TROUBLE SHOOTING GUIDE FOR UNITS WITH DX COOLING
12
Complaint
Symptoms
Probable Cause
Recommended Action
Ref.
Note
1. Bubbles in sight
glass.
Lack of refrigerant.
Repair leak and charge.
1
2. Temperature
change in refrigerant
line through filter-
drier or solenoid stops
valve.
Clogged liquid line
filter-drier or
solenoid valve.
Charge filter-core or clean valve.
2
3. No flow or
refrigerant through
expansion valve.
Expansion valve
power assembly has
lost charge.
Replace expansion valve power
assembly.
6
4. Loss of capacity.
Obstructed
expansion valve.
Clean valve or replace, if
necessary.
5. Conditioned pace
too cold.
Contacts on control
thermostat stuck in
closed position.
Repair thermostat or replace, if
necessary.
a. Compressor
capacity control
range set too low.
a. Reset compressor capacity
control range.
K. Suction pressures too low.
6. Compressor short-
cycles.
b. Air-cooled
condenser operating
with low
temperature outdoor
air.
b. Consider controlling
condensing temperature with
condenser discharge air dampers
or fan control.
Trouble Analysis Notes
1.
Refrigerant Shortage
- The system must contain sufficient refrigerant charge to flood the sub-cooling tubes of the
condenser. If the system is short of charge, refrigerant gas enters the sub-cooling tubes, causing them to become part
of the condensing surface. This robs the condenser of its ability to sub-cool the liquid. Without sub-cooling, the
liquid leaves the condenser at saturation temperature and pressure. Therefore, any pressure drop within the liquid
line causes some of the liquid to flash; reducing the temperature of the remaining liquid to the saturation
temperature that corresponds to the lower pressure. Flash gas displaces liquid within the port of the expansion valve,
reducing the valve's capacity. This results in reduced evaporator capacity and a corresponding reduction in suction
pressure.
