1-8
Clutch Relay (CR)
The Clutch Relay (CR) is located in the electrical
control panel. When the CR relay is energized, a set of
internal contacts will close to engage the compressor
clutch (CL) to start the refrigerant cycle.
Air Conditioning Relay (ACR)
The AirConditioningRelay(ACR) is located in the
electrical control panel. The ACR relay is energized
when the A/C Switch (ACS) is placed in the COOL
position. When the ACR relay is energized, a set of
normally open ACR contacts will close to allow the
ClutchRelay (CR) and CondenserFanRelay (CFR1)to
energize.Whende-energized,theACRrelaywillprevent
the clutch and condenser fans from being activated
during the hea ting mode of operat ion.
Heat Relay (HR)
The Heat Relay (HR) is located in the electrical
controlpanel.This relaywillenergizeonlywhentheA/C
Switch (ACS)is in t he HEAT position. Whenenergized,
aset ofnormally open HRcontactswill close to allowthe
thermostattocontroloperationoftheBoostPumpRelay
(BPR) and Reheat Coolant Valve (RCV) during the
heating mode. When the thermostat calls for heating,
poweris applied from thermostat plug J1, pin 1, through
theclosedHRcontactst oenergizetheBoostPumpRelay
(BPR) and Reheat Coolant Valve (RCV) and start the
flow of engine coolant for heating.
Heat Relay #2 (HR2)
TheHeatRelay#2(HR2)islocatedin theelectrical
control panel. T his relayis energizedduring thecooling
cycle mode (when the thermostat is calling for cooling)
and during the cooling with reheat mode (when the
thermostat i s calling for cooling only) to prevent the
heating circuit from being energized while in cooling
operation. The relay is de-energized during the cooling
with reheat mode to activate the heating control circuit
when the t hermostat i s not calling for cooling.
With the ACS switch in the COOL position and the
RHCS switch in the CYCLE or REHEAT position, and
when the thermostat calls for cooling, power is applied
from the thermostat plug no. J1, pi n no. 3, to energize
Heat Relay #2 (HR2). Energizingrelay HR2opens a set
of normally closedHR2contactsto prevent activationof
theheat ingcontrolcircuitwhileunitisinthecoolingcycle
mode.
With the ACS switch in the COOL position and the
RHCS switch in the REHEAT position, and when the
thermostat is not calling for cooling, power is removed
from thermostat plug J1, pin no. 3, to de-energize Heat
Relay#2(HR2).De-energizingrelayHR2closesasetof
normally closed HR2 contacts to activate the heating
control circuit enabling the system to provide heating
during the cooling with reheat mode.
Evaporator Fan Relay #1 (EFR1)
Evaporator Fan Relay #1 (EFR1) is located in the
electrical control panel. When the Air Conditioning
Switch (ACS) is placed in either the COOL or HEAT
position,EFR1relay isenergized.Whenenergized,aset
of internalEFR1contactsare closedto start Evaporator
Fan Motors (EM1 and EM2).
Evaporator Speed Relays #1 and #2 (ESR1 and ESR2)
TheEvaporatorSpeedRelays(ESR1andESR2)are
located in the electrical control panel. These relays will
onlyenergizewhentheA/CSwitch(ACS)isi ntheHEAT
position. When energized, normally closed ESR1 and
ESR2contactswillclosetostartlowspeedevaporatorfan
motor operation.
Condenser Fan Relay #1 (CFR1)
The Condenser Fan Relay #1 (CFR1) is located in
theelectricalcontrolpanel.WhentheA/CSwitch(ACS)
is placed in the COOL position, A/C Relay (ACR) is
energizedclosinga setof normallyopen ACR1contacts.
And, when the thermostat calls for cooling, power is
applied to thermostat plug J1, pin no. 3, to energize
CFR1 relay through the closed ACR1 contacts. When
energized,asetof normallyopen CFR1contactscloseto
startthe CondenserFan Motors (CM1, CM2 andCM3).
The Low Ambient Thermostat (LATH) and Freeze
Thermostat Switches (FTS), if installed, must also be
closed to energize the Condenser Fan Relay.
Condenser Speed Relay (CSR)
TheCondenserSpeed Relay (CSR) is located in the
electrical control panel. This relay is energized at the
same moment the Condenser Fan Relay i s energized
provided the Condenser Fan Speed Switch (CSR) is
closed.Whenenergized,theCSRrelay willopena setof
normally closed CSR1 contacts to operate condenser
fansonlowspeed. Ifthecondensercoilpressurereaches
theCFSswitchcutoutsetting,theCFSswitchwillopento
de-energize the Condenser Speed Relay (CSR).
De-energizing the CSR relay will close a set of normally
closed CSR1 contacts enabling the Condenser Fan
Motors(CM1,CM2andCM3)tooperateonhighspeed.
Boost Pump Relay (BPR)
The Boost Pump Relay (BPR) is located in the
electrical control panel. This relay is energized during
heating. When the Boost Pump Relay (BPR) i s
energized,asetofnormalopenBPRcontactswillcloseto
activate the Boost Pump Motor (BPM).
Low Voltage Cutout (LVCO)
The Low Voltage Cutout (LT CO) is located i n the
electricalcontrolpanel.If thisrelay detectsa lowvoltage
condition, LVCO contacts will open to de-energize
Clutch Relay (CR), which disengages the clutch.
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