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Is your Viessmann boiler showing the F2 fault code? We're here to help you understand what it means and guide you on how to fix it. This article explains the F2 fault code and its possible causes and offers expert advice on how to resolve it. Always consult a Gas Safe registered heating engineer to fix boiler issues safely and professionally.

What Does Viessmann F2 Fault Code Mean?

An F2 fault means your burner is locked out, so there's no flame to heat the water. This results in no central heating or hot water.

Simply, the F2 fault code on Viessmann boilers indicates a problem with the central heating pump or a blockage. This issue needs a professional touch from a Gas Safe registered heating engineer to sort out.

Although it might seem like the problem is with the burner, it often stems from a circulation issue with the pump. The pump moves the heated water through your home via the flow pipe. After circulating, the water returns to the boiler through the return pipe.

If the pump isn't working properly, the heated water stays in the system instead of circulating. This may result in boiler overheating and damaging the boiler's internal parts, leading to more inconvenience and expensive repairs.

The Printed Circuit Board (PCB) monitors the system to prevent damage. It acts as a checkpoint, ensuring each step is safely completed before moving to the next. If the PCB detects a circulation problem or a pump failure, it locks out the boiler, triggering the F2 fault code.

Why Do Error Codes Matter?

They help identify issues quickly, making it easier to keep your heating system running smoothly. Therefore, error codes are essential for modern boilers.

Boiler error codes play a crucial role in the smooth operation and maintenance of modern boilers. They act as important diagnostic tools that identify issues within the system.

When homeowners encounter an F2 boiler fault code on a Viessmann boiler, it can be both inconvenient and concerning. This error code means a burner lockout, which stops the burner from heating water.

Is Viessmann F2 Fault a Serious One?


The fault can arise from various causes, such as a lack of gas supply or more complex issues like electronic component failures. Understanding what an error code indicates is essential to take the right steps toward fixing it.

The F2 fault code indicates that the boiler's safety parameters have detected a potential risk and have shut down the burner.

Homeowners can perform some troubleshooting steps, like checking for obstructions or resetting the boiler, but it's often necessary to seek help from a qualified engineer.

Depending on the nature of the underlying problem, the difficulty and cost of fixing an F2 fault on a Viessmann boiler might vary. In some cases, it may require significant boiler repairs or even replacement.

What Should You Do?

If you see the F2 fault on your Viessmann boiler, don't panic. We will explain the F2 boiler fault, its possible causes, and how to fix it. Always get the advice of a professional Gas Safe registered engineer to handle boiler problems safely and professionally.

Common Causes of the F2 Viessmann Fault

The F2 fault code on your Viessmann boiler may be due to various reasons.


Here are some common culprits:


A buildup of sludge, dirt, rust, or limescale can cause blockages in your heating system.

Sludge, a dense mixture of debris, rust, and dirt, is a prevalent problem with many boilers.

It gathers in the system, obstructing pipes and other components and disrupting water circulation.

As sludge accumulates, it can obstruct the pump shaft or bearings, impeding their movement. When the crucial parts of the pump are unable to move freely, the pump ceases to function.

Pump Airlocks

Trapped air in the pump can disrupt the water flow in the heating system. This can happen naturally as water circulates or if air enters large amounts during work, such as drainage. When air gets trapped, it can cause the pump to stop working.

If you've noticed a drop in pressure or loud humming noises, there might be an airlock in the system. Check the pressure gauge to see if it reads 1-1.5 bar, which is the recommended level.

Ventilation Issues

Lack of adequate air intake due to poor ventilation or a blocked flue can affect combustion.

Pump Problems

Incorrect installation or malfunctioning pumps can hinder water circulation. If your boiler isn't functioning after a recent service or installation, it could be due to incorrect pump installation. The boiler won't operate until the pump is correctly aligned for water circulation.

Another potential issue could be the pump's speed setting. Modern pumps offer various speed options, and if it's set incorrectly, the pump won't function properly. While this problem is often identifiable, sometimes the low-speed settings are only noticed during winter months.

A faulty pump prevents the proper circulation of heated water in the house, leading to boiler overheating and triggering the Viessmann F2 fault code.
Extreme Weather

Freezing of the condensate pipe during cold weather can lead to system failure.

Wear and Tear

Debris accumulation and worn-out parts may result in issues like flame loss or overheating, triggering the F2 fault code.

To resolve an F2 error, identify these potential issues and seek assistance from a qualified professional for safe and effective solutions.

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Common Signs and Symptoms of F2 Boiler Fault

  • Unusual Noises: When your boiler is running, pay attention to strange sounds like grinding or humming. These noises could signal issues with internal parts, such as the pump.
  • Decreased Hot Water Pressure: If the water flow from your taps weakens, it might be a sign of the F2 error. Low hot water pressure indicates a problem in the heating system that is affecting its regular operation.
  • Unevenly Heated Radiators: Cold radiators alongside hot ones or slow heating can indicate circulation inconsistencies linked to the F2 boiler fault.
  • Boiler Pressure Fluctuations: Keep an eye on the pressure gauge; erratic needle movements suggest pressure instability often tied to the F2 Viessmann fault code.
  • Temperature Inconsistencies: Problems in temperature control or circulation can trigger the F2 code. Heating irregularities can range from no hot water to insufficient heating performance.

Spotting these signs early can prevent a complete boiler shutdown, ensuring continuous and effective heating and hot water provision. Regular servicing is advised to maintain the boiler's optimal condition and effectively troubleshoot these symptoms.

Easy Ways to Fix f2 Fault on Viessmann Boiler

  • Resetting: Start by pressing the reset button under the boiler cover. Wait for it to restart.
  • Check Wiring: If resetting doesn't work, look at the wiring using a multimeter. Make sure you know what you're doing with electricity.
  • Repressurise: Low pressure might cause the error. Check your boiler manual to add more pressure if needed.
  • Thaw Pipes: In cold weather, pipes can freeze. Warm them up gently to fix the issue. Insulate them to prevent future freezing.
  • Be Careful: You can check and adjust some things yourself, but don't mess with anything too complicated. Opening the boiler without proper qualifications is risky and against the law.

Viessmann Warranty and Support

Viessmann boilers usually have a warranty covering specific parts and labour for a set period. The kind and any active promotions may affect how long the warranty lasts.

Remember to register your boiler post-installation to activate the Viessmann warranty.

If you encounter issues like the F2 fault code or other boiler problems, feel free to contact Viessmann's customer support for guidance and assistance. They can assist you in troubleshooting, provide details on warranty coverage, and refer you to a nearby Gas heating engineer if needed.

When to Get Help

A professional might be needed if the problem continues after trying these fixes. Stop and get help if you suspect a gas leak. Only Gas Safe engineers should deal with serious problems like burner faults.

In summary, it's okay to try simple DIY fixes if you are familiar with your boiler settings, but for safety and legal reasons, leave the big stuff to the professionals.

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How To Reduce Boiler Pressure?

If your boiler's pressure drops below 1 bar, you can top up the system to troubleshoot without calling in a professional.

  • To top up your boiler:
  • Shut down the boiler and let it cool.
  • Locate the filling loop under the boiler. Check for secure connections and no leaks.
  • Open the small valves on the filling loop to increase the pressure.
  • Close the valves when the pressure hits 1.5 bar.
  • Turn the boiler back on, ensuring the pressure stabilises.

Following these steps might fix the issue and sidestep costly repairs or professional help.

If Your Heating System Is Blocked By Sludge

In such a situation, your boiler engineer may need to test the water to confirm the issue, especially if it's not clear. Once they identify the sludge, they'll flush it out using a special process called system powerflush, which uses specific chemicals to clear the system and remove blockages.

Depending on how big your heating system is, this servicing may cost different amounts. Typically, it ranges from £400 to £900, with an extra £100 for each radiator.

For Viessmann combi boilers, removing sludge around the pump is usually possible without replacing it. However, if the pump is damaged, it might need replacement, which can cost between £100 and £300, depending on your boiler or pump type.

Your engineer may recommend adding a magnetic filter to your boiler if it doesn't have one. These filters help prevent limescale and sludge buildup by catching debris particles before they cause issues. They are usually affordable, costing less than £100, and can be cleaned during your boiler's regular service to extend your heating system's longevity.

What Can Affect The Boiler Repair Cost?

Firstly, warranty coverage plays a significant role, as repairs may be partially or fully covered under the boiler's warranty. The complexity and compatibility of the central heating system with the boiler can also impact costs.

Older or discontinued boiler models may be more expensive to repair due to the difficulty in sourcing parts. Additionally, the efficiency of the fix can influence initial costs, with more efficient solutions potentially being more cost-effective in the long term. Plumbing requirements, such as extensive work, can also increase costs. It's essential to hire certified technicians for boiler repairs to ensure safety and efficiency. Homeowners should consider these factors and may want to invest in annual boiler servicing to prevent such issues.

Don't forget to register your boiler after installation to activate the warranty. If you need guidance or assistance, feel free to contact Viessmann's customer support.

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