Green Central avatar

Written by

Last updated:

F28 Vaillant Error Code: How To Fix & Causes

In the event that your Vaillant boiler struggles to ignite, an F28 Vaillant error code will be displayed. Your F28 Fault Code is typically an F code on the display of your Vaillant boiler. You should familiarize yourself with what this means and what you can do about it. The F28 Fault Code is normally displayed as a result of problems with the system’s control board or gas valves.

In this blog, we’ll explain what the F28 Vaillant error code means and what you can do to repair the problem and have your boiler back up and running in no time.

Fill out the form if you want a call back for a Gas Safe boiler servicing quotation anywhere in the country.

How do I fix the Vaillant boiler F28 fault code?

Vaillant logo

If on your Vaillant boiler display you see a fault code, you may be tempted to just restart it and disregard the warning.

However, this is unlikely to address the problem, and your Vaillant boiler will eventually quit working for three reasons:

  • To guard against boiler damage
  • So it can keep everyone on the premises safe
  • To irritate you on a cold day

It is also critical not to tamper with the boiler or open the casing oneself since this might be harmful. Instead, you should have your Vaillant boiler checked and repaired by a registered Gas Safe Engineer.

Check out: What does it mean to be a Gas Safe registered engineer?

If you see the Vaillant boiler F28 error code on your Vaillant boiler, it’s likely that your Vaillant boiler has failed three ignition attempts and has shut down. In order to fix this issue, you’ll need to either reset the boiler manually or contact a Gas Safe engineer for assistance as it’s not as simple as a reset button.

If you choose to reset the boiler manually, you’ll need to turn off all power to the unit and wait at least 15 minutes before attempting to restart it.

Simply said, ignition is required for your heating system, which then produces the flame required to heat the cold water to hot water in the boiler. Failure to ignite implies that the water cannot be heated, resulting in cold water being delivered to your faucets and circulating through your central heating system.

Because there are several possible explanations for this error number, you’ll need a registered Gas Safe engineer to visit your house to diagnose and remedy the issue.

gas fault

Why does the Vaillant boiler F28 error code happen?

The Vaillant boiler F28 fault code appears on the following Vaillant boilers and Vaillant models:

  • Vaillant ecoTEC
  • Pro ecoTEC Pro Plus
  • Turbomax Plus 824/828E

Check out our Vaillant Boilers Reviews: Are Vaillant Boilers any Good?

The F28 fault code is shown when your Vaillant boiler fails three ignition attempts, resulting in the boiler stopping and shutting off.

If you’re not sure how to do this, we recommend calling a Gas Safe registered engineer who can get your Vaillant boiler up and running again quickly and safely.

The Vaillant F28 error code is displayed when your Vaillant boiler fails three ignition attempts, resulting in the boiler halting operation and turning off.

The F28 fault code is officially defined by Vaillant as an “ignition fault”.

An ignition fault might be caused by a gas supply fault, a faulty electrode, or a damaged ignition, among other things.

A variety of issues could be causing this, including:

  • The control board has a short circuit.
  • Your compressor has a short circuit.
  • There is a short circuit or a malfunctioning fan motor, in the heat exchanger assembly

Vaillant instruction manual

“Failure during start-up: ignition unsuccessful – Gas meter is defective or gas pressure regulator has caused, the air in gas, gas flow pressure too low, thermal isolator device (TAE) has prompted, condensate duct blocked, incorrect gas restrictor, incorrect ET gas valve, fault on the gas valve,” according to the Vaillant installation manual.

Vaillant boiler F28 error code repair advice


A qualified Gas Safe Engineer would most likely investigate the following boiler components when determining the reasonableness of the Vaillant f28 error code on your Vaillant boiler:

Problems with gas supply to your other gas appliances

If you have a gas meter, make sure you are in credit, since this is a very typical scenario people encounter. Whether you have other appliances, such as a gas hob or a gas fire, check to see if they are operational to determine if you have a gas supply problem. If they do not work, you may need to contact your gas supplier.

When Are Gas Boilers Being Phased Out?

A gas supply issue is one of the most prevalent reasons behind a Vaillant f28 fault code.

You may simply test if this is the likely reason by turning on other gas appliances in your home and checking if they function.

If there is no gas supply, the fault code will be shown on the boiler until it is manually reset. This might be due to your energy company turning off your gas supply, infrastructure work in your region, or you just not topping up your gas meter (if you have one).

Do you want to pay for your new boiler on a monthly basis? Please see our Boilers on Finance guide.

Faulty gas valve

The major function of gas valves is to control the gas supply into the boiler, so that when there is a problem, no fuel may be burned to create hot water.

This image has an empty alt attribute; its file name is 1200px-Gas_Safe_Register.svg-1-910x1024-1-711x800-4.png

The Gas valve is the underlying cause of the F28 Vaillant error code, according to Gas Safe Engineers. The wiring harness to the gas valve and the gas valve operation are then investigated.

A faulty gas valve might be caused by an electrical or mechanical problem. Your engineer should relieve the gas valve if it is not fully worn out. If not, they’ll replace it with a new gas valve, which might cost up to £300. (usually including parts and labour).

Repair cost: £150-300

Faulty Wiring

For example, boiler components are electrically connected to the printed circuit board (PCB), which serves as the boiler’s control centre, controlling and coordinating the numerous boiler components.

A issue will emerge if a wire is poorly connected or if there is a wiring break. There might possibly be a problem with the ignition system (ignition cable, ignition electrode, ignition transformer, or ignition plug).

As a result, if a wire between the gas valve and the PCB becomes loose or detached, the signals will no longer be transferred, resulting in the gas valve malfunctioning and the boiler shutting down.

Repair cost: £100-500

Old boiler

It may be worth thinking whether you want to spend this kind of money on an old boiler (broken boiler) that is likely to break down again or show frequent fault codes. A new boiler with a longer guarantee and a higher efficiency rate that can save you money on your heating expenses.

Is your Vaillant boiler leaking or suffering from losing pressure? Use check out our fixed price boiler replacement guide.

Mechanical fault

Alternatively, the gas valve might be broken owing to a mechanical problem. The valve becomes prone to wear and tear over time, resulting in the valve sticking.

A gas valve that is prone to sticking will no longer be able to perform its duty – opening and closing whenever gas is required – reliably. As a result, the boiler may shut down and show the F28 fault code

Repair cost: £100-300

Electrode failure

When gas enters the boiler through the valve, it must be lit by the electrodes. If the electrodes become damaged, they will no longer be able to ignite the gas and generate the flame.

The electrodes can become worn over time and may need to be cleaned or changed, which trained Gas Safe Engineers can undertake.

Repair cost: £100-300

Frozen condensate pipe

frozen condensed pipe

The role of condensate pipes are to route poisonous flue exhaust toxic gases to the outside of your house, therefore when you have a condensate blockage, it may be a safety danger, which is why the boiler will immediately lock until the issue is remedied.

If the condensate line becomes clogged, the condensed flue gases cannot escape.

Condensate pipes have a tendency to freeze when there is any cold weather, resulting in a clogged condensate pipe. A Gas Safe Engineer can thaw the pipe and get the contents flowing again.

Fortunately, newer boilers, such as Worcester Bosch’s Greenstar Range, have CondenseSure, a function designed to keep your condensate pipe from freezing.

An inspection hatch in the flue may not directly prevent a frozen condensate pipe, but can indirectly contribute to minimizing the risk of freezing by facilitating servicing and inspection of the flue system. A well-maintained flue system ensures efficient operation of the boiler, which can help reduce the frequency of boiler shutdowns and subsequent condensate pipe freezing.

Repair cost: £50-100

Faulty PCB

The boiler’s processing unit is the printed circuit board, which is connected up and receives signals from several of the boiler’s components, managing their performance and ensuring they work together as intended.

faulty PCB

However, if you have the PCB incorrectly plugged in, you will be able to see a wire is loose or disconnected between a component and the PCB, or if the PCB is damaged, the boiler may shut down and show the f28 error number.

Repair cost: £100-500

HT Lead Is Broken

The lead that links the spark electrode to the boiler’s circuit board is also susceptible to breakage. Spark electrodes prevent the electrode from flaring, resulting in the boiler not igniting and creating an abundance of fault codes such as the F28 fault code

Repair cost: price varies due to boiler types

Other common Vaillant fault codes

The Standard Vaillant Boiler Warranty Protects:

The standard Vaillant warranty covers you for manufacturer-related issues or Vaillant defects, however, it stipulates that repairs must be performed by a service engineer hired or recommended by Vaillant. To keep your warranty valid, you must get your Vaillant boiler serviced on a regular basis.

Parts and labour are also covered by your warranty, which should be included in any boiler quotes you get.

Cost of Vaillant boiler service

A basic boiler servicing cost for Vaillant boilers is typically between £80 and £125, which is consistent across all types of boilers. There are additional factors that might influence the cost of your yearly servicing, one of which is where you live in the UK since hourly rates for engineers varies across the nation.

Fixed Price Boilers from Vaillant

If you want to learn more about how our fixed-price boiler quotation tool works, read our New Boiler Quotes Online guide and use our boiler size calculator.

Fill out the following form to receive Vaillant boiler quotes:

If your Vaillant boiler is showing the F28 fault code and you need it serviced, please contact us so that we can check into it for you.

Green Central avatar

Written by

Read some of our superb solar panel installation reviews from Trustpilot

Recently had solar panels fitted by Green Central and I can’t speak highly enough of the team. The whole experience has been trouble free and I would recommend them to anyone thinking about having solar panels installed – 10/10!

Rob Schofield


Our installation is now complete! 8 solar panels fitted and the journey from initial consultation through to the end product has been seamless.
Hats off Green central, Credit where it’s due.
Will definitely spread the word!



Recently had six solar panels fitted on my house by Green Central and I couldn’t have asked for a better service. In particular, I have to highlight the exceptional communications through out, the over all smooth running process and completely stress free experience, all down to Green Central. I now have grid independence which is valuable beyond estimation.


Name *
Email *
Phone No. *
Post Code *
Name *
Email *
Phone No. *
Post Code *