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MS8C / MS8H (208-230V)
DEFROST MODE (HEAT PUMP ONLY)
The front panel indicator will display an H1 code when the system is in defrost. The system will perform as indicated in the
figure 58.
DEFROST MODE
FIGURE 58
Protective Functions
Delays that normally protect the compressor are disabled during defrost cycles:
1. There is no three (3) minute minimum compressor time off delay between operating cycles.
2. There is no six (6) minute minimum compressor operating cycles.
Defrost Initiation
Defrost is controlled by the microprocessor and will be initiated when:
*
System is in heating mode,
*
System has been running for at least six (6) minutes, or
*
Successive heating operations of more than 45 minutes or accumulated heating time more than 90 minutes.
*
One of the conditions listed under defrost termination that last longer than three (3) minutes.
Defrost Termination
Defrost is controlled by the microprocessor and will be terminated when:
*
Outdoor coil temperature goes above 55ºF (13ºC) + 5ºF (+ 3ºC)
*
Defrost time is a maximum of ten (10) minutes.
Cold Blow Prevention
The system prevents cold air from blowing into space during heating operation. After three (3) minute time delay, one of the
following indoor fan cycles will occur:
*
If the indoor ambient temperature is
greater
than 75ºF (24ºC): If the coil temperature is equal to or greater than 104ºF
(40ºC) the indoor fan will run at low speed for 1 to 2 minutes. If during that time the coil temperature rises above 106ºF
(42ºC), the indoor fan will ramp to a preprogrammed heat speed for those conditions.
*
If the indoor ambient temperature is less than 75ºF (24ºC): If the coil temperature is equal to or greater than 106ºF (42ºC)
the indoor fan will run at low speed and within one minute, the indoor fan will ramp to preprogrammed heat speed for
those conditions.
Defrost Test Function
When the unit is in Heat mode and set temperature is 61 F (16 C), press ”+, -, +, -, +, -” successively for 5 seconds. The indoor
and outdoor unit will enter defrost test function.
