York YST - Section 5 - Troubleshooting; TABLE 3 - Operation Analysis Chart

JOHNSON CONTROLS
71
FORM 160.67-O2
ISSUE DATE: 10/9/2020
5
SECTION 5 – TROUBLESHOOTING
TABLE 3 - OPERATION ANALYSIS CHART
RESULTS POSSIBLE CAUSE REMEDY
1. Symptom: Abnormally High Discharge Pressure
Temperature di󰀨erence between
condensing temperature and water o󰀨
condenser higher than normal
Air in Condenser
High discharge pressure
Condenser tubes dirty or scaled
Clean condenser tubes. Check water
conditioning
High condenser water temperature
Reduce condenser water inlet
temperature. (Check cooling tower and
water circulation.)
Temperature di󰀨erence between
condenser water on and water o󰀨
higher than normal, with normal
evaporator pressure
Insu󰀩cient condensing water ow
Increase the quantity of water through
the condenser to proper value.
2. Symptom: Abnormally Low Suction Pressure
Temperature di󰀨erence between
leaving chilled liquid and refrigerant in
the evaporator greater than normal with
normal discharge temperature.
Insu󰀩cient charge of refrigerant
Check for leaks and charge refrigerant
into system,
Subcooler level valve problem Remove obstruction
Temperature di󰀨erence between
leaving chilled liquid and refrigerant
in the evaporator greater than normal
discharge temperature
Evaporator tubes dirty or restricted Clean evaporator tubes
Temperature of chilled liquid too low at
minimum rated speed
Insu󰀩cient load for system capacity
Check prerotation vane and Hot gas
valve operation and setting of low liquid
temperature cutout
3. Symptom: High Evaporator Pressure
High chilled liquid temperature
Prerotation vanes fail to open
Check the prerotation vane motor
positioning circuit
System overload
Be sure the vanes are wide open, Hot
gas valve is fully closed, and speed
us at maximum. System conditions
may dictate that the override controls
limit the chiller capacity until the load
decreases.
4. Symptom: Compressor or Turbine (KD Model) Oil Pressure
Low Oil pressure displayed on control
center; chiller will not start.
Oil pump running in wrong direction
Check rotation of oil pump (Electrical
Connections).
Oil pump not running.
Troubleshoot electrical problem with pil
pump motor and/or VSD on compressor
oil pump or turbine auxiliary oil pump
contractor.
5. Symptom: Compressor or Turbine (KD Model) High Oil Pressure