Chilled Water System Trouble Shooting

This is provided as a general guide to basic problems associated with Chilled Water Systems

Symptom = Chiller Short Cycles Rapidly
Cause = Air in System - Flow switch
Solution = Purge Air From System - Check Auto Air Vent

Symptom = Chiller Short Cycles
Cause = Low Water Quantity
Solution = Fit a Buffer Tank - or Increase its Size

Symptom = Chiller Temp Diff 3C or lower
Cause = Chiller Capacity Down
Solution = Fit a Buffer Tank - or Increase its Size

Symptom = Chiller Temp Diff 3C or lower
Cause = Water Flow Too High
Solution = Adjust Flow Using Wheel Valve

Symptom = Chiller Temp Diff 7C or higher
Cause = Water Flow too Low
Solution = Check Circuit for restrictions. Check Pump Size

Symptom = Pressure too high in heating
Cause = Incorrect Pressurisation Tank
Solution = Check Pressurisation Vessel Sizing

Symptom = Fan Coils - Insufficient Cooling
Cause = Check Commisioning Valves
Solution = Commisioning Valves must be set up properly

Symptom = Fan Coils - Insufficient Cooling
Cause = Water Temp too high
Solution = Reduce Water Flow Temp (minimum 4C)

Symptom = Chiller trips HP in Heating
Cause = Water Temp too high
Solution = Reduce Water Flow Temp (maximum 50C

Symptom = Pipework Freezes
Cause = Insufficient Glycol
Solution = Increase Glycol Concentration

Symptom = Pump Overheats
Cause = Check Pump Duty
Solution = Check Pump Capacity is high enough

Remember: Minimum Water Quantity is 15l/KW of cooling. If in doubt use a buffer tank.
Always fit Strainers, Automatic Air Vents, Drain Points and Shut Off Valves.
Always fit a bypass and wheel valve in parralel with chiller to adjust water flow

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McQuay Model PDAN Fault code

Fault and Protection Codes for Applied PDAN Control Board

Fault code = CE
Description = Communication Error
Cause for the fault = 1. Cable not plugged in properly on either LUI or relay board.
2. Defective cable.

Fault code = Sh
Description = Missing Shunt
Cause for the fault = The user configurable shunt for System Select, Control Select Off Fan Cycle, and/or Hydronic Valve is
missing or not placed properly.

Fault code = E1
Description = Problem with IAS
Cause for the fault = Indoor Air Sensor missing or short

Fault code = E2
Description = Problem with ICS
Cause for the fault = Indoor Coil Sensor missing or short.

Fault code = E3
Description = Problem with OCS
Cause for the fault = Outdoor Coil Sensor missing or short.

Fault code = E4
Description = Problem with OAS
Cause for the fault = Outdoor Air Sensor missing or short.

Fault code = E5
Description = Problem with HFLO Sensor
Cause for the fault = HFLO Sensor missing or short on control board or heating medium >250ºF. Check for installation /
connection of HFLO sensor. Should be on coil return line.

Protection code = CF
Description = Coil Freeze Protection
Cause for the fault = Indoor coil temperature has been below 32ºF for 5 minutes.
Protection feature and the displayed code are dismissed when indoor coil temperature rises above 49ºF.

Protection code = Rf
Description = Room Freeze Protection
Cause for the fault = Indoor air temperature has dropped below 41ºF. Protection feature and the displayed code are
dismissed when indoor room temperature rises at and above 50ºF.

Protection code = hI
Description = High Room Temperature
Cause for the fault = Indoor air temperature is 5 degrees above maximum setpoint limit. Protection feature and the displayed
code are dismissed when indoor coil temperature rises above 50ºF.

Protection code = Lo
Description = Low Room Temperature
Cause for the fault = Indoor air temperature is 5 degrees below minimum setpoint limit.

Protection code = LA
Description = Low Ambient Lockout
Cause for the fault = Outdoor air temperature is below 25ºF.


Solid State Digital Controls – Local User Interface Display Codes

Fault code = LC
Description = Control Lockout –
Cause for the fault = Displays for 5 seconds when any button is pushed when in the "lockout mode".

Fault code = nL
Description = Control Lockout – Normal Control
Cause for the fault = Displays for 5 seconds to confirm normal mode of operation when control lockout turned off.

Fault code = CL
Description = Damper Closed
Cause for the fault = Control setup indicator damper is in "closed" mode.

Fault code = AU
Description = Auto Damper
Cause for the fault = Control setup indicator damper is in "automatic" mode.

Fault code = Au
Description = Auto HP/E
Cause for the fault = Control setup indicator heat pump electric is in automatic changeover mode (HP/E).

Fault code = bY
Description = HP/E Bypass
Cause for the fault = Control setup indicator, electric heat is bypassed when OCS > 40˚.

Fault code = CF
Description = Coil Freeze Protection
Cause for the fault = Indoor coil is ≤ 32˚ for at least 5 minutes. Compressor and outdoor fan stop and indoor fan continues
to run for active defrost.

Fault code = rF
Description = Room Freeze Protection
Cause for the fault = Room temperature < 41˚. Damper closes (Premium board) and unit goes into heat mode.

Fault code = Lo
Description = Coil freeze protection
Cause for the fault = Room temperature is 5˚ below set point.

Fault code = Lo
Description = Coil freeze protection
Cause for the fault = Room temperature is 5˚ below set point.

Fault code = Hi
Description = Temperature Limiting
Cause for the fault = Room temperature is 5˚ above set point.

Fault code = LA
Description = Low Ambient Lockout
Cause for the fault = Unit is in cooling mode and outdoor air < 25˚. Compressor will cut out.

Fault code = E1
Description = Indoor Air Sensor
Cause for the fault = Indoor Air Thermister Failure.

Fault code = E2
Description = Indoor Coil Sensor
Cause for the fault = Indoor Coil Thermister Failure.

Fault code = E3
Description = Outdoor Coil Sensor
Cause for the fault = Outdoor Coil Thermister Failure.

Fault code = E4
Description = Outdoor Air Sensor
Cause for the fault = Outdoor Air Thermister Failure.

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Mr Slim A-CONTROL CHECK CODE (U INDICATIONS)

INDICATIONS ON REMOTE CONTROL = U1
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) =
LED2 (RED) =
FAULTS = Unusual high pressure (63H) operated
STANDARD =
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = 1) Is ball valve open?
2) Check the indoor/outdoor short cycle

INDICATIONS ON REMOTE CONTROL = U2
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash Once
FAULTS = Discharge temperature is unusual/49C (inner thermostat operated) Refrigerant is insufficient
STANDARD =
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = 1) Check whether air filter is dirty to Clean it
2) Confirm whether gas leak or gas shortage occurred
3) Check the indoor/outdoor short cycle

INDICATIONS ON REMOTE CONTROL = U7
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash Once
FAULTS = Superheat occurred by low discharge
STANDARD =
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = 1) Has the discharge thermistor seperated?
2) Confirm whether electronic expansion valve has failed
3) Check CN LEV connector on the outdoor board

INDICATIONS ON REMOTE CONTROL = UE
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash Twice
FAULTS = Unusual high-pressure (63H) operated
STANDARD = *
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = 1) Is the ball valve open?
2) Check the indoor/outdoor short cycle
3) Is gas overcharged

INDICATIONS ON REMOTE CONTROL = UL
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash Twice
FAULTS = Unusual low-pressure (63L) operated
STANDARD = *
INVERTER =
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = 1) Is the ball valve open?
2) Confirm whether gas leak or gas shortage has occurred

INDICATIONS ON REMOTE CONTROL = Ud
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash 3 Times
FAULTS = Over raise is protected (overload operation is protected/Fan fault)
STANDARD = *
INVERTER =
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = 1) Check whether outdoor heat exchanger is dirty try to Clean it
2) Check the outdoor short cycle

INDICATIONS ON REMOTE CONTROL = U6
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash 4 Times
FAULTS = Compressor is intercepted by over-current (overload)
STANDARD = *
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = 1) After turning crank case heater on, have 12 hours or more passed?

INDICATIONS ON REMOTE CONTROL = U6
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash 4 Times
FAULTS = Powered module fault occurred
STANDARD =
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = (Replace the outdoor board)

INDICATIONS ON REMOTE CONTROL = UC
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash 4 Times
FAULTS = Compressor self protection activated
STANDARD = *
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = 1) Is ball valve open?

INDICATIONS ON REMOTE CONTROL = UF
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash 4 Times
FAULTS = Compressor is over-current (locked)
STANDARD = *
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = 1) Is ball valve open?
2) Is power capacity insufficient?

INDICATIONS ON REMOTE CONTROL = UH
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash 4 Times
FAULTS = Current sensor is unusual
STANDARD = *
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = 1) If outdoor board has been replaced: Check wiring and board setting

INDICATIONS ON REMOTE CONTROL = U3
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash 5 Times
FAULTS = Discharge thermistor (TH14) is open/short
STANDARD = *
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = TH4 connector on outdoor board seperated

INDICATIONS ON REMOTE CONTROL = U4
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash 5 Times
FAULTS = Pipe thermistor (TH3) is open/short
STANDARD = *
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = TH3 connector on outdoor board seperated

INDICATIONS ON REMOTE CONTROL = U4
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash 5 Times
FAULTS = 2-phase pipe thermistor (TH6) is open/short
STANDARD =
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = TH6 connector on outdoor board seperated

INDICATIONS ON REMOTE CONTROL = U4
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash 5 Times
FAULTS = Outdoor temperature thermistor (TH7) is open/short
STANDARD =
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = TH7 connector on outdoor board seperated

INDICATIONS ON REMOTE CONTROL = U4
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) = Flash 3 Times
LED2 (RED) = Flash 5 Times
FAULTS = Heat dissipation board thermistor (TH8) is open/short
STANDARD =
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = TH8 connector on outdoor board seperated

INDICATIONS ON REMOTE CONTROL = U5
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) =
LED2 (RED) =
FAULTS = Temperature of Heat dissipation board is unusual
STANDARD =
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = 1) Is air inlet/air outlet on outdoor unit blocked by an obstruction?

INDICATIONS ON REMOTE CONTROL = UP
INDICATIONS ON OUTDOOR UNIT
LED1 (GREEN) =
LED2 (RED) =
FAULTS = Compressor is intercepted by over-current
STANDARD =
INVERTER = *
DETECTED UNIT = Outdoor Unit
THE PART TO BE CHECKED = 1) Is ball valve open?
2) Is power capacity insufficient

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