Classic HVPA & HVPSA M&S 8.09-1
15700 - 17
HVAC Equipment
Troubleshooting Chart
WARNING
DISCONNECT ALL POWER TO UNIT BEFORE SERVICING. CONTACTOR
MAY BREAK ONLY ONE SIDE. FAILURE TO SHUT OFF POWER CAN
CAUSE ELECTRICAL SHOCK RESULTING IN PERSONAL INJURY OR DEATH.
Problem/Symptom
Likely Cause(s)
Correction
Unit will not run.
Power off or loose electrical
connection.
Thermostat out of calibration
- set too high.
Defective contactor.
Blown fuse/tripped breaker.
Transformer defective.
High pressure control open.
Low pressure control open.
1.
2.
3.
4.
5.
6.
7.
Check for correct voltage at unit discon-
nect. Check for correct voltage at contac-
tor in unit.
Reset.
Check for 24 volts at contactor coil -
replace if contacts are open.
Replace fuses/reset breaker.
Check wiring - replace transformer.
Reset.
Reset.
1.
2.
3.
4.
5.
6.
7.
Outdoor fan runs,
compressor doesn’t.
Run capacitor defective
Loose connection.
Compressor stuck, grounded
or open motor winding, open
internal overload.
Low voltage condition.
1.
2.
3.
4.
Replace.
Check for correct voltage at compressor
- check and tighten all connections.
Wait at least 2 hours for overload to
reset. If still open, replace the
compressor.
Add start kit components.
1.
2.
3.
4.
Insufficient cooling.
Improperly sized unit.
Improper indoor air flow.
Incorrect refrigerant charge.
Air, non-condensibles or mois-
ture in system.
1.
2.
3.
4.
Recalculate load.
Check - should be approximately 400 CFM
per ton.
Charge per procedure.
Recover refrigerant, evacuate and
recharge, add filter drier.
1.
2.
3.
4.
Compressor short cycles.
Incorrect voltage.
Defective overload protector.
Refrigerant undercharging.
1.
2.
3.
At compressor terminals, voltage must be
±10% of nameplate marking when unit is
operating.
Replace - check for correct voltage.
Add refrigerant.
1.
2.
3.
Registers sweat.
Low indoor air flow.
1.
Increase speed of blower or reduce
restriction - replace air filter.
1.
High head - low vapor
pressures.
Restriction in liquid line, expan-
sion device or filter drier.
Flow check piston size too small.
Incorrect capillary tubes.
1.
2.
3.
Remove or replace defective
component.
Change to correct size piston.
Change assembly coil.
1.
2.
3.
High head - high or
normal vapor
pressures - cooling
mode
.
Dirty outdoor coil.
Refrigerant overcharge.
Outdoor fan not running.
Air or non-condensibles in
system.
1.
2.
3.
4.
Clean coil.
Correct system charge.
Repair or replace.
Recover refrigerant, evacuate and
recharge.
1.
2.
3.
4.
