BoilerFaultCodesYour boiler is currently busy heating your hot water because your smart thermostat or external controller has told it to do so.
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: Hot water activation via eBus control
What causes this fault?
This code appears when your external smart controls or cylinder thermostat send a digital signal asking the boiler to focus on heating your hot water. It is a status message rather than a mechanical failure, confirming that the internal valve has successfully switched over to the water heating position. Your heating may pause briefly during this time because the boiler is prioritising your taps or hot water tank.
DIY fix possible
Check if your hot water timer is active on your external thermostatWait for the hot water tank to reach its set temperatureNo action is required as this is a status message, not a system failure
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A boiler cover plan would cover faults like D.25 — no call-out fees, no surprises.
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