F8, or L8 on some displays, is a lockout due to a parameter fault on an Ideal boiler. The manufacturer’s fault chart describes it as the PCB being unconfigured or faulty, or a gas valve fault.

This is engineer work. There is nothing a homeowner can usefully do with a parameter fault.

What F8 or L8 actually means

The control board holds configuration parameters that tell it what appliance it is fitted to and how that appliance should behave.

If those parameters are missing, corrupted or wrong, the boiler will not run. This most often appears after a PCB has been replaced and not configured for the specific model.

What you can safely check yourself

Nothing. If the boiler has recently had a new PCB fitted, mention that when you call, because it points straight at the likely cause.

When to stop, and why

What causes it beyond the simple checks

A replacement PCB that has not been configured for the appliance, a corrupted parameter set, a failed board, or a gas valve fault. If the boiler was working and then had a board fitted, configuration is the first thing to look at.

How Vantage can help

We are Gas Safe registered under 956889 and cover Hertfordshire, Bedfordshire and Cambridgeshire, with an emergency line answered 24 hours a day. Call us on 01462 506374. See also boiler repair and boiler servicing.

Frequently asked questions

Does F8 mean a new PCB?

Not necessarily. If a board has recently been fitted, it may simply need configuring correctly for your model.

Why did this appear right after a repair?

That is the classic pattern for a parameter fault. A new board needs setting up for the specific appliance.

Can I fix F8 myself?

No. Configuring a board requires the correct procedure and equipment.

Related fault codes

Other Ideal codes: L1 · L2 · LC · L6 · F1 · F2 · F3 · F4 · F5 · F6 · F7 · F9 · all boiler advice. See also boiler repair.

In Ideal’s own words

Ideal use different code sets across their ranges and generations. The definition above comes from The Ideal installation and servicing guide. If your boiler is a different model and the code behaves differently, check the manual for your appliance or ring us and we will tell you what it means on your unit.

When to call an engineer

If the checks above have not cleared it, the next steps are engineer work and the boiler should not be reset repeatedly in the meantime. Call Vantage Plumbing and Heating on 01462 506374. We are Gas Safe registered under 956889, the line is answered by a person at any hour of any day, and you get a price before anyone starts.

Need help today?

Call and speak to a person, any hour, any day of the year. Get a fixed price quote or call 01462 506374.