157
YORK INTERNATIONAL
FORM 150.52-NM2 (1001)
COMPETENT PERSONS TROUBLESHOOTING GUIDE – CONT’D
PROBLEM
POSSIBLE CAUSE
ACTION
POSSIBLE CAUSE
ACTION
SYS # HIGH DSCH PRESS
Poor airflow through condenser coils.
Check for airflow restrictions caused by blockages
displayed (High discharge
on intake faces of air coils.
pressure trip)
Check for damaged fins/return bends.
Check for correct fan operation and direction of
rotation.
Check for non-condensables (air) in system.
Excessive refrigerant charge.
Check that the sub-cooling is correct.
Measured pressure is incorrect.
Check discharge transducer calibration and wiring.
SYS # HIGH OIL TEMP
High superheat.
Check TXV, chilled liquid temperature, and
displayed (High oil
condenser operation.
temperature)
Measured temperature is incorrect.
Check sensor calibration, location and wiring.
SYS # LOW OIL PRESS
Oil level low.
Add oil.
is displayed.
Measured pressure incorrect.
Check oil and suction transducer calibration
and wiring.
SYS # LOW SUCTION
Badly adjusted or faulty expansion
Check superheat.
displayed
valve.
Reduced evaporator performance.
Check for restricted chilled liquid flow.
Check for fouled tube surfaces.
Check superheat.
Low refrigerant charge.
Check subcooling is correct.
Check for leaks.
Restricted refrigerant flow.
Check for blocked filter / drier.
Check LLSV is operating correctly.
Measured pressure incorrect.
Check suction pressure transducer calibration and
wiring.
SYS # LOW CURR/MP/HP
Compressor current too low.
Check compressor mains supply, fuses, contactors
displayed
and wiring. Check mains supply voltage is within
tolerance.
Measured current is incorrect.
Check for defective current transformer (resistance
should be between 42 and 44 Ohms.)
Check calibration resistor is correctly fitted.
Compressor motor protector signal
Check motor protector and wiring.
failure.
Check compressor motor.
Mechanical high pressure cutout
Check compressor discharge valve is open.
trip.
Check cutout setting and wiring.
HIGH MTR CURR
Excessive refrigerant charge.
Check subcooling.
displayed (High
Condenser fans not operating.
Check overload trip point. Reset overload, if
motor current)
necessary. Check fan motor.
SYS # CURR LIMITING
High compressor motor current has
Check if liquid temperature is within operating limits.
displayed
activated unloading/limiting.
Check if ambient air temperature is above operating
(Compressor current
limits.
unloading.)
SYS # DSCH LIMITING
Discharge pressure unloading/limit-
Check chilled liquid temperature is within range.
displayed (Discharge
ing due to unit operating above
Check if ambient air temperature is
pressure unloading)
limit. See also SYS # DSCH
above design conditions.
LIMITING.
Check condenser oil cleanliness.
SYS # SUCT LIMITING
Low suction pressure has
Check charge (low subcooling).
displayed (Compressor
activated unloading/limiting
Check for high chilled liquid flow.
suction unloading)
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