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Midea M-Thermal Arctic HT R290 Mono fault P4

High discharge temperature protection

Heat pump

What it means

Protects the compressor from abnormally high discharge temperatures and transient spikes. Triggered when discharge temperature rises above 115°C.

Likely causes

  1. Abnormally high discharge temperature
  2. Transient temperature spikes in the compressor discharge line
  3. Low ambient temperature (T4<3°C) combined with low water-side temperature triggers freeze protection
  4. Water side temperature dropping below critical thresholds due to low flow, low ambient temperature, or system stoppage
  5. Abnormal state detected requiring compressor protection
  6. Set temperature reached (normal stop)
  7. Damage to cables
  8. Excessive number of connections
  9. Terminals not made to original specification
  10. Damage to seals
  11. Incorrect fitting of glands
  12. Abnormal system state detected

Where to start

  1. Monitor discharge temperature (Tp) and suction temperature (Th) during compressor operation
  2. Track compressor running time against 12 minute threshold for EA logic
  3. Measure discharge temperature and compare to 115°C threshold

The full answer, free

  • 28 more checks in order
  • The readings and component tests from the manual
  • How to put it right, step by step
  • The manual page for this fault (page 28), right under the answer
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Safety: Isolate the outdoor unit and any backup heater, and give the inverter capacitors time to discharge before you open the electrics. Anything on the refrigerant circuit needs F-gas certification.

From the Midea manual for the M-Thermal Arctic HT R290 Mono. Check the model on the data plate before you order parts.

Other Midea M-Thermal Arctic HT R290 Mono fault codes