5
Install Electrical Accessories
Refer to the individual instructions packaged with kits or
accessories when installing.
Start--Up
CAUTION
!
PERSONALINJURY HAZARD
Failure to follow this caution may result in personal
injury.
Wear safety glasses, protective clothing, and gloves when
handlingrefrigerantand observe the following:
SFrontseating servicevalves areequipped with Schradervalves.
CAUTION
!
ENVIRONMENTALHAZARD
Failure to follow this caution may result in env ironmental
damage.
Federalregulations requirethat you do not vent refrigerant to
the atmosphere. Recoverduring system repair or final unit
disposal.
CAUTION
!
UNITOPERATION AND SAFETY HAZARD
Failure to follow this caution may result in personal injury,
equipmentdamage or improper operation.
SDonot overcharge systemwith refrigerant.
SDonot operate unit in a vacuum or at negativepressure.
SDonot disable low pressureswitch in scrollcompressor
applications.
SCompressordome temperaturesmay be hot.

Followthese steps to properly start up system:

1. After system is evacuated, fully open liquid and vapor
service valves.
2. Unit is shipped with valve stem(s) front seated (closed) and
caps installed. Replace stem caps after system is opened to
refrigerant flow (back seated). Replace caps fin ger--tightand
tightenwith wrench an additional1/12 turn.
3. Close electricaldisconnectsto energize system.
4. Set room thermostat at desired temperature.Be sure set
pointis below indoor ambient temperature.
5. Set room thermostatto HEAT or COOL andfan control to
ON or AUTO mode, as desired. Operate unit for 15
minutes. Check system refrigerant charge.
24 VAC HOT R
C
W2
Y
G
R
C
RVS COOLING
C
W2
HP THERMOSTAT TYPICAL
FAN COIL HEAT
PUMP
G
O
E
W2
E
W3
R
Y
24 VAC COM
HEAT STAGE 2
COOL/HEAT
STAGE 1
INDOOR FAN
EMERGENCY
HEAT
O
*
*
*
IF AVAILABLE
*
LEGEND
24-V FACTORY WIRING
24-V FIELD WIRING
FIELD SPLICE CONNECTION
OUTDOOR THERMOSTAT
EMERGENCY HEAT RELAY
SUPPLEMENTAL HEAT RELAY
SHR
EHR
ODT
A02325/ A97413
Fig.8 --Generic Wiring Diagrams
(See Thermostat Installation Instructio ns
forspecific unit combinations)
Sequenceof Operation
NOTE: Defrost control boardis equipped with 5 minute lockout
timer that is initiated upon any interruptionof power.
Turn on power to indoor and outdoor units. Transformer is
energized.
Cooling
On a call for cooling, thermostat makes circuits R--O, R--Y,and
R--G. Circuit R--Oen ergizes reversing valve, switching it to
cooling position. CircuitR--Y sends low voltage throughthe
safetiesand energizes the T1 terminalon the circuit board. If the
compressor has beenoff for 5 minutes, or power has not been
cycled for 5 minutes, the OF2 relay and T2 terminal will energize.
This willclose the contactor, and startthe outdoor fan motor and
compressor.
When the cycleis complete, R--Yis turned off, stopping the
compressorand outdoor fan. The 5 minute time guard begins
counting. Compressorwill not come on again until this delay
expires.In the event of a power interruption, thetime guard will
notallow another cycle for5 minutes.
NOTE: If the indoor blower off delayis enabled, it will run up to
anadditional 90 secondsto increase systemefficiency.
Heating
On a call for heating, thermostat makes circuits R --Y and R--G.
CircuitR--Y sends low voltage throughthe safeties and energizes
theT1 terminal on the circuit board.T1 energizesthe defrost logic
circuit.If the compressorhas been off for 5 minutes,or power
has not been cycled for 5 minutes, the OF2 relay and T2 terminal
will energize.This will close the contactor,start the outdoor fan
motorand compressor.
When the cycleis complete, R--Yis turned off , stopping the
compressorand outdoor fan. The 5 minute time guard begins
counting. Compressor will not co me on again until this time delay
expires.In the event of a power interruption,the time guard will
notallow another cycle for5 minutes.

25HCB3 / 25HCC5