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Daikin Altherma fault FA-00

Outdoor unit: abnormal high pressure, actuation of high pressure switch

Heat pump

What it means

Outdoor heat exchanger thermistor measures a too high temperature.

Likely causes

  1. Closed stop valve in the refrigerant circuit
  2. Refrigerant overcharge
  3. Non-condensables and/or humidity in the refrigerant circuit
  4. Clogged refrigerant circuit
  5. Faulty outdoor unit fan motor
  6. Faulty refrigerant pressure sensor
  7. Poor water flow through high pressure side plate heat exchanger
  8. Incorrect refrigerant charge
  9. High pressure switch confirmed faulty during checking procedure

Where to start

  1. Check that all stop valves of the refrigerant circuit are open
  2. Check if the refrigerant circuit is correctly charged
  3. Check for the presence of non-condensables and/or humidity in the refrigerant circuit

The full answer, free

  • 14 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 46), 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 Daikin manual for the Altherma. Check the model on the data plate before you order parts.

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