Mitsubishi Electric PQHY-P120THMU-A, Service Handbook

Page: 246 / 414

[
IX
Troubleshooting ]
- 237 - HWE09080 GB
1. Error Code
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 fre 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
2135
Cause Check method and remedy
(1) Heat source water circulation pump fault Operate the pump, and check for proper operation.
(2) Heater problem Check the heater, and correct any problems found.
(3) Poorly maintained field-installed water pipes Identify and remove the cause of water flow reduction, such
as a clogged strainer or cavitation.
(4) Dirty or clogged water heat exchanger Check the pressure difference between the unit's inlet and
outlet.
(5) Thermistor fault (TH5, TH8) Check thermistor resistance.
(6) Thermistor signal input circuit fault on the control
board Check the sensor reading on the LED.
(7) Improper installation of thermistor (TH5, TH8) Check the sensor reading on the LED.