191
YORK INTERNATIONAL
FORM 201.18-NM3
COMPETENT PERSONS TROUBLESHOOTING GUIDE - CONT’D
PROBLEM
POSSIBLE CAUSE
ACTION
POSSIBLE CAUSE
ACTION
SYS # HIGH DSCH
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 DSCH TEMP
Suction superheat too high.
Check suction superheat is within range.
displayed (High discharge
Poor airflow through the condenser
Check for airflow restrictions caused by blockages
temperature)
coils.
on intake faces of air coils.
Measured temperature incorrect.
Check sensor calibration, location and wiring.
SYS # DSCH LIMITING
Discharge pressure unloading due to
Check chilled liquid temperature is within range.
displayed (Discharge
unit operating above load limit. See
Check if ambient air temperature is
pressure unloading)
also SYS # HIGH DSCH.
above design conditions.
SYS # HIGH OIL PRESS
Ball valve in oil circuit closed.
Check ball valves are in open position.
DIFF is displayed. (High oil
differential pressure.)
Dirty / blocked oil filter.
Check and change oil filter cartridge.
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 YLLSV 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 cut-out
Check compressor discharge valve is open.
trip.
Check cut-out setting and wiring.
No motor cooling.
Check motor cooling service valve is open.
Check operation of economizer and motor cooling
TEV’s and liquid solenoid valve.
SYS # CURR LIMITING
High compressor motor current has
Check if liquid temperature is within operating limits.
displayed
activated unloading.
Check if ambient air temperature is above operating
(Compressor current
limits.
unloading.)
11
Summary of Contents for MILLENNIUM YCAS 250
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