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