OT ERROR Medium

Remeha OT ERROR Fault Code

Also written as OTERROR — same fault.

The Remeha OT ERROR fault code means: your boiler is staying on constantly because a safety sensor thinks the pipes are freezing, causing it to ignore your thermostat controls.. It appears on 4 Remeha 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: The frost thermostat calls for heat (contact closed) and overrides the Celcia 20 control, causing the boiler to operate continuously to achieve the flow set point.

What causes the Remeha OT ERROR fault?

This fault occurs when an external frost protection device becomes stuck in the 'on' position, sending a constant signal to the boiler. The boiler believes the pipes are at risk of freezing, so it continues to burn fuel and heat the water regardless of what your thermostat is telling it to do. This is usually caused by a faulty frost thermostat sensor or a short circuit in the wiring connecting that sensor to the main control board.

This fault is most common during late autumn and winter when temperatures drop, as this is when the frost protection system is actively cycling on and off.

Typical repair cost £120-220 (including labour)

Engineer required

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

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Remeha models that show the OT ERROR fault code

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

Source

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

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026