Vaillant ecoTEC F28 fault code

Vaillant F28 fault code explained

The F28 fault code is an ignition fault code and one is probably one of the most common fault codes found on a Vaillant ecoTEC boiler.

If you have a Vaillant ecoTEC boiler there is a very good chance you may experience this fault code at some point.

This fault code will cause your Vaillant boiler to stop working, leaving you without central heating or hot water.

The following video is a short clip of a broken Vaillant ecoTEC Plus boiler continually firing up for a few seconds unsuccessfully, then displaying an F28 fault code.

The F28 fault code essentially means that no flame inside the burner has been detected by the printed circuit board.

If you look in the Vaillant ecoTEC installation manual under the F28 fault code it states the following;

“Start-up failure: Ignit. unsuccessful – Failure during start-up or ignition unsuccessful. Gas pressure monitor or thermal cut-out has been triggered.”

“Check: Gas stopcock, gas flow pressure, gas valve assembly, air intake pipe (blockage, loosened screw), condensate route (blockage), multiple plug, cable harness, ignition transformer, ignition cable, ignition plug, ignition electrode, monitoring electrode, electronics, earthing, CO₂ setting”

Vaillant ecoTEC boilers like most modern boilers have a failsafe built into them to ensure that the boiler works safely. One of the fail safes in place is flame detection which is done via a process called flame rectification.

If the printed circuit board on the boiler doesn’t detect a flame then the boiler will attempt to light the burner three times, and if unsuccessful it will shut the boiler down and display an F28 fault code.

Like many fault codes, the F28 fault code does not actually tell you exactly what is wrong with the boiler. Unfortunately there are quite a few different possible cause of the F28 fault code. Possible causes include some of the following possibilities;

no gas supply to boiler(gas turned off), faulty gas valve, faulty printed circuit board(PCB), faulty spark electrode lead, blocked condensate trap, blocked or frozen condensate pipework or dirty ignition electrodes.

So as you can see there are many different components on a boiler that can cause the F28 fault code. In our experience working on Vaillant ecoTEC boilers the number one cause of the F28 fault code in general is either gas turned off, frozen blocked condensate pipework or gas valve.

This is why it is important to get a suitable Gas Safe registered heating engineer with experience on Vaillant ecoTEC boilers, otherwise you could waste money fitting parts that are unnecessary.

Gas valve failure was extremely uncommon on first generation ecoTEC boilers manufactured from 2005 – 2011.

However gas valve failure was quite a common fault on second generation ecoTEC Pro and Plus boilers manufactured from 2011 onwards.

If your gas valve is failing your boiler may work intermittently after a reset and display other faults codes as well as the F28 fault code, including the F29 fault code or the F54 fault code.

When to call a gas engineer to fix your boiler

If you are experiencing the F28 fault code on your Vaillant boiler, it is important to take action as soon as possible.

While some issues can be resolved by homeowners themselves, others require the expertise of a qualified Gas Safe registered heating engineer.

Because the F28 fault code can be caused by several different faulty parts, it is extremely important to get a suitable heating engineer with experience on Vaillant ecoTEC boilers, otherwise you could end up wasting money fitting parts to your boiler that are unnecessary.

Often you will be able to reset your boiler and get it working again if it’s showing an F28 fault code .

However in general this is just a short term solution and usually your boiler will probably stop working altogether at some point, leaving you without hot water and heating.

So it usually best to get a qualified heating engineer to have a look at your boiler at your earliest convenience.

How to prevent the F28 fault code

A lot of the time certain faults on a Vaillant ecoTEC boiler can be prevented with regular annual servicing and maintenance.

This is sometimes true of the F28 fault code as well.

However most of the parts on a Vaillant ecoTEC boiler that can cause the F28 fault code are non serviceable components.

These include; the gas valve, printed circuit board and ignition lead. There is nothing that can be done on a service to make these parts last any longer.

What an engineer can do to they help prevent the F28 fault code include;

ensuring the condensate trap and pipework are clean and have no blockages, ensuring the spark electrode assembly and heat exchanger are clean and that the boiler combustion parameters are correct by check them with a flue gas analyser.

Vaillant ecoTEC boilers affected by the F28 fault code

The F28 fault code on Vaillant ecoTEC boilers can affect any combination, system or heat-only boiler.

So this fault code can affect any Vaillant ecoTEC Pro combination boilers, any ecoTEC plus 800 Series combination boilers, any ecoTEC plus 600 series system boilers and any 400 series heat-only boilers.

Below is a list of ecoTEC boilers that can be affected by the F28 fault code;

• ecoTEC Pro 24 and ecoTEC Pro 28 natural gas combination boilers
• ecoTEC Plus 800 Series 824, 828, 831, 837 and 937 natural gas combination boilers
• ecoTEC Plus 800 Series 825, 832, 835, 838 and 938 natural gas combination boilers
• ecoTEC Plus 600 Series 612, 615, 618, 624, 630 and 637 natural gas system boilers
• ecoTEC Plus 400 Series 415, 418, 428 and 438 natural gas heat-only boilers

Frequently asked questions:

Is my boiler showing an F28 fault code worth repairing ?

Yes definitely, most of the time your broken Vaillant ecoTEC boiler displaying an F28 fault code will be worth repairing.

Obviously the cost to repair your boiler will be determined by which parts need to be replaced.

You would need a competent, Gas Safe registered heating engineer to have a look at your boiler and make an assessment to determine exactly which parts might need to be replaced.

Before replacing your boiler it is always worth getting a suitable Gas Safe registered heating engineer, with experience working on Vaillant ecoTEC boilers, to make an assessment of your boiler so you can determine whether it is worth fixing not.

Can I repair the F28 fault code myself?

Sometimes you can solve an F28 fault code yourself, you can ensure there is no issue with your gas supply by checking other gas appliances. If your boiler has a condensate pipe that runs externally you could check to make sure it hasn’t frozen.

Aside from that repairing the F28 fault code will usually require removing the cover of your boiler to replace parts which you are not legally allowed to do unless you are a Gas Safe registered heating engineer.

Is the F28 fault code dangerous?

No definitely not , the F28 fault code is not inherently dangerous, it’s the opposite. Modern Vaillant boilers are designed with fail safes in place to make sure that the boiler will only work if it safe to do so.

In general if you have an F28 fault code you may be able to reset your boiler for a period of time but then it will probably stop working altogether.

As such if your boiler is coming up with an F28 fault code, the best thing to do it get it repaired at your earliest convenience, by a suitable Gas Safe registered heating engineer – ideally one that has experience working on Vaillant boilers.