Vaillant aroTHERM fault F.734
Condensation temperature too low
Heat pumpWhat it means
Temperature in the heating circuit is too low, outside of the operating characteristics.
Likely causes
- The temperature in the heating circuit is too low, outside of the operating characteristics
- Refrigerant volume too low
Where to start
- Check the EEV (does the EEV move to the limit stop? Use the sensor/actuator test)
- Check the compressor inlet sensor
- Check the refrigerant filling volume (see technical data)
The full answer, free
- 40 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 35), right under the answer
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 Vaillant manual for the aroTHERM. Check the model on the data plate before you order parts.
Other Vaillant aroTHERM fault codes
- F.073Sensor fault: building circ. water pressure
- F.094Fault: vortex
- F.103Fault: spare part ident
- F.1117Compressor: phase failure
- F.22Heating installation filling pressure critically low
- F.514Sensor fault: compr. inlet temp
- F.517Sensor fault: compr. outlet temp
- F.519Sensor fault: building circuit return temp
- F.520Sensor fault: building circuit flow temp
- F.526Sensor fault: EEV outlet temp
- F.582Fault: EEV
- F.585Sensor fault: capac. outlet temp
- F.723Building circuit: pressure too low
- F.729Compressor outlet temperature too low
- F.731High-pressure switch open
- F.732Compressor outlet temperature too high
- F.733Evaporation temperature too low
- F.735Evaporation temperature too high
- F.737Condensation temperature too high
- F.741Building circuit: return temp. too low
- F.752Fault: frequency converter
- F.755Fault: 4-port valve position not correct
- F.774Sensor fault: air inlet temp
- F.788Building circuit: pump fault