Low
Mains On (Green Light) on Potterton Promax FSB 30HE

Your boiler is receiving electrical power and is ready to operate as normal.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

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.

What the manual says

Manufacturer manual

This indicates that there is electricity to the Boiler.

From this model's manual
Verified against the Potterton Boiler Promax Fsb 30he 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.

What causes this fault?

This is not a fault but a status indicator showing that the boiler is successfully connected to the mains electricity supply. It confirms that the internal control board is receiving power and the unit is in standby mode, ready to fire up when you turn on your heating or hot water. If the light is on but the boiler isn't heating, the issue likely lies with your external thermostat or a specific internal component rather than the power supply itself.

DIY fix possible

This fault may be fixable without an engineer. Check your manual first.

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