4-5 Low

Remeha 4-5 Fault Code

Also written as 45 — same fault.

The Remeha 4-5 fault code means: your boiler is notifying you that it has successfully transitioned to its second, higher stage of heating output.. It appears on 3 Remeha models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Operating signal stage 2

What causes the Remeha 4-5 fault?

This code is not actually a fault, but a status update showing your boiler has increased its heat production to meet a higher demand. It occurs when your heating system realizes the building needs more warmth than the initial low-power setting can provide. The boiler is simply communicating that it has opened its gas valve further to run at full capacity.

This notification is more likely to appear during the winter months when outdoor temperatures drop and your home requires maximum heat output to stay warm.

DIY fix possible

This fault may be fixable without an engineer. Check your manual first.

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Remeha models that show the 4-5 fault code

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

Source

Remeha 4-5 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