Vaillant F28 fault code: no flame

Vaillant F28 means the boiler tried to light and didn’t detect a flame, so it stopped. Vaillant’s own description is that the flame signal was not detected during the ignition phase. Three quick checks clear it more often than you would expect: whether your other gas appliances work, whether a pre-payment meter has run out of credit, and whether the outdoor condensate pipe has frozen. If none of them helps, Vaillant says it is a case for one of its engineers.

What the Vaillant F28 fault code means

A boiler needs gas, a spark and a way of confirming that the flame has lit. F28 says the last step failed. That could be because no gas arrived, because the flame never lit, or because the boiler lost track of it. The code doesn’t say which, and that is why the manufacturer’s advice starts with the things you can see.

F29 is the close relative. It means that ignition after a flame loss during operation was unsuccessful. In other words, the boiler had been running, the flame went out and it couldn’t relight. Vaillant gives the same first checks for both.

Checks to make before you call anyone

Vaillant asks a homeowner to look at three things before anything else:

1. Other gas appliances. If your hob doesn’t light either, the gas supply is the problem, not the boiler.
2. Pre-payment credit. If you have a pre-payment gas meter, top it up. A meter that has run out of credit shuts off the gas.
3. The condensate pipe. In cold weather, look at the outdoor condensate pipe for ice. A frozen pipe is a known winter cause, and Vaillant links a video on defrosting one.

Resetting the boiler is the other step, and Vaillant says it often clears a fault or gets the boiler working again for a while. Your manual shows how to reset your model. Vaillant publishes manuals through its literature finder.

When Vaillant F28 needs an engineer

If the checks and a reset don’t clear F28, Vaillant says it is a case for a Vaillant engineer. You can call them or book through its customer portal, which the page names as myVaillant Web. Vaillant also lists F54, a fault in the gas supply, as a code that shows up together with F28 and F29. Check the gas and the credit again, clear any ice, and call an engineer if it stays.

The same applies if the code keeps returning. A boiler that locks out every few days needs someone to find out why, whether that is a failing part or a supply problem. If it is still under guarantee, contact Vaillant first so that the visit doesn’t affect your cover.

Safety with a Vaillant F28 lockout

Vaillant strongly advises against opening the boiler casing, because it is dangerous. If you smell gas, leave the property at once and call the National Gas Emergency Service on 0800 111 999. Don’t use switches or a lighter on the way out.

Related Vaillant and boiler fault codes

The pressure code is Vaillant F22, and it needs a different fix. Our guide to boiler fault codes explains how to read any code and which ones to leave to an engineer. Ideal has its own equivalent: see Ideal L2 for the flame loss lockout on those boilers.

When repeated lockouts mean a new boiler

A single ignition fault in a cold snap is easily forgiven. Several lockouts in one winter, on a boiler whose parts are getting hard to find, is a different story. A like-for-like combi boiler swap is the cheapest route, and the combi boiler prices page shows what each type costs fitted. When you are ready, get free quotes from local Gas Safe installers.

Source: Vaillant, boiler fault codes, read on 3 November. Vaillant’s guidance is used at your own risk.