Condensing boiler tips

Keep your condensing boiler working through winter

High-efficiency gas boilers are good for your home and your pocket as they extract more energy from the gas being burned to generate heating and hot water.

Winter can bring problems for them, however, as condensing boilers can sometimes shut down if their condensate pipes freeze – leaving your home without heating when you need it most.

Why they can freeze

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

During the combustion process, the boiler produces a water vapour that’s cooled to leave waste water ‘condensate’. This condensate is disposed of through your home’s waste water system.

The outlet pipe for the condensate may have been fitted outside your home if there wasn’t room for it inside. If so, cold temperatures can freeze the condensate in the pipe and this can cause a blockage that will shut your boiler down.

How to tell if it's frozen

Your boiler’s operating manual will tell you what signs to look for. Usually, there will be a fault code on the boiler’s display or an alarm will sound. Your first sign might be that you have no hot water or heating though.

What you can do if it's frozen

If you feel confident and safe enough to do so, you can do the following to thaw your pipes and free the blockage:

  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 – turn off your water at the mains and thaw the pipe out slowly using using a hot water bottle close to the blockage (don’t pour boiling water directly onto the pipe)
  3. Restart your boiler – follow the instructions in your boiler’s manual to do this

How to stop it from freezing

There are a few steps you can take to help prevent your condensate pipe from freezing up in cold weather:

  • Insulate your condensate pipe with weather-proof insulation to help protect it from the cold
  • Leave your heating on overnight at a lower temperature to keep the condensate warm. Although this uses more energy, your boiler will take less time to heat up your home in the morning
  • Set your boiler thermostat to a higher temperature to reduce the amount of condensate created. This will use more energy and is only recommended if you have radiators rather than underfloor heating. Be careful when doing this as your 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.

Gas boiler and central heating protection, including an annual boiler service, is available with Home Emergency Response from the AA.

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