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Midea M-Thermal Arctic HT R290 Mono fault F1

Protection for DC bus undervoltage

Heat pump

What it means

Protection triggered when the DC bus voltage on a single phase inverter PCB falls to or below 200VDC, indicating undervoltage condition on the inverter bus.

Likely causes

  1. Faulty inverter power module
  2. Faulty three-phase bridge rectifier (3Ph models)

Where to start

  1. Refer to Part 4 Appendix: Guide for identifying inverter PCB failure to determine PCB status before component replacement
  2. Measure DC voltage between Vout and GND at the pressure sensor connector on the Main Control PCB
  3. Measure DC voltage between Vcc and GND to confirm sensor supply voltage

The full answer, free

  • 6 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 144), 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.

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