4.15 Medium

Ideal 4.15 Fault Code

Also written as 415 — same fault.

The Ideal 4.15 fault code means: your boiler is heating your radiators normally, but it is failing to provide hot water when you turn on your taps.. It appears on 8 Ideal 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: No DHW But CH Ok

What causes the Ideal 4.15 fault?

This fault happens because the internal mechanism that switches the boiler’s heat from your radiators to your hot water taps has become stuck or failed. Either the electronic motor has stopped moving or the internal valve has become clogged with debris, meaning the boiler doesn't 'realise' or physically cannot react when you turn on a hot tap. While your heating continues to work, the boiler remains locked in heating mode and cannot divert that warmth to your water supply.

Typical repair cost £120-£250 (including labour)

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 for a qualified engineer in your area.

Gas Safe Register →

Ideal models that show the 4.15 fault code

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

Source

Ideal 4.15 fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.

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