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Last updated: 12th February, 2024


Vaillant F28 Error Code - How to Fix?

Vaillant F28 Error Code - How to Fix?

Key takeaways

  • The Vaillant F28 error code indicates a boiler has an ignition or gas valve problem.
  • F28 causes can include: gas valve mechanical fault, frozen condensate pipe blockage, electrical wiring fault or low boiler pressure.
  • Use a fully trained, Gas Safe registered engineer for any F28 repairs.

Any time your boiler displays an error code, it can be a huge stressor, especially if it degrades the performance of your heating system, ESPECIALLY in the freezing, winter period!

In this blog we’re going to be exploring the pesky F28 error code for Vaillant boilers, including what this means, what’s the cause and the best way to solve the problem.

Error Codes Explained

A boiler error code displays an alphanumeric three digit fault detection message (e.g. F28) when the system detects an error such as an integrated component not functioning as it should.

Error codes are found on the boiler's digital display screen, located front and centre on the unit itself or at the bottom of the casing, sometimes covered by a plastic folding panel.

Vaillant F28 Meaning

Officially, the Vaillant F28 code signals an ignition fault, this problem can be complex due to the fact it can be caused by several internal issues, The F28 warning code will be emitted if the boiler fails three ignition attempts.

The broad list of potential causes mean the F28 can be, in a wider sense, categorised as a gas valve issue as well as an ignition problem.

Ignition is required to light the gas, creating the flame which heats the cold water that runs over it, thereby providing the property with a supply of hot running water; a gas valve controls the flow of gas within the boiler.

An F28 error code can result in a boiler ‘lockout’ (shutdown to prevent further fault). We understand the desire to get your central heating system up and running by simply restarting your boiler, but just hang on if possible!

Carrying out assessments and diagnosing the cause of the issue can be hugely beneficial in the long run and can enable the issue to be completely remedied, rather than half fixed, potentially leading to further breakdowns.

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F28 Causes

Mechanical Fault With The Gas Valve

The valve, which opens and closes to meet the boiler's gas demands, may begin to stick over time due to natural wear and tear, especially if the boiler is an older model, impairing overall heating functionality.

Frozen Condensate Pipe Causing A Blockage

A condensate pipe transfers ‘condensate’ or wastewater by-products, from a boiler to the outside of a property, usually depositing it in a sewage system.

A condensate pipe may become blocked or obstructed due to cold weather causing the pipe to freeze, this can negatively impact a boiler's performance when you need heat the most.

How To Thaw Out A Frozen Condensate Pipe

The most common way to thaw out a frozen part of the condensate pipe, is to pour warm water over the outside of the piping, but be careful as not to cause a slip hazard. Also don't pour boiling water on the pipe, let this cool down for 10 minutes first.

Alternatively, you can place a hot water bottle on the affected area or have the above ground part of the piping lagged (insulated).

Electrical (Wiring) Fault

Boiler components are connected electronically to the PCB (printed circuit board), this is the control centre responsible for regulating the coordination of several integrated components.

If any wiring or circuitry is poorly connected between the gas valve and PCB, the signals will no longer be effectively transmitted, resulting in valve malfunction and a boiler ‘lockout’.

Low Boiler pressure

Low boiler pressure could be caused by several occurrences such as:

  • Water leak in key pipework area

  • Pressure relief valve that has been left open

  • Radiators been inefficiently bled

  • Not enough water entering system 

  • Broken or condemned boiler

If your boiler is suffering from low pressure, check out our handy troubleshooting guide!

Fixing The F28 Error Code

The issues discussed above that may be the potential cause of the F28, can be complex heating issues that if improperly handled could lead to further boiler problems or health risks.

It’s always wise to organise an expert, Gas Safe registered engineer to undertake any substantial boiler work!

Gas Safe Registered Engineer

This is a fully trained and qualified gas engineer who is legally licensed under the published Gas Safety (Installation and Use) Regulations 1998 (GSIUR).

The Gas Safe Register is the appointed representative of the safety regulatory group- Health and Safety Executive. All of our iHeat engineers are registered Gas Safe!

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Arranging for your boiler to be annually checked over or ‘serviced’ by a qualified engineer can be a fantastic way of analysing the state of your heating system in yearly increments, identifying and rectifying any faults before they have a chance to progress.

Be Proactive With iHeat

The best way of ensuring your boiler is operating as it should, is by proactively replacing ageing or faulty boilers at the earliest signs of degradation, this preventative step is far more prudent than reactive maintenance.

It’s a mechanical and engineering fact that due to some of the technological advancements in recent times, modern boilers are more robust and efficient than anything made previously. 

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Frequently Asked Questions

How do I fix the F28 error code on Vaillant boiler?

To fix the F28 error code on a Vaillant boiler, it is recommended to call a Gas Safe registered engineer. They can diagnose the problem and repair any ignition or gas valve problems. Do not attempt to repair the boiler yourself, as this could be dangerous.

What is the cause of the F28 fault on a Vaillant boiler?

The F28 fault code on a Vaillant boiler indicates an ignition or gas valve problem. Common causes include a mechanical fault with the gas valve, a frozen condensate pipe blockage, an electrical wiring fault, or low boiler pressure.

How can I clear an F28 error code on my Vaillant boiler?

It is crucial to address the underlying issue causing the F28 error code before clearing it. A Gas Safe registered engineer should be called to diagnose and resolve the problem. Once the issue has been fixed, the engineer can reset the error code.

Is the F29 fault code related to F28 on Vaillant boilers?

Yes, the F29 fault code is related to the F28 error code on Vaillant boilers. Both codes indicate problems with the boiler's ignition process. While F28 refers to a failure during start-up, F29 signifies flame loss during operation, which can also result from issues with the gas valve or wiring.

What is the difference between F28 and F54 fault codes on Vaillant boilers?

The F28 fault code indicates an ignition or gas valve issue, while the F54 fault code signifies a problem with the gas pressure sensor. Although both codes involve gas-related issues, the F54 code is specifically related to the sensor that monitors the boiler's gas pressure.

How does cold weather influence the F28 error code on Vaillant boilers?

Cold weather can cause the condensate pipe to freeze and block, leading to the F28 error code. Insulating the pipe can help prevent freezing in cold conditions. If the pipe is frozen, gently thaw it with warm water or a hot water bottle and ensure it is insulated to avoid reoccurrence.

What steps can be taken to fix the F28 error on Vaillant Ecofit Pure?

To fix the F28 error on a Vaillant Ecofit Pure boiler, check if the gas supply is turned on and ensure the prepayment gas meter has enough credit. If the problem persists, it is recommended to call a Gas Safe registered engineer to diagnose and fix any issues related to ignition or gas valves. Always hire a professional to handle gas-related repairs for your safety.

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Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.