Form O-Y P/N 273647R5, Page 43
IMPORTANT:
Do not release refrigerant to the atmosphere!
If required service procedures include the adding or removing of
refrigerant, the service technician must comply with all federal,
state and local laws. The procedures discussed in this manual
should only be performed by a qualified HVAC technician.
NOTE: Unit is equipped with a phase loss/phase reversal control. If system
does not start, check phase of electrical supply.
See Control Instructions,
Form CP-Y-D19 or Form
CP-Y - D21, for information
on the unit controller.
7.0 Troubleshooting
7.1 Troubleshooting - Refrigeration
General Refrigeration Circuit
SYMPTOM
POSSIBLE CAUSE
REMEDY
A. Compressor
will not start.
1. Power off, loose electrical connections or
fuse open.
1. Check disconnect switch, fuses and wiring. Replace parts or
repair as necessary
2. Compressor contactor not closing.
2. Check voltage to contactor coil, transformer, slave relay, system.
Replace parts as necessary.
3. Internal compressor thermal overload
open.
3. If compressor is hot, allow 2 hours to cool. See D. Below.
4. Compressor defective.
4. Check compressor for electrical failure. Compressor may be
seized; check refrigerant. If necessary, replace compressor.
5. High or low pressure switch open or
defective.
5. If manual reset (high pressure), reset switch. (Switch opens at
600 psi and will not reset above 400 psi.)
If auto reset (low pressure) does not reset and everything else is
OK, replace low pressure switch,
P/N 216380
.
B. Compressor
starts but
cuts out on
low pressure
(low pressure
switch
activates at 35
psig.)
1. Low refrigerant charge.
1. Check subcooling; see Paragraph 3.6.
2. Airflow restricted.
2. Check for dirty evaporator coil, dirty filters, dampers closed, iced
evaporator coil, and/or improper belt. Check motor amps. Check
duct design.
3. Restriction in refrigerant line.
3. Check subcooling and superheat (Paragraph 3.6). Check
operation of the thermal expansion valve. Check for pressure drop
across the filter drier.
4. Defective low pressure switch.
4. Check switch (opens 35 psi; closes 50 psi). If defective, replace
low pressure switch,
P/N 216380
.
C. Compressor
starts but
cuts out on
high pressure
switch.
1. Refrigerant overcharge.
1. Check subcooling; see Paragraph 3.6.
2. Condenser fan motor defective.
2. Check fan motor.
3. Condenser coil inlet obstructed or dirty.
3. Check coil and inlet clearances and for possible air recirculation.
4. Air or non-condensables in system.
4. Check high side equalized pressure reading with equivalent
outdoor temperature.
5. Defective high pressure switch.
5. Check switch (opens 600 psi; proof 700 psi; manual reset allowed
below 400 psi). If defective, replace high pressure switch,
P/N
216379
.
6. Restriction in discharge or liquid line.
6. Check subcooling and superheat (Paragraph 3.6). Check
operation of thermal expansion valves.
D. Compressor
cuts out
on thermal
overload.
1. Low voltage.
1. Check voltage.
2. Sustained high discharge pressure.
2. Check running amperage and conditions described in I.
3. High suction and discharge pressures.
3. Check thermal expansion valve operation, check for air in system.
4. Defective compressor overload.
4. If compressor is hot, allow compressor to cool for two hours.
Recheck for open circuit.
5. Improper refrigerant charge.
5. Check subcooling (Paragraph 3.6).
6. Bearings or pistons too tight.
6. Check for low oil level.
7. Allow time for compressor to cool.
7. Check dome temperature of the compressor.
E. Noisy
compressor.
1. Reverse rotation.
1. Check at startup. If the suction pressure rises and discharge
pressure drops, shut down the compressor. Switch the 3-phase
wiring connections.
2. Refrigerant overcharge.
2. Check pressures and subcooling (Paragraph 3.6).
3. Liquid flood back.
3. Check thermal expansion valve setting. Check subcooling for
refrigerant overcharge (Paragraph 3.6).
4. Tubing rattle.
4. Dampen tubing vibration by taping or clamping. Carefully bend
tubing away from contact where possible.
5. Compressor defective.
5. Check internal parts. Replace defective parts or compressor.
