F.729 on a Glow-worm GeniaAir: The temperature at the compressor outlet is lower than the condensation temperature
Short answer
On a Glow-worm heat pump, F.729 means: The temperature at the compressor outlet is lower than the condensation temperature. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: The temperature at the compressor outlet is lower than the condensation temperature.
Part involved: The temperature at the compressor outlet is lower than the condensation temperat.
Likely causes:
- The compressor outlet temperature is lower than 0 °C for more than 10 minutes or the compressor outlet temperature is lower than -10 °C even though the heat pump is in the operating characteristics.
- Glow-worm trade page: Compressor outlet temperature too low Fault in the electrical connection of the compressor outlet temperature sensor, compressor outlet temperature sensor fault, fault in the electrical connection of the high pressure sensor, high pressure sensor fault, electronic expansion valve fault, 4 way valve fault, refrigerant volume ….
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no - the fault remains displayed until the cause is eliminated.
Manual reset: yes - after the cause is eliminated, press the reset button (indoor unit) or reset via the system control; if it recurs after several resets contact customer service.
What you can check
- Note the full code and text shown on the display (and the date/time it appeared). Check the outdoor unit's air inlet and outlet are not blocked by leaves, debris, snow or ice build-up and clear any loose debris from around it (do not open the casing, poke the fins or use tools). Glow-worm's MiPro Sense operating instructions say always contact your competent person in the event of a fault message; until they arrive you may select a limp-home (back-up heater) setting on the control, which is expensive to run. If you smell gas/solvent near the outdoor unit or hear hissing, switch the heat pump off at the isolator, keep ignition sources away and call an engineer.
What the engineer will check
- Check the high-pressure sensor. 2. Check that the EEV functions correctly. 3. Check the condenser outlet temperature sensor (subcooling). 4. Check whether the 4-port diverter valve is in the mid-position. Code/meaning Possible cause Measure.
Who to ask for: F-gas certified refrigeration engineer with heat pump experience (R290 flammable-refrigerant competence required for aroTHERM plus / GeniaAir).
Certification: F-gas Category I (Regulation (EU) 517/2014 as retained in GB) certificate; flammable (R290) refrigerant training for R290 units.
What you might notice
Sources
- GeniaAir Appliance Interface installation and maintenance instructions ↗ · 8000043014_01 · page HPIM 7 8000043014_01 p.31 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026