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When the temperature drops during the winter season, the water in the condensate pipe may freeze if it terminates outside. If this happens, it is most likely that your boiler will fail to start, meaning no heating or hot water.
In this guide, we'll walk you through the meaning of the F28 code and provide detailed steps on what to do next so your gas boiler can return to providing your home warmth.
If you've noticed your heating has not come on when expected and your boiler displays an F28 code, it means there could be an ignition error.
The official explanation for an F28 fault is "The flame signal was not detected during the ignition phase," which can be caused by several different factors, such as a frozen condensate pipe, which you can fix yourself.
You’ll typically find your condensate pipe exiting at the nearest outside wall from your boiler. It often appears as a small, PVC-U white pipe starting from the wall and leading down into a drain or run-off system. Sometimes, condensate pipes connect directly to wastewater flows, like the waste pipe of a sink.
However, an F28 can also mean a more technical issue, which will require the help of your installer or support from Vaillant.
If you suspect your condensate pipe is frozen, there are some simple steps that you can take to defrost it without having to call an engineer.
If you see an F28 code on the boiler display screen, or you hear a bubbling and gurgling sound coming from your boiler whilst in use.
Note that pipes are more likely to freeze if your boiler and heating system have not been in consistent use during a period of freezing temperatures. This often happens when you leave your home for a holiday and do not use your boiler. We advise keeping your boiler active on a schedule timer to avoid pipes freezing.
To defrost a condensate pipe, pour warm water along the affected area of the pipe to dislodge, melt and remove the ice blockage.
Use a suitable container - like a watering can or pitcher - and continue the process until either the ice falls from the pipe or until the contents of the pipe are fully drained.
Do not use boiling water from a kettle, as this can damage or crack the pipe, causing damage that will be costly to repair and render your boiler non-functioning for the duration.
Check your boiler manual for instructions on how to reset your boiler correctly before undertaking this operation, then restart your boiler.
You can avoid having to repeat this process in future by insulating your condensate pipe. By insulating your condensate pipe you are reducing the risk of it freezing and blocking again in future.
If you see an F28 code on the boiler display screen, or you hear a bubbling and gurgling sound coming from your boiler whilst in use.
Note that pipes are more likely to freeze if your boiler and heating system have not been in consistent use during a period of freezing temperatures. This often happens when you leave your home for a holiday and do not use your boiler. We advise keeping your boiler active on a schedule timer to avoid pipes freezing.
To defrost a condensate pipe, pour warm water along the affected area of the pipe to dislodge, melt and remove the ice blockage.
Use a suitable container - like a watering can or pitcher - and continue the process until either the ice falls from the pipe or until the contents of the pipe are fully drained.
Do not use boiling water from a kettle, as this can damage or crack the pipe, causing damage that will be costly to repair and render your boiler non-functioning for the duration.
Check your boiler manual for instructions on how to reset your boiler correctly before undertaking this operation, then restart your boiler.
You can avoid having to repeat this process in future by insulating your condensate pipe. By insulating your condensate pipe you are reducing the risk of it freezing and blocking again in future.
Once your condensate pipe is thawed, insulate it to prevent future freezing. Pipe insulation, available at DIY stores, is easy to fit.
Make sure the pipe is fully defrosted before you measure the pipe, cut the insulation to size and fit it around the exposed pipe. If freezing persists, contact a Vaillant installer.
If the issue is not related to your condensate pipe, you may require support from an expert. This can be related to the gas supply, an electrical fault or an ignition issue which cannot be resolved by yourself.
Find your local Vaillant installer.
Similar to an F28, an F29 error means your boiler flame went out. In freezing weather, it could be a frozen condensate pipe. If it's not cold and you're on a pre-payment meter, check if you have credit. If your gas is on and working, it's time to call a professional.
The official list of Vaillant boiler fault codes is available only from us. You’ll find it on our overview page, and we keep it constantly updated to ensure you have the latest information.
Our service contracts help prevent many heating system faults. Our experts monitor your system, fine-tune the settings, and proactively reach out when maintenance is due. This keeps your heating running smoothly and efficiently for the long term. Plus, with the myVAILLANT app, you can check and optimise your system’s performance anytime, right from your smartphone.
