SM Split AH/AV Air Handler
SM Split AH/AV Air Handler8733826256 (2020/06)
24 | Troubleshooting
Subject to change without prior notice
Table 11 Unit Troubleshooting
UNIT SHORT
CYCLES
Unit Oversized Recalculate heating and or cooling loads.
Thermostat
If the thermostat is installed near a supply air grill,
relocate thermostat. Adjust the heat anticipator.
Wiring and Controls
Check for defective or improperly calibrated low-
pressure switch.
INSUFFICIENT
COOLING OR
HEATING
Unit Undersized
Recalculate heating and or cooling loads. If excessive,
possibly adding insulation and shading will rectify the
problem.
Loss of Conditioned Air by
Leakage
Check for leaks in duct work or introduction of ambient
air through doors or windows.
Airflow
Lack of adequate airflow or improper distribution of air.
Replace dirty filter.
Refrigerant Charge
Refrigerant charge low causing inefficient operation.
Compressor
Check for defective compressor. If discharge is too low
and suction pressure is too high, compressor is not
pumping properly. Replace compressor.
Reversing Valve
Defective reversing valve creating bypass of refrigerant
from discharge of suction side of compressor. Replace
reversing valve.
Operating Pressures
Compare unit operation pressures to the pressure/
temperature chart for the unit.
TXV
Check TXV for possible restriction or defect. Replace if
necessary.
Moisture, Non-condensables
The refrigerant system may be contaminated with
moisture or non-condensables. Reclaim refrigerant,
replace filter dryer, evacuate the refrigerant system, and
recharge with factory recommended charge.
BLOWER
OPERATES
BUT
COMPRESSOR
DOES NOT
Thermostat Check setting, calibration, and wiring.
Wiring
Check for loose or broken wires at compressor,
capacitor, or contactor.
Safety Controls
Check UPM board red default L.E.D. for Blink Code
Compressor
Overload Open
If the compressor is cool and the overload will not reset,
replace compressor.
Compressor
Motor Grounded
Internal winding grounded to the compressor shell.
Replace the compressor. If the compressor is burnt out,
install a suction filter dryer.
Compressor
Windings Open
After compressor has cooled, check continuity of the
compressor windings. If the windings are open, replace
the compressor.
Unit Troubleshooting
Problem Possible Cause Checks and Corrections
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