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Condensing boiler tips

Keep your boiler working through the winter

The good news is that a high-efficiency gas boiler is good for your home and your pocket. It extracts more energy from the gas being burned to generate heat and hot water.

But freezing winter weather can bring problems for condensing boilers. They can sometimes shut down if the condensate pipe freezes, leaving your home without heating just when you need it most. Here's what to do.

Condensing boiler tips

Why the condensate pipe can freeze

Condensing or 'condensate' boilers work in a similar way to conventional gas boilers, but use energy more efficiently by reusing heat from the flue gases to heat additional water.

During this process the boiler produces left-over water vapour that cools to leave 'condensate'. This condensate is disposed of through your home's waste water system.

The outlet pipe for the condensate may be outside your home if there's no room for it inside. If so, cold temperatures can freeze the condensate in the pipe and cause a blockage. And this can shut your boiler down.

Usually, there'll be a fault code on the boiler's display or an alarm will sound. (Your boiler's operating manual will explain the fault code.) But the most obvious sign may be that you have no hot water or heating.

How to prevent your condensate pipe from freezing

  • Cover your external condensate pipe with foam pipe insulation.
  • Leave your heating on overnight at a lower temperature to keep the condensate warm. Although this uses energy, your boiler will take less time to heat up your home in the morning.
  • Set your boiler thermostat to a higher temperature. This will use more energy and so reduce the amount of condensate. Only do this if you have radiators rather than underfloor heating. Be careful – the radiators will get very hot.

If you do change any heating settings, remember to return them to normal once the cold spell is over.

These steps may not prevent freezing in extreme weather conditions. If you want to take further action, detailed guidance will be available from your installer or service engineer.

What can I do if it does freeze?

If you feel confident and safe enough, try to thaw your pipe:

  1. Locate the blockage – it's likely to be at the most exposed external point, or at a bend or dip in the pipe.
  2. Thaw the frozen pipe – use a hot water bottle close to the blockage (don't pour boiling water directly on to the pipe).
  3. Restart your boiler – follow the instructions in your boiler's manual.

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