Lennox FCM 85 Installation, Operating And Maintenance Manual page 76

MAINTENANCE DIAGNOSTIC
REFRIGERATION
FAULT
HP PROBLEMS AND HP CUT
OUTS
Strong variations of pressure (
2 to 3 bar) Thermostatic
Expansion Valve "hunting"
Very high discharge
temperature,
High amps measured at
compressor
FLEXYII_WSHP-IOM-1307-E
POSSIBLE CAUSE AND SYMPTOMS
Incorrect airflow rates
Incorrect water flow rate (Water cooled
rooftop only)
Moisture or contaminants in the
system
Condenser coil is obstructed
Water Filter is obstructed
(only for Water Cooled Rooftop)
Recycled Hot Air
Incorrect adjustment of the expansion
valve
Low refrigerant charge
Filter drier obstructed with gas bubbles
at the expansion valve inlet
Moisture in the system
Very high superheat, very hot
compressor
Four Way reversing valve possibly
blocked, abnormal noise from the
valve, low LP and increasing HP
SOLUTION
Heat pump mode:
Check the filter before the indoor coil
measure and estimate the airflow rate
increase the speed of the fan
Cooling mode:
Check the condenser fan (Amps)
Check water flow value
Summer operation
Several hours after the unit has
stopped, check the correspondence
between the measured pressure and
the outdoor temperature
If the circuit pressure is higher (<1bar)
than the saturated pressure
corresponding to the measured
outdoor temperature, there is
possibility that some contaminants are
present in the system.
Reclaim the refrigerant, and vacuum
the circuit (Ensure very low and slow
vacuum for R407c)
Recharge the unit
Check the condenser coil and clean is
necessary
Check the water filter and clean if
necessary
Check clearance around the
condenser
Refer to LP problems and LP cut out
section
Open the superheat adjustment on the
expansion valve.
Check the pressure drop on the filter
drier in the suction line
Check operation of the valve by going
through cycle inversions. Change if
necessary.
Refer to LP problems
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