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TABLE 8 – TROUBLESHOOTING GUIDE (CONT'D)
PROBLEM
SYS # HIGH DSCH
displayed
(High discharge
pressure trip)
SYS # HIGH DSCH TEMP
displayed (High
discharge temperature)
SYS # DSCH LIMITING
displayed
(Discharge pressure
unloading)
SYS # HIGH OIL PRESS
DIFF is displayed. (High
oil differential pressure)
SYS # LOW SUCTION
displayed
SYS # LOW CURR/
MP/HP displayed
SYS # CURR LIMITING
displayed
(Compressor current
operating limits.
YORK INTERNATIONAL
TROUBLESHOOTING GUIDE (CONT'D)
POSSIBLE CAUSE
Poor cooling liquid flow through the
condenser.
Excessive refrigerant charge.
Measured pressure is incorrect.
Suction superheat too high.
Measured temperature incorrect.
Discharge pressure unloading due
to unit operating above load limit.
See also SYS # HIGH DSCH.
Ball valve in oil circuit closed.
Dirty / blocked oil filter.
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.
No motor cooling.
High compressor motor current
has activated unloading.
ACTION
Check for restricted cooling liquid flow.
Check for non-condensables (air) in system.
Check sub-cooling is correct.
Check discharge transducer calibration and wiring.
Check suction superheat is within range.
Check for restricted cooling liquid flow.
Check sensor calibration, location and wiring.
Check chilled liquid temperature is within range.
Check ball valves are in open position.
Check and change oil filter cartridge.
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 YLLSV 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 motor cooling service valve is open.
Check operation of motor cooling, TEVs and liquid
solenoid valve.
Check liquid temperature is within operating limits.
Check if ambient air temperature is above unloading).
FORM 201.25-NM1 (302)
8
79
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