York MILLENNIUM YCAR0315 Installation Operation & Maintenance page 157

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