Addison PR Series - Page 75

Page 75 of 84
Problem Probable Cause Solution
Compressor
Short Cycles
Thermostat location or malfunction
Check thermostat, check heat
anticipator setting
Improper refrigerant charge Check subcooling, verify superheat
Defective high or low pressure control Check high or low pressure switch
Cycling on internal overload Possible tight bearings – see above
Defective expansion valve Check TXV and superheat
Poor air distribution Check ductwork for recirculation
High discharge pressure See above – high discharge pressure
Leaking discharge valves in compressor See above – high suction pressure
Running Cycle Too
Long Or Unit
Operates Continuously
Refrigerant undercharged Check subcooling
Dirty filter or evaporator coil Check filter, coil and airflow
Dirty or clogged condenser coil Check coil and airflow
Air or other non-condensables in system
Check equalized high side pressure with
equivalent outdoor temperature
Defective compressor See above – high suction pressure
Restriction in suction and liquid line Check for restrictions in refrigerant circuit
Control contacts stuck
Check thermostat, shorts in wiring, slave
relay compressor contactor
Supply Air Temperature
Too High
Refrigerant undercharge or leak in system Check subcooling and check for leaks
Evaporator plugged with dirt or ice Check evaporator, airflow and filter
Improperly adjusted or defective expansion
valve
Check superheat and adjust TXV,
check bulb
Defective compressor Check compressor for proper operation
High discharge pressure See above- high discharge pressure
Airflow is too high Check external static pressure
Supply Air Temperature
Too Low
Airflow is too low
Check evaporator coil, filter, check for
closed dampers, grills, drive for loose parts,
belts, misalignment, check external
static pressure
Return air temperature too low Check entering air wet bulb conditions
Blower Motor
Not Running
Improper wiring Check wiring diagram
Defective motor Check motor controller
Defective thermostat or control circuit Check “R” and “G” Circuit
Motor o on overload protector Allow motor to cool, check amperage
Table 13.3: Refrigeration Circuit, Cont.
PR Series Installation, Operation, and Maintenance Manual