York YD A, Operating & Maintenance, Page: 37 / 52

JOHNSON CONTROLS
37
FORM 160.69-O2
ISSUE DATE: 9/30/2020
5
SECTION 5 – TROUBLESHOOTING
TABLE 1 - OPERATION ANALYSIS CHART
RESULTS POSSIBLE CAUSE REMEDY
SYMPTOM: ABNORMALLY HIGH DISCHARGE PRESSURE
Temperature difference between
condensing temperature and water off
condenser
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 tempera-
ture. (Check cooling tower and water
circulation.)
Temperature difference between con -
denser water on and water off higher
than normal, with normal evaporator
pressure.
Insufficient condensing water flow.
Increase the quality of water through
the condenser to proper value.
SYMPTOM: ABNORMALLY LOW SUCTION PRESSURE
Temperature difference between
leaving chiller water and refrigerant in
evaporator greater than normal with
high discharge temperature.
Insufficient charge of refrigerant
Check for leaks and charge refrigerant
into system.
Variable orifice problem. Remove obstruction.
Temperature difference between leav -
ing chilled water and refrigerant in
evaporator greater than normal with
high discharge temperature.
Evaporator tubes dirty or restricted. Clean evaporator tubes.
Temperature of chilled water too low
with low motor amperes.
Insufficient load for system capacity.
Check prerotation vane motor operation
and setting of low water temperature
cutout.
SYMPTOM: HIGH EVAPORATOR PRESSURE
High chilled water temperature
Prerotation vanes fail to open.
Check the prerotation vane motor posi-
tioning circuit.
System overload.
Be sure the vanes are wide open (with-
out overloading the motor) until the load
decreases.
SYMPTOM: NO OIL PRESSURE WHEN SYSTEM START BUTTON PUSHED
Low oil pressure displayed on control
center; compressor will not start.
Oil pump running in wrong direction.
Check rotation of oil pump (Electrical
Connections)
Oil pump not running.
Troubleshoot electrical problem with oil
pump VSD.
SYMPTOM: UNUSUALLY HIGH OIL PRESSURE DEVELOPS WHEN OIL PUMP RUNS
Unusually high oil pressure is displayed
when the oil pressure display key is
pressed when the oil pump is running.
High oil pressure. Transducer defective. Replace low or high oil pressure trans-
ducer.