F22 on a Dimplex heat pump: Power transistor (IPM) overheating - system stopped to protect itself
Short answer
On a Dimplex heat pump, F22 means: Power transistor (IPM) overheating - system stopped to protect itself. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 2 sources
What it means
On the LA MI inverter outdoor air-to-water (LA 6/9/12/16 MI)
The manual says: Power transistor (IPM) overheating - system stopped to protect itself.
Part involved: Outdoor IPM temperature sensor.
When it shows: IPM temperature 95C; 3 times in 30 minutes.
Likely causes:
- Faulty outdoor fan motor.
- Faulty outdoor PCB.
On the WPM heat pump manager platform (error-code grouping)
The manual says: Domestic hot water: DHW temperatures in heat pump mode below 35C.
Part involved: DHW circuit / cylinder sensor.
When it shows: Heat pump cannot raise cylinder to at least 35C by compressor alone.
Likely causes:
- DHW circulating pump flow too low.
- Heating check valve defective.
- DHW sensor fault/position.
- Air in cylinder coil pipework (GDHV).
- 3-port valve not switching (GDHV).
Is it safe?
On the LA MI inverter outdoor air-to-water (LA 6/9/12/16 MI)
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: unknown.
Manual reset: Clear via control panel per Dimplex article (method shown as image).
On the WPM heat pump manager platform (error-code grouping)
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: After rectifying the fault the heat pump can be restarted; switching off the control voltage also acknowledges the fault (WPM Touch p.54). On text-display WPMs press Esc to acknowledge (EconPlus EN-16).
Manual reset: After repair installer resets 'Hot water performance' memory: Menu+Enter > Settings > Hot Water > Reset Max HP (GDHV 79000133011).
What you can check
On the LA MI inverter outdoor air-to-water (LA 6/9/12/16 MI)
- Check the outdoor unit air flow is not obstructed.
- Note the code and contact the installer or Dimplex service.
On the WPM heat pump manager platform (error-code grouping)
- Check the heating system pressure gauge reads 1.0-1.5 bar (GDHV).
- Note the fault code, the heat pump model (type plate) and controller software version shown in operating data, and contact the installer/Dimplex service.
What the engineer will check
On the LA MI inverter outdoor air-to-water (LA 6/9/12/16 MI)
- Isolate the heat pump from mains before any work.
- Check fan motor.
- Check refrigerant PCB.
Who to ask for: refrigeration / heat pump service engineer.
Certification: F-Gas (refrigerant handling) certification for any refrigerant-circuit work.
On the WPM heat pump manager platform (error-code grouping)
- Check DHW circulating pump flow and speed.
- Check check valves and 3-port valve.
- Bleed air from cylinder coil.
- Check DHW sensor position/reading.
- Reset Max HP learning.
Who to ask for: heating engineer.
What you might notice
Sources
- GDHV Help Centre article: i have f22 error on my la mi heat pump what does this mean ↗ · GDHV article (modified 2023-02) · page n/a (web article) · Reviewed 23 September 2026
- Dimplex WPM Touch heat pump manager - Operating instructions for users and specialists (Order no. 452117.66.02-EN, WPM3.13 / Display 1.15) ↗ · 452117.66.02-EN FD 0302 · page 55 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026