Vaillant Boiler F28 Error Code (Reasons & Fixes) Re May 27, 2022

Vaillant Boiler F28 Error Code (Reasons & Fixes)

Vaillant Ecotec Plus (Heat Only) Boiler

Did you see the F28 fault code on your Vaillant boiler? Don’t worry; we’re here to help you understand what it means.

If you’re having issues with your Vaillant boiler, it’s worth looking at the boiler to find the error code/fault code. 

What’s a fault code, you may ask… Think of it as the signs on your car’s dashboard that we choose to ignore sometimes -Please don’t ignore these signs!

car dahsboard

When a boiler experience a problem, it will turn off or, as we call it in the heating world, ‘lockout’ to protect itself and prevent possible damages.

Your Vaillant boiler will then display an error code to give you (and the heating engineer) information on what the problem could be. The Vaillant F28 is one of the error codes typically seen on Vaillant boilers. Hence, in this blog, we’ll discuss everything you need to know about the Vaillant F28 error code, including the causes and fixes.

Note – you should always follow the boiler manual instructions, and even if you know what the fault code means, make sure that a Gas Safe engineer carries out the repairs.

About Vaillant Boilers

If we were to describe Vaillant in 3 words, they’d be revolutionary, reliable and quiet.

Vaillant was formed way back in 1874 by Johann Vaillant in Remscheid, Germany. Johann Vaillant, the tenth child in his family, founded his own workshop as a copper beater and pump maker.

Many inventions have been credited to Vaillant over the years, including modern-day central heating in 1924. Previously each room was heated individually by stoves or fireplaces until Vaillant introduced the central heating boiler that could heat multiple radiators simultaneously – revolutionising home heating.

The Vaillant boiler range has been given a Which? Best Buy award, and they have also been awarded a Quiet Mark Accreditation from the Noise Abatement Society for their quiet running boilers.

For a full timeline of the Vaillant history, click here.

Fixing the Vaillant boiler F28 Error

The F28 code can occur on models like the Vaillant Ecotec Pro, Ecotec Pro Plus and Turbomax Plus 824/828E. These Vaillant models display the F28 code after 3 failed ignition attempts.

You might be tempted to turn your boiler off and on again, but this ‘IT Crowd’ trick won’t work this time simply because the boiler has likely gone into ‘lockout’ mode. In this scenario, the best thing you can do is to call a Gas Safe engineer. Don’t attempt to fix the boiler yourself because it’s dangerous.

Vaillant boiler F28 error - causes

The F28 code is technically an ignition fault, but if you look closer, it can be caused by several underlying issues such as Gas valve faults and Gas supply faults.

Therefore, when you report this issue to a Gas Safe Engineer, they are most likely to inspect these elements first so they can narrow it down and know exactly what caused it and how to fix it; 

  • The wiring harness to the gas valve/gas valve is mechanically sound
  • Condensate pipe
  • Printed circuit board (PCB)

But why is ignition important in a boiler?

In simple terms, the ignition is needed to light up the gas, which then creates the flame that’s needed to heat the cold water in the boiler. 

Failing to ignite means that the water can’t be heated, which results in cold water delivered to your taps and circulating in your heating system. Not what you want on a cold day! 

Vaillant boiler F28 error - fixes

1. Gas Valve

Most of the time, Gas Safe Engineers find that the Gas valve is the root cause of the F28 Vaillant boiler fault code. Then they look into the wiring harness to the gas valve and the gas valve function.

A. Gas valve wiring

This wiring connects the gas valve to the printed circuit board (PCB).

Loose\damaged wiring means that the valve can’t communicate with the PCB as it should.

The PCB sends signals to the valve when to open and close. Without those signals, the gas valve won’t work, causing the boiler to shut down in some cases.

If your Gas Safe Engineer identified this as an issue, count yourself lucky because it’s a quick fix (and relatively cheap) 💸💸💸.

The Gas Safe Engineer should be able to fix the gas valve wiring. The cost starts from £100 and it will vary based on location and other factors. 

B. Gas valve function

Gas valves tend to get stuck and, on some occasions, wear out over time.

If the gas valve gets partly closed, the boiler won’t get the needed gas supply, meaning your Vaillant boiler will shut down and will display the error code F28. 

If your heating engineer can free the gas valve and it’s not completely worn out, they will do so. And if not, they’ll replace it with a new gas valve which may cost around £300 (including parts and labour).

2. Printed Circuit Board (PCB)

A Printed Circuit Board (PCB) is a vital part of your boiler. Think of it as the motherboard of a computer. 

In simple terms, the Printed Circuit Board (PCB) is the backbone that ties the boiler’s electrical components (such as the pump, thermostat, timer etc.) together in one spot and lets them talk to each other. If the PCB stops working, the boiler will completely shut down; for example, if it stops sending the right signals to the gas valve, the Vaillant boiler will lockout and display the F28 code.

A Gas Safe engineer will examine your PCB by running an electrical test. If the engineer finds fault with the PCB, they may be able to fix it, or they may need to replace it. Depending on the supplier and quality of the PCB, this could cost anywhere up to £500, plus installation costs.

At this point, if you’re weighing up your options, it might be worth considering if you wish to spend this chunk of money on an old boiler which is likely to break down again or invest in a new boiler with a longer warranty and a better efficiency rate, which can save you money on your heating bills.

3. Condensate Blockage

If the condensate pipe gets blocked, it won’t let the condensed flue gases out. This is quite harmful.

When it happens, the PCB will get a signal that the condensate pipe is blocked and immediately lock out the boiler. Then the code F28 will appear on your Vaillant.

This issue normally happens in winter when the toxic gases freeze in the pipe.

For £50-100, the Gas Safe engineer can defrost the pipe and ensure that it doesn’t happen again. 

Luckily, newer boilers such as the Worcester Bosch Greenstar Range have a smart feature called CondenseSure to stop condensate pipes from freezing.

4. Faulty Vaillant Electrodes

Electrodes are used to ignite the gas in your boiler, but they can’t ignite the gas if they’re faulty.

Like any other boiler part, these electrodes can suffer wear and tear over time, which causes your Vaillant boiler to lockout and show fault code F28. 

Your heating engineer will be able to examine the electrodes and advise if your electrodes need to be replaced. This might set you back several hundred pounds.

5. No gas to your home

The last and easiest issue to test and resolve. And it’s the only time we’ll ask you to check the issue by yourself! 

The code F28 could mean that there’s no gas being supplied to your home. You can easily check this by turning on other gas appliances (i.e. cooker) to see if they work or not. 

If the other gas appliances aren’t working either, chances are your gas supply has been turned off. In this case, you should call your energy company.

Not prepared to waste money on fixing your knackered Vaillant?

Then it’s time for a new boiler! When you buy a new or replacement boiler with WarmZilla, your boiler package will also include;

  • Your chosen boiler, along with the necessary flue kit needed for your central heating system
  • Installation by a qualified Gas Safe Engineer 
  • Removal of your old boiler and parts
  • A FREE system cleanse of your central heating system
  • Chemical Inhibitor for added protection for your new boiler
  • 10-year guarantee, which will be registered by WarmZilla after installation
  • A FREE magnetic system filter for ongoing protection
  • The Neomitis RF Digital Wireless Room Thermostat
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