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7. Protection function introduction
● Outdoor coil temperature protection(T3)
T3>143.6°F, compressor stop working; T3< 129.2°F, compressor start working.
● Ambient temperature protection(T4) (Cooling only system T4=T3)
When 50°F≤ T4 < 140 °F, t h e units can work at the cooling condition.
When -4°F≤ T4 < 86 °F, th e units can work at the heating condition.
When T4 < 6.8 °F,If the electrical heater kit is installed in the indoor unit, the outdoor unit would provide a signal
to drive up the heater.
● Discharge temperature protection(T5)
When discharge temp. > 239 °F, the compressor will stop at the cooling condition.
When discharge temp. < 194 °F, the compressor will restart at the cooling condition.
When discharge temp. > 221 °F, the compressor will stop at the heating condition.
When discharge temp. < 167 °F, the compressor will restart at the heating condition.
● High pressure protection (HPS)
When high pressure > 580 PSIG, the compressor and outdoor fan will stop.
When high pressure < 435 PSIG, the compressor and outdoor fan will restart.
● Low pressure protection(PT)
Low pressure < 43.5 PSIG lasting for 5 min in cooling model, the compressor and outdoor fan will stop. System
will run again after 6 minutes.
● Module temperature protection (TF)
When TF>176 °F, the compressor and outdoor fan will stop.
When TF<145 °F, the compressor and outdoor fan will restart.
5. Compressor Crankcase heater description
Refrigerant migration during the off cycle can result in a noisy start up. Add a crankcase heater to minimize refrig-
eration migration, and to help eliminate any start up noise or bearing “wash out”.
All heaters must be located on the lower half of the compressor shell. Its purpose is to drive refrigerant from the
compressor shell during long off cycles, thus preventing damage to the compressor during start-up.
At initial start-up or after extended shutdown periods, make sure the heater is energized for at least 12 hours
before the compressor is started. (Disconnect switch on and wall thermostat off.)
● The crankcase heating start condition:
Start if crankcase heating zone can satisfy one of the three conditions,
1. First time to power on and T5>104℉
2. In process of defrosting
3.Compressor stops running for 4h and the outdoor ambient temp. T4 once lower than 50℉ or T5< 104℉ .
● The crankcase heating stop must meet condition:
Air discharge temp. T5≥113℉
6. Reversing valve introduction (heat pump only)
● Reversing valve
energizes at the heating conditions,and cut off at the cooling condition.
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