BoilerFaultCodesWhat the manual says
Manufacturer manualHot 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
Avoid the next call-out bill
A cover plan would handle faults like D.25: no call-out fees, no surprise bills.
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Related fault codes
All 135 fault codes on the ecoTEC pro 24
Seeing a different code? Every code this model can display, in one place.