading ႔ chiller sequencing

၁၃.၂.၁ Chiller Sequencing for Systems with only Primary Pumping Chilled Water Leaving Temperature Chiller Sequencing

၁၃-၃ Chilled water temperature s u c

Chilled water temperature chiller sequenceing (၁၃-၃) T1 ၊ T2 ႔ T3 chilled water leaving temperature set point chiller cooling capcity

shutdown) c s u o timing) c ၄၅ ႔ s u o ႔ early s u o (energy saving) s u o coo o cond s um s u o um ၁၅ s u o AH ၅ shutdown) c ႔ s u o c c cu o coo ss


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cooling load ႔ chiller

၁၃.၂.၂ Chiller Sequencing for Systems with only Primary Pumping Cooling Load and Chilled Water Temperature Chiller Sequencing

၁၃-၄ Cooling load chilled water temperature c s u c

Cooling load chilled water temperature chiller sequencing (၁၃-၄) chilled water temperature difference (T2 – T1) chilled water flow rate cooling load

(AND) ႔

chiller ( ) T1 chilled water temperature set point

AND / OR ( )

cooling load chiller cooling capacity A ၊

chiller ( ) T1 chilled water temperature set point

AND / OR ( )

cooling load chiller cooling capacity Cooling load chiller sequencing

႔ chiller (off-design operating conditions) design capacity capacity - condenser water supply temperature ႔ chilled water temperature chiller rated capacity capacity


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၁၃.၂.၃ Cooling load ၊ Chilled Water Temperature Motor Loading Cooling load ၊ Chilled Water Temperature Motor Loading Chiller Sequencing

၁၃-၅ Chiller sequencing using cooling load ၊ chilled water temperature and motor loading

(၁၃-၅) primary only chiller water system chiller sequencing Recommended strategy

႔ (standby) chiller (cut in) (၁) 1 chiller (leaving chilled water temperature)

set point ၊

(၂) cooling load chiller capacity ၊

(၃) ampere full load ampere

(AND) standby chiller ႔ (၅) (AND) (standby) chiller

chiller (cut out) cut out condition

(၁) 1 chiller (leaving chilled water temperature) set point ၊

(၂) Cooling load operating chiller capacity ၊

(၃) Chiller motor ampere full load ampere

chiller chiller ႔

ဤ chiller sequencing off-design operating ၊ design operating c loading


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၁၃-၆ Chiller sequencing for primary-secondary systems using decoupler flow and chilled

water temperature

Primary-secondary pumping s s m primary oo secondary oo c um oo Primary oo c oo Chilled water secondary oo AH Primary oo secondary oo hydraulically decoupled

၁၃-၆) decoupler pipe bi-directional flow meter Flow meter ၊ R u s supply side ႔ secondary loop c primary loop c ႔ c ႔ T1 ၊ 2 ႔ T3 chilled water leaving t m u s o c coo c c coo o c

Decoupler su s return side ႔ chilled water chiller flow ၁ c ဤ cooling load ႔ chiller o sequenceing

၁၃.၂.၄ Strategy for Chiller Sequencing for Systems with Primary-Secondary Pumping Primary-secondary pumping comm

s (၁၃-၇) primary chilled water loop flow rate secondary chilled water loop flow rate chilled water flow meter Flow rate decoupler pipe

Primary-S co s s m cou o c s u c (၁၃-၃) u s su s ႔ s co oo c o primary oo c o ႔ s c


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Chilled water leaving temperature (T1) s o standby) c

၁၃-၇ Chiller sequencing for primary-secondary systems using individual flow meters and

chilled water temperature D cou su s c return side ႔

၊ c ႔ c ၁ ) c chiller (shutdown)

၁၃.၂.၅ Strategy for Chiller Sequencing for Variable Flow Systems (၁၃-၄) variable flow system Flow Meter (FM) ၊ chilled water

return temperature chilled water supply temperature (TS) sensors ႔ coo o coo o c s u c

၁၃-၈( ) Variable primary flow system

chiller ႔ c mo o um -2 ssu s so


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co o -2 um AH co ssu

-1 ssu s so motorized by-p ss co o C m mum o -1 differenti ssu s so s - o ႔ co o oo ss c ႔ c ss

ss chilled water -2 ssu s so ႔ um co o s C m mum o minimum) um 0 9 m s 3 m s m c cu o m

၁၃.၃ Chilled Water Plant Sequencing and Automation ( ) o c chilled water plant sequencing automation

c s s u (၁၃-၈ ) water cooled centrifugal chiller ၃ ၊ chilled water pump (၃ ၊ condenser water pump (၃ cooling tower (၃ ႔ muti-c s s u c co o o m Chiller (CH-1)၊ chilled water pump (CWP-1)၊ condenser water pump(CDWP-1)၊ cooling tower (CT-1) ႔ chiller system (၁

Air conditioning system (၁) AHU (start) (၂) Chiller system (start) ( ) Cooling tower (start) ( ) Condenser water pump (start) ( ) Chilled water pump (start) (၃) ႔ chiller

Chiller System Mode of Operation Supervisory panel console operation mode (၃) (၁) Off Mode : Chilled water plant (၂) BAS Mode : DDC controller program mode

(၃) Local Mode : Supervisory panel o o ၊ mode

Motor Control Center (MCC) panel operation mode (၃) (၁) Off Mode : Chilled water plant (၂) Remote Mode : Supervisory panel control (၃) Local Mode : Chiller system equipment local panel ၊

mode


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၁၃-၈

( ) C

hille

d w

ater

pla

nt g

raph

ic


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u u m s u c u m c o u u m s u c u m u ou s o m

(၁) Cooling Tower Operation and Controls Cooling tower o o c c

o cooling to ၊ cooling to

ဤ program ႔ day mode) s cooling to s coo o u s coo o s (night mode) c coo o

( ) Start-up sequence (၁) Isolation valve o comm (၂) Valve (open) s us cooling tower fan (start) (၃) (on) status fan operation control

(၄) cooling tower fan

(mo o

( ) Stop Sequence (၁) Tower fan (stop) comm (၂) Fan (off) status isolation valve

(close) ႔ (၃) Valve (closed s us

( ) Cooling Tower Fan VSD Controls Cooling tower fan VSD speed) control

- Condenser water supply temperature VSD speed control - Ambient Wet Bulb temperature(°C)+2.5° VSD speed control (၁) Cooling tower (condenser water supply temperature)

cooling tower fan VSD control ( ) (၂) Condenser water supply temperature ႔ cooling tower leaving temperature

set point VSD speed control (၃) Temperature set point VSD speed (increase)

(၄) Temperature set point VSD speed (decrease)


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(ဃ) Cooling Tower Fail Flag Cooling tower system ႔ f - (activate) alarm condition ႔

(၁) Fan (၂) (fail) ႔

(၂) Isolation valve “open” command (fail to open)

(၃) Isolation valve “close” command (failed to closed)

- (activate) cooling tower enable

s m “o ” command chiller system “o ” comm

(၁) Master command enable (၂) cooling tower (status is ON) (၃) Chiller fail-flag (not activated) ႔ equipment trip

႔ equipment oc mo (၄) Chiller sequence staging control program

Chilled Water System Cooling Load Calculation Cooling load BTU meter

(၁) Chiller cooling capacity chiller BTU meter

(၂) Main chilled water header BTU meter Chilled water system cooling capacity chilled water main header BTU meter

(၃) BTU meter cooling load (reading) MODBUS commu c o BAS

(၄) cooling load (formula)

( ) [ ( ) ( )]

( ) ( ) ( )

( ) [ )] ( )

Chiller power meter (power comsumption)

႔ efficiency (kW/RT)

( ) ( ) [ ]

( )[ ]


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Every Initial Startup of the Master Chiller System Command Chiller chiller

“initial startup” 650 RT chiller

Chiller chiller (၂ ) ႔ (delay 20 minutes)

Staging Controls for Chiller System chiller chiller Chilled water supply temperature 9.5°C (chilled water supply temperature

> 9.5°C) OR Cooling load chiller capacity 100%

chiller ၁ cou o s m ၊ c

chi ၃ cou o ၃ c s u o c

Staging Controls for Chiller System chiller chiller (shutdown) Chilled water differential pressure 5°C (chilled water differential pressure

< 5°C) AND Cooling load chiller capacity 45%

(AND) chiller ၁ cou o s m ၊ c

၃ cou o ၃ c s u o c

Alarm Conditions for Chiller System Fail-Flag chiller system fail-f

(၁) Chiller ၊ chilled water pump ၊ condenser water pump ၊ cooling tower (failed to run)

(၂) Chiller ၊ chilled water pump ၊ condenser water pump ၊ cooling tower ႔ local mode ႔


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Failure Changeover (၁) chiller system fail-flag (activate)

chiller ႔ (stop sequence) (initiate) (၂) chiller system chiller system

Startup Sequence Chiller system enable command start-up sequence

Chiller cooling load BTU meter chiller cooling load BTU meter header

(၁) Condenser Water Pump(CWP) (start) comm

(၂) Condenser Water Pump(CWP) ON status Chilled Water Pump (CHWP) (start) comm

(၃) Chilled Water Pump (CHWP) ON status (၅) count down

(၄) Chiller (start) comm

Chiller system (၃ ) count down (၃ ) chiller ႔

Shutdown/Stop Sequence Chiller system s comm shutdown sequence

( ) Chiller (stop) comm

( ) Chiller OFF s us (၅) count down

( ) (၅) CHW pump (stop) comm

(ဃ) H us ( .၅) count down

( ) ( .၅) CWP (stop) comm

( ) CHWP ႔ OFF status

Chiller system ႔ “prohibited command” activate Prohibited command chiller (၁၅)

Condenser Water Pump VSD Control (၁) flow meter flow rate set point VSD

speed control (၂) (flow rate) set point VSD speed (increase) (၃) (flow rate) set point VSD speed (decrease)

Chilled Water Pump VSD Control (၁) flowmeter flow rate set point VSD

speed control


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(၂) (flow rate) set point VSD speed (increase) (၃) (flow rate) set point VSD speed (decrease)

Cooling Tower Fan VSD Control (၁) Condenser water supply temperature set point ( ambient temperature

sensor Web Bult +2.5°C) cooling tower Fan VSD speed control

(၂) Condenser water supply temperature set point VSD speed (decrease)

(၃) Condenser water supply temperature set point VSD speed (increase)

By-Pass Valve Controls (၁) System operating pressure differential pressure sensor main chilled

water header (၂) (pressure) set point by-pass valve modulate

By-pass valve main header (pressure

Controlling of Chiller Set point via High-level interface Chilled water supply temperature set point ၁၃-၈( ) (outdoor air temperature) High-level interface reset

၁၃-၈( ) Chilled water temperature set point strategy

၁၃.၄ Chillerd Water Plant Optimization Strategies ၁၃.၄.၁ Fixed start/stop Vs Optimal start/stop

Fixed start/stop chiller plant room ၏ ႔ ႔ (fixed) ၊ ႔

Optimal start/stop (outdoor temperature) chiller plant ၊ (၁) ႔ ႔ (outdoor temperature) chiller plant ၍ ရပနား (shutdown) ၊ ၊ ၍လညး optimal start/stop timing

၍ ေမာငးရမညက ou oo m u ႔ s u o ou oo m u u ၍ ခန႔မနးႏငသည။ အေဆာကအဥ ႀကးမား thermal mass oo m u


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၁၃.၄.၂ Leaving Chilled Water Set point with Constant Primary Flow co s s c

leaving chilled water set point s L c temperature 1°F(0.6°C) c energy consumption)၏ 1 ႔ 2 s Building autom o A H Fan Coil Unit ႔၏ c co o os o ၍ s

၁၃.၄.၃ s Chilled water set point reset

( ) Resetting Chilled Water Set point Based on Outdoor Air Temperature (outdoor temperature building heat load

(outdoor temperature) chilled water set point

၏ ဒဇငး အျမငဆး ျပငပအပခန(outdoor temperature) 35°C 38°C Dry Bulb cooling load 35°C ၍ တြကထားသည။ အကယ၍ ျပငပအပခန(outdoor temperature) 26.7°C chilled water set point chilled water set point reset (၁၃-၈)

Chilled Water Temperature (°C) Outdoor Temperature (°C) 6.7°C(44°F) (Standard) 35°C(95°F) or higher 8.9°C(48°F) or higher 26.7°C(80°F) or below

( ) Resetting the Chilled Water Set point Based on Total Building Load ၏ o o coo

o ၍ c s oo o c m u ၏ o o ၏ o o ၏ o o chilled water set point

( ) Resetting the Chilled Water Set point Based on Summer/ Winter Mode or Time Schedule ၊ ၊ ၍ chiller water set point ၏

အနမဆး chilled water set point ၏ အနမဆး set point 2 ျပငပအပခန(outdoor temperature) set point

၍လညး set point reset Shopping center (၁ ) chiller shutdown ႔ chilled water set point 8.5°C Shopping center customer ၊ shopping center ႔ ဤ ႔ cooling load ႔ (predict) chiller မ unload chilled water set point chiller unload


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၁၃-၉ Control strategy for optimizing variable speed chilled water pumps

(ဃ) Resetting the Chilled Water Set Point Based on AHUs and FCUs Control Valve Position Building Automation System (BAS)၏ AHU FCU ႔ ၏

valve position Control valve ႔ ၏ position (%) valve ၏ position (%) valve Valve ၏ position (%) 90% chilled water set point Valve ၏ position 90% air side(demand side)၌ cooling load

Valve ၏ position 90% 70% supply side(chiller side) demand side(air side) ၏ cooling load (match) ၸ chiller water temperature set point set point ၊ Valve ၏ position 70% chilled water set point chilled water set point set point ႔ set point ႔ (၁၃-၉) chilled water reset strategy ၏ control logic maximum set point minimum set point

Valve ၏ position POSMAX ၍ (၃)

POSMAX 90% minimum set point ၊ chilled water set point minimum set point ႔ 0.2°C

chilled water stepoint minimum set point ႔ (valve ၏ position 90 POSMAX 70% 90% chilled water set point

POSMAX 70% maximum set point ၊ chilled water set point 0.2°C


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chilled water set point maximum set point ႔ (valve ၏ position POSMAX 70%

၁၃-၁ Pressure–enthalpy diagram showing effect of increasing chilled water temperature

(၁၃-၁ ) P-h diagram vapour compression cycle Compressor evaporator pressure refrigerant condenser pressure compress

Chiller lift chiller compressor ၏ mou o o o R22 refrigerant chiller compressor ၏ lift entering chilled water temperature condenser water leaving temperature

- R-22 refrigerant 7°C (corresponding) Evaporator pressure 21 8°C (corresponding) Evaporator pressure 1 29.0 (corresponding) Condenser pressure 11 2

Chiller set point 7°C 8°C ႔ compressor 621 kPa (7°C) 1162 kPa (29°C) ႔ compress 641 kPa(8°C) 1162 kPa(29°C) ႔ compress ႔ 20kPa (power consumption)

( ) Resetting the Chilled Water Set point Based on Return Temperature AH c ၏ s H su m u H u

m u 12 2 H u m u 12 10 ႔ H su m u H u m u ဒ 12 ႔ H u m u ဒ 12 10 ႔ coo o H o co s

o s s m coo o CHW flow H u m u ႔ ဤ ႔ s co s o s s m

o H um s s m H su m u c c c H o um ၍


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႔ energy) s c um ၏ co sum o

၁၃-၁၁ Effect of chilled water temperature on chiller and pump efficiency.

၁၃-၁၁ H su m u chiller ၏ efficiency um c c mum o o c um o c c o mum o o c um ႔၏ o m c c c s c ၍

၁၃.၅ Boiler Controls (boiler) (combustion rate)

u o o Boiler load (optimum fuel to air ratio) feedwater level control system

၁၃-၁၂ Typical arrangement of boiler plant used for space heating

႔ (steam pressure) (boiler) control Steam usage (load) ၊ ႔ (steam pressure) control Steam usage (load) steam pressure ႔ ႔ (steam pressure) (fuel) (flow) (combustion rate) control


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fuel flow rate) co o air-to-fuel ratio) co o c s s m u s ႔ com os o air-to-fuel ratio) con o

o co o s s m (boiler) m mum m mum s um co o

၁၃-၁၃ Typical controls for boilers

၁၃-၁၄ Main inflows and outflows for a

typical boiler. ၁၃-၁၅ Arrangement of fire tube boilers.

၁၃.၆ Water Pump Controls

pump chiller control system boiler control system pump transfer pump၊ booster pump ႔

၁၃-၁၆ Typical level control system for pumps Water transfer pump (tank) (water level) control (၁) (Low level tank) water level o pump (၂) (High level tank) water level o pump (၃) (High level tank) water level pump


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၁၃.၇ AHU Controls ၁၃.၇.၁ Constant Air Volume(CAV) AHU

Air Handling Unit(AHU) Constant Air Volume(CAV) AHU Variable Air Volume(VAV) AHU Constant Air Volume(CAV) AHU control (၇)

၁၃-၁၇ Constant Air Volume Air Handling Unit (CAV AHU) control schematic

၁၃.၇.၂ Variable Air Volume (VAV) AHU

၁၃-၁၈ Control arrangement of a Variable Air Volume (VAV) AHU.

Commercial building variable air volume (VAV) system ႔ ႔ Variable Air Volume (VAV) system thermostats VAV box AHU fan VSD Distribution duct static pressure sensor Fan (speed) control duct (static pressure) VAV box AHU fan operation DDC control VAV box damper position BAS (monitor)

static pressure set point (fixed) ႔ static pressure set point (reset System static pressure AHU fan (energy consumption)


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VAV system control air conditioning system co o cooling VAV system (office building) VAV system

၁၃-၁၉ Variable Air Volume Air Handling Unit (VAV AHU) control schematic

၁၃-၂ Typical static pressure reset algorithm

Pressure dependent VAV box (self-balancing) VAV system r Static pressure sensor supply duct s c ssu s

Minimum set point AHU fan speed control algorithm AHU fan s VAV box 90% open position Control algorithm VAV box damper position (monitoring) AHU fan speed control VAV box damper


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(above 90%) ႔ static pressure set point VAV box damper (below 70%) static pressure set point VAV system CAV system ၂ % ႔

၁၃.၇.၃ VAV Box Control

၁၃-၂၁( ) VAV Box control VAV box pressure dependent pressure dependent Pressure

independent VAV box VAV box control velocity differential pressure sensor (space temperature) thermostat VAV box (air flow) control motorized damper VAV box (maximum air flow) (manimum air flow)

၁၃-၂၁( ) VAV Box control

VAV box VAV box control


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(၁) (space temperature) thermostat (space temperature) set point Cooling (space temperature) set point (volume flow rate)

(၂) Differential pressure sensor velocity ႔ Velocity (actual volume flow rate) ႔

(၃) (required flow) (maximum air flow) (manimum air flow) (actual flow) (required flow)

(၄) (actual flow) (required flow) controller actuator ႔(command) (actual flow) (required flow) controller actuator ႔(command)

ဤ (volume flow rate) control (space temperature)

၁၃-၂၁( ) Air flow maximum flow minimum flow

၁၃.၈ Fan Coil Unit (FCU) Controls

၁၃-၂၂ FCU control by retrun air temperature ၁၃-၂၃ FCU control by space temperature

Fan Coil Unit(FCU) on/off (type) control valve oo o (space temperature) set point


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control valve chilled water (flow rate) FCU device (meeting room) FCU occupancy sensor control Occupancy sensor (meeting room) ႔ (detect) FCU (၁ ) ႔ FCU ႔ s u o

(intelligent building) FCU facility booking system (meeting room) (user) facility booking system booking FCU controller enable Booking FCU

Table 13-1 FCU Input /Output point schedule Input /Output Variables DO AO DI AI Software 1 Return air temperature 1 High/Low Alarm 2 FAN On/Off Control 1 3 FAN On/Off Status 1 4 Fan Trip Status 1 Trip Alarm 5 Local /BAS Modes 1 6 Chilled Water Control Valve 1 7 Control Valve Position Feedback 1 Total: 1 1 3 2

၁၃-၂၄ Fan Coil Unit (FCU) DDC controller input/output

၁၃.၉ Ventilation Fan Controls (application) ventilation fan control

CO2 level ၊ CO level ၊ (temperature) ႔ control

၁၃.၉.၁ Ventilation Fan Control by Carbon Monoxide ႔ Ventilation Fan Control

o 55 :2009 A oo occu s c comm


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႔ 9 PPM m o ၁ ႔ ၉ ႔ s m c ႔ co Singapore Standards 553 - (formerly CP 13) 25 m

၁၃-၂၅ Basement car park monitoring system- Controller wiring diagram

႔ basement car park) mo o s s m c ႔ o ႔ s so 9 ႔ su us s u o 25 ႔ su us

basement car park s m c ၊ s ႔ Basement car park ventilation fan fi m s s m oc m c “Fire Mode” ႔ basement car park fan

၁၃.၉.၂ Ventilation Fan Control by Carbon Dioxide (CO2 ႔ Ventilation Fan Control

၁၃-၂၆ Outdoor air control based on CO2 level

၁၃-၂၇ Ventilation control arrangement for maintaining a parameter in a space


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၌ o co c o carbon dioxide co c o ႔ occu s (outdoor air) ႔ s

႔ fresh air) ႔(fresh air) ႔ ႔ ႔(fresh air) CO2 Carbon D o 1000 PPM ႔(fresh air)

၁၃-၂၈ Ventilation control arrangement for maintaining a parameter in a space.

၁၃.၉.၃ Ventilation Fan Control by Temperature (Temperature Ventilation Fan Control

(mechanical rooms) ventilation fan 40°C Operator 40° ႔ ႔ (mechanical room) 40° ventilation fan ၊ 35°C ventilation fan 35°C 5°C ventilation fan

၁၃.၉.၄ Staricar Pressurization Fan

၁၃-၂၉ Ventilation control arrangement for maintaining static pressure in a space.


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P1= Pressurization system pressure P1>P2>P3 P1-P3>50 Pa Pressure P1 in staircase is greater than pressure P2 in Smoke stop lobby P2 is greater than pressure P3 of occupied space

၁၃-၃ Maintaining pressure differential without smoke stop lobby ssu s c s occupied area)

50 sc ssu s c s occupied ar smo -s o o

ssu s c s smo -s o o mo -s o o occu

Duty Cycling u c c s o

႔ u c c co o (oversized) u m

၁၃-၃၁ Duty cycling

Du c c o m ႔ s o u o o m u s o m mum o - m s priority) u c c o m

၁၃.၁ Lighting Control ၊

၅ ၁၂ ႔ L co o

ssu s c s ႔ ႔ 50 ႔ ႔ 110


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m ၊ ၊ co o

Lighting contro s o o co o s s m - o m H - o m ၊ ႔ Lo - o co o s s m s s (cost-effective) Lo - o co o s s m com om Lo - o co o s s m o uc

( ) Lighting control panels

( ) Relay panel/module

( ) Dimming panel

(ဃ) Light wall-box dimmers (slide, rotary)

( ) Manual switchers

( ) Maintained or momentary wall switches with pilot light. Occupancy sensors

( ) Photosensors

( ) Light sensors for dimmable ballast

( ) Infrared (IR) sensor receiver/transmitter

energy management software feature (၁) Fixed power reduction (e.g., tuning)

(၂) Occupancy-based, time-of-day (e.g., load cycling), and on/off control

(၃) Daylight harvesting

(၄) Demand limiting (e.g., peak demand load shedding)

(၅) Lumen depreciation compensation

၁၃.၁ .၁ Fixed Power Reduction ဤ

(consumption) lighting level Lighting level (energy consumption)

၁၃.၁ .၂ Occupancy-Based ၊ Time-of-Day and On/Off Control co sum o occu c - s co o

occu c ၊ - occu c s so co o ccu c s so ႔ c s c o ၁ ႔ switch off)

O o co o occu c s so c m m conference rooms ၊ restrooms ႔ u o c s


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co o occu c s so

၁၃.၁ .၃ Daylight Harvesting ႔ daylight artificial

lighting) ၊ o o Ambient s so u c ႔ co o o ou u us L daylig s co sum o ၄ ႔

၁၃.၁ .၄ Demand Limiting (pre-determined) demand(kW) ႔ co o

mm d m m ႔ m - mm u mm s co o s (e.g., time-delayed dimming) m s o co o s s m u ႔

(kW reduction) lux level) occupants) ႔

၁၃.၁ .၅ Lighting Control Systems - Energy management for lighting systems BAS lighting control (၁) Timed control if indoor lighting based on occupancy pattern (၂) Sensor control of light next to windows (၃) Timed or sensor control of car park lighting (၄) Timed or sensor control of light used for display or advertising (၅) Lighting control by occupancy sensing (၆) Brightness Sensor (၇) Dimmer Actuator (၈) Motion / Movement detector

Variable Air Volume Air Handling Unit(VAV AHU) CHW supply temperature blower ၏ power consumption) ႔ supply air temperature 11 13 ဒ AH ၊ AH CHW supply temperature 8.5°C ၍ s

Air con system ၏ AH ႔ coo co s s coo ႔ ou indoor air ၏ Hum ႔ H su m u Cooling coil


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၏ ၏ o m u um c o mo s u mo CHW supply temperature um c o ႔ co o s c Relative Humidity A

u m ႔

u m ႔ u m

( ) Switch off at specific times of day ( ) Switch off depending on heating or cooling demand ( ) Cycle equipment on and off repeatedly (ဃ) Switch on only on demand, e.g. Fresh air to conference rooms only whe occupied ( ) Optimum start/stop of heating or cooling plant ( ) Switch off if the projected consumption at any one time indicates that peak power demand will

be exceeded. ( ) Enthalpy control

Central cooling and/or heating plants Automatic control equipment manufacturer energy-efficiency control logic Specialized control system distributed controls ၊ programmable logic controllers or microprocessor-based systems architecture

primary equipment ၊ ancillary equipment overall system Standard control technology strategy strategy

• u s u o m um m u • o o u s

• c temperature • s c

• o mo o o c o o • co om c c

• ssu s • H co c c

• o o s u o m um • m s o co o

• ou o ou u • Variable-frequency drive control • ou ou u • ou s m ou u

• H ssu o o s u o m um

• s co o o m u o ssu

• o ou u m o system control

See Chapter 41 of the 2007 ASHRAE Handbook—HVAC Applications for more information on control strategies and optimization.


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၁၃.၁၁ Selection of Controls for Mechanical Ventilation Systems Table 13-2 Selection of controls for mechanical ventilation systems

Plant Control function Ventilation systems start/stop up to 30 kW heating

Time switch; resolution better than 15 minutes, spring reserve/battery back up

Ventilation systems start/stop 30–100 kW heating

Optimum start/stop recommended

Ventilation systems start/stop over 100 kW heating

Optimum start/stop required by current Building Regulations

Fresh air and exhaust dampers; tempered air systems

Open/closed linked with time control of plant

Fresh air, re-circulation and exhaust dampers; central air handling units; minimum fresh air

Full re-circulation when unoccupied; minimum fresh air position when occupied; minimum fresh air preferably controlled with respect to air quality

Fresh air, re-circulation and exhaust dampers; central air handling units; free cooling

Free cooling override of minimum fresh air from heating/cooling sequence; fresh air temperature high-limit or preferably enthalpy control

Tempered air systems Heating/cooling sequence for constant supply temperature; possible reset supply condition according to ambient temperature or summated demand if appropriate

Single zone air handling units Heating/cooling sequence from space or return air temperature; possible minimum supply air temperature to prevent dumping of cold air; systems for large spaces (lecture theatres, etc.) reset supply air temperature from return air

Multi-zone air handling units; common cooling coil

Re-heater batteries controlled with respect to space or return air temperature. Common cooling coil controlled from zone requiring most cooling; do not control cooling coil at constant off coil temperature, except in rare case of dew-point system

VAV air handling units: temperature Heating/cooling sequence for constant supply temperature; possible reset supply temperature according to ambient temperature or summated demand if appropriate

VAV air handling units; supply fan Speed or pitch control with respect to duct pressure 2/3 of the way along supply duct

VAV air handling units; supply fan, alternative methods

Speed or pitch control with respect to point near supply fan with reset from summated system demand, plus low


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limits; demand based control strategies based on VAV box positions can be used but can be unduly influenced by poorly sized boxes

VAV air handling units; extract fan Control with respect to supply/extract differential volume VAV boxes Control velocity between minimum and maximum with

respect to space temperature Dual duct air handling units Control hot and cold decks for a constant temperature.

Possible reset according to outside temperature or summated demand

Dual duct mixing boxes Mix hot and cold duct supplies according to space temperature

VAV dual duct Fans as for VAV; temperature as for dual duct Fan coil units Return air (or space) temperature control of heating &

cooling in sequence Induction units Heating and cooling control in sequence from space or

return air temperature; segregation of heating and cooling hydraulic distribution essential for efficient operation

Intermittently occupied areas Occupancy sensing controls with appropriate default values dependent upon system response

Humidification Control from space or return relative humidity, supply modulating high limit

De-humidification Over-ride temperature control of cooling coil to cool air below dew-point; re-heat via re heater batteries as per normal temperature control; supply temperature low limit may be required

-End-

Documents

Chapter - 13 Control Strategies