F.737 on a Glow-worm GeniaAir: The condensation temperature in the refrigerant circuit is too high
Short answer
On a Glow-worm heat pump, F.737 means: The condensation temperature in the refrigerant circuit is too high. 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 condensation temperature in the refrigerant circuit is too high.
Part involved: The condensation temperature in the refrigerant circuit is too high.
Likely causes:
- Temperature in the environment circuit (cooling mode) or building circuit (heating mode) too high for compressor operation. Feed-in of external heat in the building circuit. Refrigerant circuit overfilled. Insufficient flow rate in the building circuit.
- Glow-worm trade page: Condensation temperature too high Building circuit flow rate too high or too low, lack of heat transfer into the building circuit, air in the building circuit, blocked or restricted filter or Y strainer, circulation pump, electronic expansion valve fault, refrigerant volume too high.
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
- Reduce or stop the transfer of heat from outside. 2. Check the back-up heater (heats up even though it is off in the sensor/actuator test?). 3. Check the EEV (does the EEV move to the limit stop? Use the sensor/actuator test). 4. Check the compressor outlet sensor, condenser outlet temperature sensor (TT135) and high-pressure sensor. 5. Check whether the service valves on the outdoor unit are open. 6. Check the air volume flow in cooling mode for sufficient flow rate. 7. Check the heating pump.
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.32 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026