Error f28 on Vaillant Boilers


How to fix error F28 in a Vaillant boiler in a few easy steps

Error F28 in a Vaillant boiler is a safety feature in the unit. It is essentially a misfire but it can have various causes, from a gas supply failure to broken wiring. The main characteristic of error F28 in a Vaillant boiler is that it is a fault that can cause your boiler to completely stop working until you have corrected the problem. In this article, we will discuss the causes of error F28 in a Vaillant boiler and their corresponding solutions.

Vaillant Boiler error code F28: What does this mean?

When error code F28 is displayed on a Vaillant boiler, it means that the unit has been locked. After 3 unsuccessful ignition attempts, the boiler goes into error status and should display error code F28, which according to the user manual is an ignition fault. This start-up error can, however, be due to various causes: insufficient gas supply, failure in the ignition circuit (electrodes, HT cable, electronic card), or it might be that the gas has combined with air. Let’s take a look at the causes and solutions in more detail.

First step: restart or reboot the boiler

The most basic solution for boiler users is to restart or reboot the boiler. This can get the unit up and running normally again. The maximum number of restart attempts should always be less than 5. If you haven’t been able to restart the boiler after that number of attempts, it’s best to contact a technician to check your boiler and help you to start it up again. They will be able to what has caused the error and what the best solutions are.


Regulator problems

The gas regulator is another component that can get blocked or become faulty, thereby preventing the movement of the gas supply. It can either be completely or only partially blocked. Check that your gas regulator is operating properly and, if not, it might need to be replaced.

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Fuel supply problems

One of the most common causes of error F28 in Vaillant boilers is insufficient fuel supply. If it is a gas boiler, it is sometimes difficult to tell if there is enough fuel or not, especially if the fuel doesn’t come from a gas cylinder. If you have a shared gas supply, you may need to check other gas-powered appliances (such as gas stoves) to see if there is a supply.

You can also use a water column meter to check for gas. Finally, you could also contact your gas company to check if there is a general gas supply problem or if they are carrying out any work that could be causing gas supply interruptions.


Check if the gas supply valve is open

Something that is quite simple, which can appear trivial but is not, is that the boiler’s gas supply valve may have been accidentally closed. According to how gas supply valves are designed, the tap should be perpendicular to the tube. When it is open, it should be aligned with the tube.

Defective or faulty gas valve

The gas valve may also be problematic. A faulty gas valve normally has its own error code (F62), but because it can cause ignition problems, it should also be one of the parts that should be checked when trying to fix this problem.

Error code F28 in the Vaillant Ecotec Plus boiler is often caused by a faulty gas valve. It is normally best to replace this with a new part.

The electronics card is faulty

If the boiler is making strange sounds (it can sometimes be quite noisy), this may be a sign that of an ignition problem, and error code F28 may be caused by a faulty electronics card. In this case, you might need to replace it with a new part.

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Check your gas meter

If you are lucky enough to have a gas meter at home, you should also check if there is a general gas supply problem. If there is no problem with your meter and there is gas, the amount should be displayed on the boiler with pressure bars. However, if your boiler seems to be switching on but the gas meter doesn’t move, the problem would then obviously not be due to insufficient gas supply but due to another problem.

Dirty, faulty, or misaligned electrodes

Another cause of error F28 in Vaillant boilers is electrode failure. In this case, the solution would be to check if the electrodes are dirty, faulty, or misaligned. If they are dirty, you should clean them. If they are misaligned, they should be realigned (it is advisable to consult the user manual for the correct measurements). If they are damaged, you would need to replace them with new ones.

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The HT cable is broken

The HT cable forms the connection between the electrode that creates a spark to start the combustion flame and the boiler’s electronics board (also known as the PCB). This cable can break, thereby preventing the electrode from generating a spark which, in turn, causes the boiler not to start and results in error code F28. You should check if this cable is broken and, if so, replace it.

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