F26 on a Dimplex WPM heat pump manager platform: Frost protection: the flow temperature in heating operating mode is below 7C
Short answer
On a Dimplex heat pump, F26 means: Frost protection: the flow temperature in heating operating mode is below 7C. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Frost protection: the flow temperature in heating operating mode is below 7C.
Part involved: Flow temperature sensor.
When it shows: Manual: flow <7C in heating mode. GDHV article: flow <11C for 10 s on reverse-cycle ASHP, <5C on hot-gas-defrost units, or refrigerant upstream of liquefier <0C on reversible units.
Likely causes:
- Heating water temperature too low.
Is it safe?
| 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: Acknowledge after rectification.
What you can check
- Raise the heating curve a few degrees on the controller (GDHV).
- Temporarily select '2nd heat generator' operating mode for about an hour if a backup heater/boiler is fitted, then return to Winter/Auto (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
- Raise heating water temperature.
- Check flow rate, system volume and defrost behaviour.
Who to ask for: heat pump service engineer.
What you might notice
Sources
- 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