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How to troubleshoot Worcester combi boilers

Worcester is now part of the Bosch Group. Which? members rate Worcester-Bosch as the most popular gas boiler brand, according to Worcester-Bosch themselves. However, sometimes their combi boilers develop problems. Finding out what the problem is -- and what to do to it -- requires a systematic check.

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First checks

  1. Follow the advice of Worcester-Bosch and check whether your combi boiler is displaying a fault code. This might be an EA code. Alternatively, it could be a D5 code.

  2. Find out what model combi boiler you have. Greenstar gas boilers and the 26 CDi model are prone to frozen condense trap or discharge pipe problems during cold weather.

  3. Check whether a blue light is flashing. If your combi boiler is a 26 CDi model, look for a flashing red light instead. If all of the above are true, try to reset your boiler.


  1. Locate the reset button. This is on the boiler control panel. Press the button firmly.

  2. Hold the button in. Wait ten seconds. Release the button.

  3. Wait a few minutes. The boiler should reignite. If it does, you have reached a successful outcome to the troubleshooting process.

Further checks and actions

  1. Listen for a gurgling noise if your boiler does not fire up. This probably indicates a frozen condense. Check your condense pipe next.

  2. Check whether the pipe is less than 32 mm in diameter. See whether it is insulated with waterproof lagging. If not, the pipe could be frozen.

  3. Contact your installer to thaw the pipe. Alternatively, place a hot water bottle against the pipe. However, you should only do this if the pipe is at ground level. It is important not to attempt to thaw a pipe at any other height.

  4. Reset the boiler using the method above when the pipe has thawed. If this advice does not work or your combi boiler has a different problem, contact Worcester-Bosch customer services (see Resources).

  5. Warning

    Exercise great caution when endeavouring to thaw your condense pipe. Worcester-Bosch recommends you get a Worcester Accredited Installer to do the job.

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Things You'll Need

  • Ruler
  • Hot water bottle

About the Author

Frank Luger had his first educational resources published in the early 1990s. He worked on a major reading system for Cambridge University Press, became an information-technology adviser and authored interactive whiteboard resources for "The Guardian." Luger studied English literature and holds a Bachelor of Education honors degree from Leeds University.

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