JOHNSON CONTROLS
151
SECTION 9 – SERVICE AND TROUBLESHOOTING
FORM 150.73-NM1
ISSUE DATE: 09/04/2020
9
TABLE 38 -
TROUBLESHOOTING (CONT’D)
PROBLEM
CAUSE
SOLUTION
“HIGH DISCHARGE PRESSURE”
FAULT
1. Condenser fans not operating or
operating backwards.
2. Too much refrigerant.
3. Air in refrigerant system.
4. Defective Discharge Pressure
Transducer.
1. Check Fan Motor, and Contactors.
Ensure Fan blows air upward.
2. Remove refrigerant.
3. Evacuate and recharge system.
4. Replace discharge pressure. See
SECTION 9 – SERVICE AND
TROUBLESHOOTING
for pressure/
voltage formula.
“MP / HPCO” FAULT
1. Compressor Internal Motor Protector
(MP) open.
2. External overload tripped.
3. HPCO Switch open.
4. Defective HPCO Switch.
5. Defective CR Relay.
1. Verify refrigerant charge is not
low. Verify superheat setting of
10°F - 15°F (5.6°C - 8.3°C). Verify
compressor is not over loaded.
2. Determine cause and reset.
3. See “High Press. Disch.” Fault.
4. Replace HPCO Switch.
5. Replace Relay.
COMPRESSOR(S) WON’T START
1. Demand not great enough.
2. Defective Water Temperature Sensor.
3. Contactor/Overload failure.
4. Compressor failure.
1. No problem. Consult “Installation”
Manual to aid in understanding
compressor operation and capacity
control.
2. Compare the display with
a thermometer. Should be
/- 2 degrees. See
SECTION 9 – SERVICE AND
TROUBLESHOOTING
for RWT/ LWT
temp./voltage table.
3. Replace defective part.
4. Diagnose cause of failure and
replace.
LACK OF COOLING EFFECT
1. Check DX Coil.
2. Improper air flow through the DX
Coil.
3. Low refrigerant charge. Low suction
pressure will be observed.
1. Contact the local Johnson Controls
service representative.
2. Reduce flow to within unit design
specs. See Limitations in Installation
Section.
3. Check subcooling and add charge as
needed.
Summary of Contents for YLUA0078
Page 10: ...JOHNSON CONTROLS 10 FORM 150 73 NM1 ISSUE DATE 09 04 2020 THIS PAGE INTENTIONALLY LEFT BLANK...
Page 14: ...JOHNSON CONTROLS 14 FORM 150 73 NM1 ISSUE DATE 09 04 2020 THIS PAGE INTENTIONALLY LEFT BLANK...
Page 42: ...JOHNSON CONTROLS 42 FORM 150 73 NM1 ISSUE DATE 09 04 2020 THIS PAGE INTENTIONALLY LEFT BLANK...
Page 100: ...JOHNSON CONTROLS 100 FORM 150 73 NM1 ISSUE DATE 09 04 2020 THIS PAGE INTENTIONALLY LEFT BLANK...
Page 130: ...JOHNSON CONTROLS 130 FORM 150 73 NM1 ISSUE DATE 09 04 2020 THIS PAGE INTENTIONALLY LEFT BLANK...
Page 152: ...JOHNSON CONTROLS 152 FORM 150 73 NM1 ISSUE DATE 09 04 2020 THIS PAGE INTENTIONALLY LEFT BLANK...