Medium
S.53 on Heatline Monza

Your boiler has temporarily held back its output because it senses that water is moving too slowly or cooling down too quickly between the heating pipes.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

Waiting cycle: temperature differential between heating fl ow and return is too high. If ∆T > 30, forcing to Pmin

From this model's manual
Verified against the Heatline Monza installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Check that all your radiator valves are fully open and not stuck shutEnsure your system pressure is set to the manufacturer's recommended level (usually 1.0 to 1.5 bar)Bleed all radiators in the house to remove any trapped air that might be restricting flow

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