Medium

Low Mains Voltage on Keston Combi 30

Your boiler has detected that the electrical supply coming into your home is lower than it needs to be to run safely and properly.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026

What the manual says

Manufacturer manual

Low Mains Voltage

From this model's manual

Verified against the Keston/Keston Combi 30 installation & service manual.

Engineer required

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

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All 14 fault codes on the Combi 30

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

Boiler Type Card Fault Fan Fault Flame Loss Flow Thermistor Fault Ignition Lockout Lockout 6 Low Water Pressure Outside Sensor Fault Overheat Lockout PCB Fault PCB Replacement Return Thermistor Fault Too Many Resets

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