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Heat pumps · Error codes · Warmflow
E29Warmflow

E29 on a Warmflow heat pump: Secondary Anti-freezing Protection

Short answer

On a Warmflow heat pump, E29 means: Secondary Anti-freezing Protection. The heat pump stops until the fault clears or is reset.

Reviewed 23 September 2026 · 3 sources

What it means

The manual says: Secondary Anti-freezing Protection.

Part involved: ambient / water temperature protection logic.

When it shows: Low ambient temperature winter anti-freeze protection (unit protects its water circuit).

Likely causes:

  • The ambient temperature is low.

Is it safe?

Does the heat pump stop?Yes
SeverityFault — clears by itself when the condition goes

The heat pump stops until the fault clears or is reset.

What you can check

  • Note the exact code shown on the controller (a photo helps) and report it to your installer or the manufacturer's service line.
  • Check the heat pump's supply breaker/isolator at the consumer unit is on (do not open any casing).
  • Check the outdoor unit is not blocked by snow, ice build-up or debris.
  • Leave the heat pump powered: frost protection needs a permanent electricity supply.

What the engineer will check

  • Test the operation of the ambient temperature sensor and re-connect/replace if necessary.

Who to ask for: heating / hydraulics.

Certification: Competent heating engineer.

What you might notice

Sources

A code explains what the controller detected, not a confirmed root cause.

Reviewed: 23 September 2026