Vaillant Fault Code. What Does it Mean?

Vaillant Fault Code

Vaillant high efficient boilers are now one of the most popular boilers being installed today.

Like any boiler though, they have to be maintained annually to keep them working to their full potential.

So when you get a Vaillant fault code suddenly appear on the boiler display, what should you do?

Reading the manual that came with the boiler, you will see many explanations of a Vaillant fault code,

these are only a guide though, the idea is to try and point you in the right direction of the fault.

Sometimes it’s a quick fix to clear the Vaillant fault code, just by pushing the reset button, but not all the time.

The most common Vaillant fault code is F22, this is then followed by F75.

If you see either of these 2 fault codes appears on the boiler screen, it’s to do with water pressure loss.

Check the gauge on the boiler, what does it read, if it’s on zero, the boiler needs topping up.

You can add pressure by opening the filling loop, normally located just under the boiler, some models have 2 grey taps directly below.

Looking at the taps they will say closed, By opening them you will hear water entering the boiler.
Make sure you close both these taps when finished topping up.

When topping up the water pressure take your time, don’t overpressure the boiler, you are looking at around 1.2 to1.5 bar of pressure.

Too much pressure, the boiler may discharge once the boiler starts heating up, taking it back to zero.

If you are not sure on how to top up your boiler pressure,

I would advise you to call in a Gas Safe Registered Engineer, not a Plumber, a registered boiler engineer.

The F75 Vaillant fault code means that the water pressure sensor has not detected an increase in pressure.

When the boiler fires up, the pump starts to move water through the boiler, this increases the internal pressure,

the sensor picks this up, if it cannot sense the increase of pressure, F75 will display on the screen.

If the boiler pressure is ok, and you can hear the pump running, you will need to replace the water pressure sensor.

These tend to get blocked up with sludge.

A good way to prevent this is by having an inline filter fitted to the return pipe of the boiler.

Now let’s look at another Vaillant fault code that pops up when you need your boiler most F27.

I know this may sound strange but, today’s high efficient boilers don’t like the cold. If you see F27 in the display, you may have a blocked or frozen condense pipe.

When the boiler is working it produces condense, if it cannot discharge it backs up into the heat exchanger, F27 displays and the boiler goes to lockout. Sometimes it may even display F28.

The condense pipe is plastic, it removes the condense and discharges it into a drain.

Many condense pipes discharge to an outside drain, this pipe needs to be protected from the cold weather.

This is most common Vaillant fault code in the winter months, so make sure your condense pipe is protected.

There are many fault codes but these are the most common ones that will make your boiler go to lockout.

Your boiler is a very important part of your home, don’t neglect it, maintain it and it should keep you warm when you need it most.