Troubleshooting; Diagnosing Problems For Which No Error Codes Are Available - Mitsubishi Electric CAHV-R450YA-HPB Installation & Operation Manual

6. Troubleshooting

Troubleshooting must be performed only by personnel certified by Mitsubishi Electric.

[1] Diagnosing Problems for which No Error Codes Are Available

If a problem occurs, please check the following. If a protection device has tripped and brought the unit to stop, resolve
the cause of the error before resuming operation.
Resuming operation without removing the causes of an error may damage the unit and its components.
Problem
The unit does not
operate.
The fuse in the control box
is not blown.
The fuse in the control box
is blown.
Automatic Start/Stop
thermistor has tripped.
The unit is in
operation, but
the water does
not heat up.
Water temperature is low.
Water temperature is high.
Check item
The power lamp on the
circuit board is not lit.
The power lamp on the
circuit board is lit.
Measure the circuit
resistance and the earth
resistance.
Water temperature is high.
Water temperature is low.
The water inlet/outlet
temperature differential is
normal.
The water inlet/outlet
temperature differential is
small.
Cause
The main power is not turned on.
The pump interlock circuit is not
connected.
The flow switch wiring is not connected. Connect the flow switch wiring to the system.
Short-circuited circuit or ground fault
The setting for the automatic Start/Stop
thermistor is too low.
The water-heating load is too high.
Low refrigerant charge due to a leak.
LEV fault
Compressor failure
High pressure is too high, or low
pressure is too low.
Water flow shortage
Problem with the external devices
52
Solution
Switch on the power.
Connect the pump interlock circuit wiring to the
system.
Resolve the cause, and replace the fuse.
Normal
Change the setting for the automatic Start/Stop
thermistor.
Install more units.
Perform a leakage test, repair the leaks, evacuate the
system, and charge the refrigerant circuit with
refrigerant.
Replace the LEV.
Replace the compressor.
Operate the units within the specified pressure range.
Increase the water flow rate.
Repair the devices.