Low
I3 on Ideal Optimum 001

Your boiler is operating normally and is currently receiving power from your home's mains electricity supply.

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

Mains electricity ON

Community-sourced, unverified
We could not tie this code to a specific manual. Treat it as indicative only.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

No action is required as this indicates the boiler is powered on and functioning as expected.

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Avoid the next call-out bill

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All 4 fault codes on the Optimum 001

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

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