Error Code 2135 - Mitsubishi Electric PQHY-P72TYHMU-A Service Handbook

[ IX Troubleshooting ]
1. Error Code
2135
Water heat exchanger freeze up
2. Error definition and error detection method
1) If either of the following conditions is detected (first detection) during operation, the heat source unit stops, goes into the 3-
minute restart delay mode, and automatically restarts after three minutes.
Water outlet pipe temperature (TH8) of 4°C[39ºF] or below is detected.
All of the following conditions are continuously met for one minute during Heating-all or Heating-main operation: Compres-
sor frequency < Minimum frequency + 20 AND Evaporation temperature (Te) < -2ºC[28°F] AND Accumulator inlet pipe tem-
perature (TH5) ” 3°C[37ºF].
2) If the conditions above (1) are met again within 60 minutes of the first stoppage of the heat source unit (second detection),
the unit will make an abnormal stop, and the error code "2135" will appear on the LED.
3) If the conditions above (1) are met again after 60 minutes of the first stoppage of the heat source unit, it is considered the first
detection, and the sequence as described in section 1) above is followed.
4) For the 60 minutes from the time the heat source stopped is considered a preliminary error, and it is indicated on the LED.
3. Cause, check method and remedy
(1) Heat source water circulation pump fault
(2) Heater problem
(3) Poorly maintained field-installed water pipes
(4) Dirty or clogged water heat exchanger
(5) Thermistor fault (TH5, TH8)
(6) Thermistor signal input circuit fault on the control
board
(7) Improper installation of thermistor (TH5, TH8)
HWE09080
Cause Check method and remedy
Operate the pump, and check for proper operation.
Check the heater, and correct any problems found.
Identify and remove the cause of water flow reduction, such
as a clogged strainer or cavitation.
Check the pressure difference between the unit's inlet and
outlet.
Check thermistor resistance.
Check the sensor reading on the LED.
Check the sensor reading on the LED.
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