Classic HVPA & HVPSA M&S 8.09-1
15700 - 18
HVAC Equipment
Problem/Symptom
Likely Cause(s)
Correction
Low head - high vapor
pressures.
Flow check piston size too large.
Defective compressor valves.
Incorrect capillary tubes.
1.
2.
3.
Change to correct size piston.
Replace compressor.
Replace coil assembly.
1.
2.
Low vapor - cool com-
pressor - iced indoor coil.
Low indoor air flow.
Operating below 55°F outdoors.
Moisture in system.
1.
2.
3.
Increase speed of blower or reduce
restriction - replace air filter.
Add low ambient kit.
Recover refrigerant - evacuate and
recharge - add filter drier.
1.
2.
3.
High vapor pressure.
Excessive load.
Defective compressor.
1.
2.
Recheck load calculation.
Replace.
1.
2.
Fluctuating head and
vapor pressures..
TXV hunting.
Air or non-condensibles in sys-
tem.
1.
2.
Check TXV bulb clamp - check air distribu-
tion on coil - replace TXV.
Recover refrigerant, evacuate and
recharge.
1.
2.
Gurgle or pulsing noise
at expansion device or
liquid line.
Air or non-condensibles in sys-
tem.
1.
Recover refrigerant, evacuate and
recharge.
1.
Service Analyzer Charts
Compressor Overheating
Problem/Symptom
Likely Cause(s)
Correction
High superheat.
Low charge.
Faulty metering device.
High internal load.
Restriction in liquid line.
Low head pressure.
1.
2.
3.
4.
5.
Check system charge.
Restricted cap tube, TXV.
Power element superheat adjustment.
Foreign matter stopping flow.
Hot air (attic) entering room.
Heat source on; miswired or faulty
control.
Drier plugged.
Line kinked.
Low charge.
Operating in low ambient temperatures.
1.
2.
3.
4.
5.
Low voltage.
Loose wire connections.
Dirty or pitted compressor
contactor contacts.
Power company problem, trans-
former.
Undersized wire feeding unit.
1.
2.
3.
4.
Check wiring.
Replace contactor.
Have problem corrected before diagnosis
continues.
Correct and complete diagnosis.
1.
2.
3.
4.
High voltage.
Power company problem.
1.
Have problem corrected.
1.
Troubleshooting Chart (cont’d)
