Johnson Controls YEWS Series, Installation, Operation And Maintanance Instructions

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9 TROUBLE SHOOTING
9.1 System Trouble Shooting Analysis
Possible Cause
1. Symptom: Low suction pressure
Faulty the pressure sensor
Faulty the chilled water temperature
sensor
Evaporator tubes dirty or scaled
Insufficient evaporator water flow
Improper value set of
“
LOW LELT
”
or "LEP SHUN DOWN"
Compressor not start from min load
Slide valve out of control
Low suction pressure
Insufficient refrigerant charge
Insufficient load for system capacity
2. Symptom: Oil level switch trip
Refrigerant overcharged
Faulty oil level switch
Faulty oil heater
Oil filter(outside the compressor)
clogged
Compressor not start from min load
Insufficient load for system capacity
Identification
Abnormal pressure value observed in panel
Abnormal temperature difference between
leaving chilled water and evaporation
temperature
Temperature difference between leaving
chilled water and evaporation temperature
greater than normal with normal discharge
temperature
Temperature difference between evaporator
water on and water off higher than nomal
“
LOW LELT
”
set should be greater than
the saturation temperature calculated
according to"LEP SHUN DOWN" set
Motor current greater normal after the Star-
Delta transfer
No unloading action while there is unloading
demand
Temperature between leaving chiller water
and cooling water is small and suction
pressure drop with the loading of compressor
Temperature difference between leaving
chilled water and evaporation temperature
greater than normal with high discharge
temperature
Temperature of chilled water too low with
low motor amperes
Chiller tripped in high frequency with low
discharge superheat
The oil is full in the bottom sightglass but the
oil level switch is open
No oil superheat in the oil sink
Notable temperature difference observed
before and after the oil filter
Motor current greater than normal after the
chiller started with low discharge superheat
Temperature difference evaporator water on
and water off very small
Remedy
Change pressure sensor
Change chilled water temperature sensor
Clean evaporator tubes, Check water
conditioning
Increase the quantity of water through
the evaporator to proper value
Reset the new
“
LOW LELT
”
or "LEP
SHUN DOWN" to proper value
Check compressor slide valve and slide
valve solenoid valve
"Check compressor slide valve and slide
valve solenoid valve;Set the compressor
unloading time to proper value"
I n c r e a s e t h e c o n d e s n e r w a t e r
temperature
Check for leaks and charge refrigerant
into system
Check slide valve operation and setting
of low water temperature cutout
Recover refrigerant to make the
discharge superheat and the subcooling
to proper value
Change oil level switch
Change oil heater
Clean the oil filter
Check compressor slide valve and slide
valve solenoid valve;Set the compressor
unloading time to proper value
Increase compressor min operation
current set
Successful problem solving requires an organized approach to define the problem, indentify the cause,and make the
proper correction. Sometimes it is possible that two relatively obvious problems combine to provide a set of symptoms
that can mislead the troubleshooter. Be aware of this possibility and avoid solving the "Wrong problem"
When an operating problem develops, compare all operating information on the OPERATING DISPLAY with normal
operating conditions. If an Operating Log has been maintained, the log can help determine what constitutes normal
operation for the compressor unit in that particular system.
YEWS-E Water Cooling Screw Chiller/Heat Pump
62