91
Part 4 - Diagnosis and T
roubleshooting
PC
Low pressure sensor connection on main
PCB is loose
1
Low pressure sensor has short-circuited
or failed
2
Insufficient refrigerant caused by
refrigerant leakage
3
The low pressure side is blocked, caused
by crushed or bent pipe, blocked EXV, or
dirty filter
4
The air side heat exchanger heat
exchange is poor in heating mode
5
The water flow rate is not sufficient in
cooling mode
6
Replace main PCB
Inspect the water system and fix the
error
Inspect the refrigerant system and fix the
error
Inspect the system and fix the error. If the
filter is blocked by ice, the piping should
be cleaned
Add refrigerant or inspect the system for
leaks
Replace the sensor
Ensure the sensor is connected properly
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
Notes:
1. For 30kW and 60kW units, low pressure sensor connection is port CN16 on the main PCB (labeled 9 in in Figure 4-2.1 in Part 4, 2.2 “Main PCB”) .
2. Measure the resistance among the three terminals of the pressure sensor. If the resistance is of the order of mega Ohms or infinite, the pressure sensor
has failed.
3. To check for insufficient refrigerant: An insufficiency of refrigerant causes compressor discharge temperature to be higher than normal, discharge and
suction pressures to be lower than normal and compressor current to be lower than normal, and may cause frosting to occur on the suction pipe. These
issues disappear once sufficient refrigerant has been charged into the system.
4. A low pressure side blockage causes compressor discharge temperature to be higher than normal, suction pressure to be lower than normal and
compressor current to be lower than normal, and may cause frosting to occur on the suction pipe. For normal system parameters.
5. Check air side heat exchanger, fan(s) and air outlets for dirt/blockages.
6. Check water side heat exchanger, water piping, circulator pumps and water flow switch for dirt/blockages.
