HP - B 2
Control Boards
20 SEER Heat Pump Model Control Boards
Overview
Communicating product air conditioners and heat
pump models feature an integrated control board with
communication capability, diagnostic capability,
defrost on demand logic, and advanced system control
functions. The integrated control board has had logic
enhancements and function upgrades since first
introduced.
Figure 1
Control features include:
• Sump heater control
• High pressure monitor logic
• Low pressure monitor logic
• Sensor and control voltage fault detection
• Anti-short cycle protection for compressors (Power
Interrupt Protection)
• Oil return mode
• Charge Assist
TM
capability
• Demand defrost cycle
• Time temperature mode when defrost malfunction
occurs
• Defrost mode fault detection
Sump Heater Control
Sump heat protects the compressor from liquid
migration. Liquid migration occurs when refrigerant
migrates during off cycle periods into the compressor
shell. Keeping the compressor shell warm during off
cycle periods, can prevent liquid migration. During
compressor run operation, the heater must be de-
energized to prevent the compressor motor winding
over temperature switch from opening due to an
overheated compressor.
De-energizing the sump heater also decreases system
power usage, increasing overall efficiency.
Sump heater operation at power up and
during a call for compressor operation
This control features advanced sump heat control. For
this function to operate properly, the system must
have a properly working Outdoor Ambient Air Sensor.
At power up, the board enters a warm up routine where
for up to 10 hours, the sump heater is energized. This
cycle will terminate if the compressor operates for at
least 4 minutes during the first 10 hours of power up.
After a warm up routine, the sump heater will always
be OFF if the outdoor air temperature is above 85F.
When the outdoor air temperature drops below 75F,
the sump heater will be energized until a compressor
runs.
The sump heater will remain off for 30 minutes after a
compressor has stopped running. The sump heaters
are wired in parallel (Figure 2.) to each other so if one
compressor runs, the sump heater cycle will affect
both compressors.
The system is designed so that a compressor and
sump heater will not run at the same time.
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