York MILLENNIUM YCUL0045SC, Installation Operation & Maintenance

Page: 141 / 172

YORK INTERNATIONAL
FORM 150.63-NM2
141
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 discharge air temp. 2. Compare the display with a
sensor. thermometer. Should be
/- 2 degrees. Refer
to Service section for Dis-
charge Air temp./voltage tbl.
3. Contactor/Overload failure 3. Replace defective part.
4. Compressor failure 4. Diagnose cause of failure
and replace.
LACK OF COOLING EFFECT 1. Dirty evaporator surface. 1. Contact the local YORK
Low suction pressure will service representative.
be observed.
2. Improper CFM through the 2. Verify nominal 400 CFM/ton
evaporator. airflow through evaporator
3. Low refrigerant charge. 3. Check subcooling and add
Low suction pressure will charge as needed.
be observed.
4