Low
S.16 on Glow-worm Ultracom 2 SXI

Your boiler is performing a routine cooling cycle to clear internal gases after a burst of activity and is not currently in a fault state.

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

fan overrun

From this model's manual
Verified against the Glow Worm Ultracom 2 Sxi installation & service manual, page 55.
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 occurs when the boiler’s fan continues to run after the burner has switched off to safely purge remaining heat and combustion gases from the unit. It is a normal safety process that typically happens after a period of intense heating or hot water demand to ensure the internal components cool down correctly. Your boiler hasn't broken down; it is simply finishing its work cycle before it can start again.

DIY fix possible

Wait for 5-10 minutes to allow the cooling cycle to completeEnsure your thermostat is not calling for heat if you want the fan to stop soonerCheck that the boiler display changes to a different code after the cooling period

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