Low
S.02 on Glow-worm Ultracom 35 Store

Your boiler is performing a routine start-up check by running the internal pump for a few moments before lighting the burner.

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

pump pre-run

From this model's manual
Verified against the Glow Worm Ultracom 2 Cxi installation & service manual, page 52.
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 isn't actually a fault, but rather a normal part of the boiler's ignition sequence. It occurs when the system starts a 'pump pre-run' to ensure water is circulating correctly through the heat exchanger before the gas burner is allowed to light. This safety check prevents the boiler from overheating during the initial start-up phase.

DIY fix possible

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

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