Specifications

JOHNSON CONTROLS
168
FORM 150.72-NM1 (908)
Service and Troubleshooting
PROBLEM CAUSE SOLUTION
“MP / HPCO” FAULT 1. Compressor internal motor 1. Verify refrigerant charge is
protector (MP) open. 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. External overload tripped. 2. Determine cause and reset.
3. HPCO switch open. 3. See “High Press. Disch.”
Fault.
4. Defective HPCO switch. 4. Replace HPCO switch.
5. Defective CR relay. 5. Replace relay.
COMPRESSOR(S) WON’T 1. Demand not great enough. 1. No problem. Consult
START “Installation” Manual to aid
in understanding compres-
sor operation and capacity
control.
2. Defective water temperature 2. Compare the display with a
sensor. thermometer. Should be
within +/- 2 degrees. Refer
to Service section for RWT/
LWT temp./voltage table.
3. Contactor/Overload failure. 3. Replace defective part.
4. Compressor failure. 4. Diagnose cause of failure
and replace.
LACK OF COOLING EFFECT 1. Fouled evaporator surface. 1. Contact the local YORK
Low suction pressure will service representative.
be observed.
2. Improper ow through the 2. Reduce ow to within chiller
evaporator. design specs. See Limita-
tions in Installation section.
3. Low refrigerant charge. 3. Check subcooling and add
Low suction pressure will charge as needed.
be observed.
TROUBLESHOOTING (CONT’D)