Medium Warning
4.15 on Ideal Logic Max Heat

Your boiler is providing central heating for your radiators as normal, but is failing to heat your hot water tank or taps.

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.

Technical description

No HW But CH Ok

What causes this fault?

This fault occurs when the boiler's internal components or external controls fail to signal that the hot water needs heating, even though the central heating for your radiators is working fine. The most common reason is a faulty motor or sensor that prevents the heat from being diverted away from the radiators and toward your hot water cylinder.

Engineer required

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

Find a Gas Safe engineer
Search the official register →

Related fault codes

4.13View →

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on combis.

Read →

Boiler won't turn on — 9-step checklist

Work through these before the call-out.

Read →

Radiators cold at the bottom

Sludge build-up — needs flushing, not bleeding.

Read →