E 33 Medium

Chaffoteaux E 33 Fault Code

Also written as E33 — same fault.

The Chaffoteaux E 33 fault code means: your boiler has detected that the external thermostat connection for your underfloor heating is broken or disconnected, causing the system to stop that specific heating loop from running.. It appears on 2 Chaffoteaux models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Under floor heating thermostat open circuit
Typical repair cost £120-200 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Chaffoteaux models that show the E 33 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Chaffoteaux E 33 fault code information on this page is sourced and cross-checked against the official Chaffoteaux service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026