Medium
4.12 on Keston C30 / C35

Your boiler is providing central heating as expected, but it is failing to heat your domestic hot water, likely due to a sensor or valve getting stuck in the wrong position.

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.

What the manual says

Manufacturer manual

NO HW BUT CH ON

From this model's manual
Verified against the Keston/Keston C30 C35 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

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

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Related fault codes

4.10View →4.11View →

All 25 fault codes on the C30 / C35

Seeing a different code? Every code this model can display, in one place.

4.74.84.94.104.114.13204Fan FaultFlame LossFlame On Before Gas OnFlow Thermistor FaultFlow/Return ReversedHigh Mains VoltageIgnition LockoutLow Mains VoltageLow Water PressureOutside Sensor FaultOverheat LockoutPCB FaultReturn Thermistor FaultRoom Stat FaultSpare PCB Not SetToo Many RestartsWater Pressure

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