York YLAA0285SE Manual page 188

SECTION 9 – SERVICE AND TROUBLESHOOTING
PROBLEM
"MP / HPCO" FAULT
COMPRESSOR(S) WON'T
START
LACK OF COOLING EFFECT
188
TROUBLESHOOTING (CONT'D)
CAUSE
1. Compressor internal motor
protector (MP) open.
2. External overload tripped.
3. HPCO switch open.
4. Defective HPCO switch.
5. Defective CR relay.
1. Demand not great enough.
2. Defective water temperature
sensor.
3. Contactor/Overload failure.
4. Compressor failure.
1. Fouled evaporator surface.
Low suction pressure will
be observed.
2. Improper flow through the
evaporator.
3. Low refrigerant charge.
Low suction pressure will
be observed.
FORM 150.72-NM3 (1020)
ISSUE DATE 10/05/2020
SOLUTION
1. Verify refrigerant charge is
not low. Verify superheat
setting of °10 – 15 °F (5.6° –
8. 3 °C). Verify correct com-
pressor rotation. Verify
compressor is not over
loaded.
2. Determine cause and reset.
3. See "High Press. Disch."
Fault.
4. Replace HPCO switch.
5. Replace relay.
1. No problem. Consult
"Installation" Manual to aid
in understanding compres-
sor operation and capacity
control.
2. Compare the display with a
thermometer. Should be
within +/- 2 degrees. Refer
to Service section for RWT/
LWT temp./voltage table.
3. Replace defective part.
4. Diagnose cause of failure
and replace.
1. Contact the local Johnson
Controls service
representative.
2. Reduce flow to within chiller
design specs. See Limita-
tions in Installation section.
3. Check subcooling and add
charge as needed.
JOHNSON CONTROLS