Viessmann f2 fault code

What does the Viessmann F2 fault mean?

F2 is the fault code that indicates the Viessmann boiler’s burner has “locked out”, which prevents it from producing the flame that burns fuel. In a gas boiler, this stops the hot water from heating up when you need it.

One of the more common Viessmann boiler problems, this code is usually not caused by the burner. Most often with this lockout, it is a problem with the circulation of a gas boiler or burner blockage.

Viessmann F2 error code & faulty central heating system pump

The main cause of this Viessmann fault code will be the pump which is the component that circulates the hot water through the central heating system properly.

Once the water has traveled through your heating system, it will re-enter the unit via the return pipe.

This can cause hot water to stop flowing from the boiler at the right speed. If it isn’t possible, the unit could overheat.

It is important to avoid this as it can cause severe damage to the internal parts of your boiler, which could be costly and can prevent it from working completely.

When the boiler’s Printed Circuit Board(PCB) detects that a component is not working properly, a fault code will be displayed.

The PCB is responsible for receiving signals at each stage of the heating process. This confirms that it has occurred before the next step can be taken.

It will shut down the boiler to stop unsafe functioning if it detects that the pump is not working or there are other issues.

What Causes the Viessmann F2 Fault in

Heating Sludge Blockage

Heating sludge can cause circulation problems in a Viessmann Boiler and central heating system as it can build up in pipes and pumps and the dreaded heat exchanger.

It is a thick mixture formed when rust and dirt are removed from pipes as water flows through them.

If enough of these small bits of debris are present in the water they can congeal to form a sludge that travels slowly through pipes. It can eventually lead to total or partial blockage.

It can block the shaft and bearings that allow the part spin freely if it reaches the pump. This can cause intermittent operation or even a complete stoppage of the pump.

In the event of a Heating Sludge Blockage

A Viessmann boiler engineer might take a sample of water to determine if there is a heating sludge obstruction if it is not obvious from a visual inspection.

Whatever the case, once the sludge is identified, they need to flush it out using a process called a system flush.

It involves the use of specialist chemicals to clear your heating system by removing blockages.

This service is usually more expensive than expected depending on how large the heating system is. However, a rough estimate of cost would be between £400 and £500, with a £100 increase per radiator.

If you have a Viessmann combi boiler, the sludge that has built up around the pump can be removed without the need for a new one. If the pump has sustained damage, however, it may need to be replaced completely.

This part’s cost will vary depending on the type of boiler or generic pump you use. Prices range from £100 to £250.

Your engineer might recommend fitting a magnetic filter to your boiler if it doesn’t have one.

They prevent limescale and sludge buildup by catching particles of debris before they can stick together. This is a great way for heating systems to last longer.

They are usually less expensive than £100 and can be cleaned every time your boiler is serviced.

Pump Air lock

Pumps can become stuck if too much air is trapped. This will stop the pump from spinning as it needs to.

The system is able to take in air in small quantities as water flows into it, but larger amounts when certain works, such as drainage, are done.

This issue is often characterized by knocking sounds from the pump or a decrease in pressure. You can check the gauge on your boiler’s front for these signs.

The units of pressure are called bars. A recommended reading is between 1 to 1.5 bars.

What to do if there is an airlock in the pump

The process of removing air from the pump is known as “venting” or ‘bleeding”, and the tool that is used to do this is called a ‘bleed screw.

This tool allows an engineer to remove the cover plate, allowing air to escape. Water will then start to trickle out. The boiler can then be reset and the pump can be re-fitted.

This is an easy and inexpensive repair job, provided there aren’t any other problems with the boiler. Sometimes, the boiler can be damaged if it is left running for too long. In these cases, replacement or repairs may be necessary.

Codes such as F2 can be used to prevent boiler damage.

Incorrectly Installed pump

First, the pump should be facing in the correct direction to allow water to flow. This is a common problem in newer installations.

Modern pumps can have multiple speed settings, so the incorrect setting may have been used when it was installed.

This problem is often apparent shortly after the pump has been installed. However, it can also occur when heating is required more frequently during colder periods.

What if there was an incorrect Installation of the Pump

It’s worth calling an installer before calling an engineer if you have recently installed a boiler. They will be able check the pump fitting and adjust it if necessary.

It is easy to change the speed. This will not require costly repairs.

No Power to Pump

Alteration or loose wiring could have caused the pump to lose its function. This is usually due to vibrations in the boiler, many which are caused by the pump.

This connection is essential in order for the PCB to signal the pump to turn on or recognize that it is running.

What do if there is no pump power?

Sometimes loose wiring can be identified by visual inspection. Engineers can use a tool called the multimeter to measure the resistance of electrical components.

This will identify any areas that are not connected to power and can be replaced or reconnected as necessary. The cost of wiring is not expensive. However, the labor time needed to diagnose and repair the problem will affect the final price.

It is often more cost-effective to replace the pump if it has stopped working completely. Although repairs may be possible, once the faults start, they are more likely to reoccur. A replacement is usually cheaper than a repeat repair.

An engineer might recommend a Grundfos pump instead of a Viessmann component since these parts are cheaper but just as reliable.

How can I fix my own Viessmann boiler with the F2 fault?

Because they are behind the boiler’s covers, most of these faults will require a registered Gas Safe engineer for diagnosis and repair.

If your pressure gauge has dropped below 1 bar, it is safe to reset the boiler and repressurise the boiler to check if that works.

Boilers will lose pressure over time, so they will need to be repressurized once a year. This doesn’t necessarily indicate that there is an issue.

These steps will help you repressurise the boiler.

  • Make sure the boiler is turned off and that the unit has cooled.
  • You will find the filling loop under the unit. Both ends should be secured securely with no water leakage.
  • If you don’t have one, an external filling loop will be required.
  • Each of the small handles should be turned to the open position, in line with the pipe.
  • Once the pressure reaches 1.5 bar, you can return to closed position
  • After the boiler has been turned back on, check the pressure again

How to Repair a Viessmann F2 Fault code

A Gas Safe registered engineer will be able to perform these fixes on a Viessmann boiler as above as unless you are qualified it is illegal for you to do so. A call out could easily solve these problems and it may just be a quick repair. However if you have an old inefficient boiler and this Viessmann fault code keeps showing up, then it may be time to invest in a new boiler.

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