Low
S.02 on Glow-worm Ultimate3 System

Your boiler is simply preparing the water pump to start circulating heating before it ignites the flame, which is a normal part of the startup sequence.

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

Heating mode: Pump pre-run

From this model's manual
Verified against the Glow Worm Ultimate3 System installation & service manual, page 42.
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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