Usewiringwithatemperaturelimitation of 75 =C mini-
mum. Run the 208 or 230 volt, 60 hertz electric power supply through a fused disconnect switch to the control box of the unit and connect as shown in the wiring dia- gram located on the inside of the control access panel.
The unit must be electrically grounded in accordance with local codes or, in the absence of local codes, with the National Electrical Code ANSI/NFPA No. 70 (latest edition) or CSA C22.2 Part 1 (latest edition).
Power supply to the unit must be NEC Class 1 and must comply with all applicable codes. A fused disconnect switch should be field provided for the unit. The switch must be separate from all other circuits. If any of the wire supplied with the unit must be replaced, replacement wire must be of the type shown on the wiring diagram.
Electrical wiring must be sized to minimum circuit ampacity marked on the unit. Use copper conductors only. Each unit must be wired with a separate branch circuit and be properly fused.
OPERATION
Sequence of Operation
Cooling
When the thermostat is in the cooling mode, the O circuit is powered which energizes the reversing valve. Upon cooling demand, the thermostat closes circuit R toY and
G.Closing R to Y closes the unit contactor, starting the compressor and outdoor fan. The thermostat automati- cally closes R to G circuit which also brings on the indoor blower at the same time. Upon satisfying cooling demand, the thermostat will open the above circuits and open the main contactor, stopping the compressor and outdoor fan. If the unit is equipped with a time delay, the blower will continue to operate for 90 seconds which improves
system efficiency.
Heating
Upon heating demand, the thermostat closes circuit R to Y, which closes the unit contactor, starting the compressor and outdoor fan. The reversing valve is not energized in the heating mode.
Defrost Cycle
If the outdoor ambient conditions are such that frost forms on the outdoor coil, the defrost control monitors the need for and initiates and terminates defrost cycles as neces- sary to maintain system performance. The defrost control
is time/temperature initiated and temperature terminated with a maximum defrost time
Time between defrost cycles is preset at 60ominute intervals at the factory, but can be field adjusted between 30, 60 or 90 minutes. To field adjust time between defrost
cycles, place defrost time plug in the proper position (see Figure 3). For best performance in Region IV, the
PWC243 defrost interval should be adjusted to 30 min- utes.
Defrost control will initiate a defrost cycle if the time period has elapsed and the defrost sensor sees a temperature below freezing. At the start of a defrost cycle, the defrost control will energize the reversing valve solenoid, shifting the reversing valve and
The defrost control is also equipped with a setof pins to aid in troubleshooting of the defrost system (see Figure 3). The following is a brief outline of the testing of the defrost system.
. Defrost sensor must be closed, 32°F or below. If temperatures are such that switch will not close, jumper between defrost sensor terminals on the defrost control,
2.Start system in heating operation.
. Jumper test pins, A 1/4" quick connect terminal crimped onto a solid wire or brazing rod works well for test jumper. Closing test pins speeds up time interval by a factor of 256.
Defrost Control
Defrost
TestPins.,,,=i
Defro=/
TimePlug
Defrost Control Setting | Defrost Test Cycle Time | |
30 | minutes | 7 seconds |
60 | minutes | 14 seconds |
90 | minutes | 21 seconds |
FinHr
