38 PB
OPERATION
Unit Heat Control Operation - Heat Pump Only Unit
Once the ambient temperature falls below the Heating Demand Threshold
(1.5 ˚F Below the Heat Set Point Temperature), the heating cycle begins. The fan is turned on 5 seconds before. Once the
ambient temperature has been raised to the Heat Satised Point (Set point + .25 ˚F), the compressor is turned off. The fan is
turned off 15 seconds later. The gure below illustrates the basic heat pump operation.
Satised
Point
Figure 348 (Heat Control (Heat Pump Only)
KHS10B10A Heat Pump Defrost Cycle Operation
The defrost in this unit is an active reverse cycle. The defrost control runs in the background and determines when a defrost
cycle is required. Once initiated, the defrost cycle runs to completion.
The defrost cycle can only be initiated when the heat pump is in operation. The compressor will not be turned off to avoid
activating the compressor’s time delay. The reversing valve will be switched to the cool mode position. The indoor fan/blower
will be turned off. Once the defrost cycle is nished, the system should re-enter a heating demand cycle if required.
When the heat pump run time is 60 minutes or greater with an outdoor coil temperature of 26F degrees or lower, the control
will run an active defrost for up to 6 minutes. When the temperature at the outdoor coil reaches 54F degrees, the heat pump
heat will resume.
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