Polar Air PTTW-10-EC+EH Series, Engineering Manual

Page: 24 / 33

THROUGH THE WALL UNIT 23
2.2.5 DEFROST MODE
2.2.5.1 HOT GAS BYPASS VALVE DEFROST FUNCTION
When the unit is in heating mode, the bypass valve will open or close when the following
conditions are fulfilled:
a. When OPT ” 28.4 ° F for 5 seconds, the bypass valve will open. Minimum per-cycle working
time is 2 minutes. If the indoor fan has been set at high speed originally, it will change to
medium speed automatically. If the indoor fan motor has been set at medium or low speed
originally, it will not change.
b. When OPT • 33.8 ° F, bypass valve will close. After one minute delay, the unit will check the
OPT continuously, and the bypass valve will open again when OPT ” 28.4 ° F.
c. When compressor is OFF, bypass valve will close after 10 seconds delay.
d. When the unit is OFF or OPT sensor has failed, bypass valve will close immediately.
2.2.5.2 FOUR WAY VALVE DEFROST FUNCTION
a. Defrost starting conditions:
In heating mode, when the unit has been heating for 30 minutes or more and the compressor
is continuously running for 5 minutes, the outdoor coil temperature sensor starts detecting the
outdoor coil temperature. When the sensor detects <23°F for 1 minute, the unit will begin to
defrost.
Defrost procedure:
1. Compressor, outdoor fan and indoor fan stop working.
2. 1 minute after, four-way valve closes.
3. Compressor turns on again after 1.5 minutes
b. Defrost ending conditions:
When defrosting, if the compressor has run for 5 minutes and OPT rises to 59 ° F, defrosting
will stop automatically and normal heating will resume.
Maximum defrosting time is 12 minutes (including compressor stoppage). If defrosting time is
greater than 12 minutes and the OPT temperature is still below 59 ° F, defrost cycle is stopped
and normal heating resumes.
Defrost ending procedure:
1. Outdoor fan turns on (compressor and indoor fan remain off).
2. 1 minute after, four-way valve opens.