Worcester Bosch boiler overheating.

Discussion in 'Plumbers' Talk' started by Dj_barb, Nov 8, 2019.

  1. Dj_barb

    Dj_barb New Member

    I have a Worcester Bosch Green Star 34 CDI Classic.

    The boiler is 11 months old. (Still in warranty).

    Recently I have been experiencing some strange things happening with our DHW.

    Every morning when I run a hot tap / shower I just get cold water. When I go to the boiler it displays a very high temperature of 114 and isn't firing. The boiler is located on the first floor and the pipes that run under the first floor under the floor boards bang and make lots of noise.

    If I continue to run the hot tap / shower the boiler will eventually cool down to 50 Deg and then eventually fire. This can take 10-15 mins.

    The water that comes out initially once it has fired will be kettling then returns to normal DHW temperature within 30 seconds.

    The DHW will then continue to run perfectly throughout the day untill the next morning when the same problem occurs. It's almost as if something is happening during the night as the system rests.

    This has all just started like clockwork as soon as we switched on the heating last month.

    I have had a Worcester Bosch engineer out and he identified the problem as a faulty PCB as it controls a variable speed fan (his words). Unfortunately this hasn't fixed the problem.

    I'm not a heating engineer but I am starting to go out of my mind as I can no longer rely on my recent 11 month old investment to have a hot shower before work each morning. The time it takes for the boiler to cool down each morning is getting longer by the day, so maybe getting worse?

    Any help, tips or advice would be greatfuly received.
     
  2. just pumps

    just pumps Screwfix Select

    No.1 Try and stay within your mind snowflake
    No.2 It`s under warranty so call them back
     
  3. andy48

    andy48 Screwfix Select

    1. Check the boiler temperature before you run the hot water first thing in the morning.
    2. If it has already overheated, then:
    2a. The chances are the problem lies in the central heating, not the hot water circuit.
    2b. Look for a blockage in the central heating, like a valve being shut or something similar.
    2c. If you have a filter installed on the return pipe to the boiler, make sure any valves are open. (NOT any valve used to empty the filter).
    2d. Make sure the valves which isolate the flow and return pipes (the thick (22 mm)) pipes under the boiler are open.

    I'd check 2. above first. If you call Vaillant out, and it is not a fault with the boiler, they may charge you for the visit.
     
  4. just pumps

    just pumps Screwfix Select

    It's not a Vaillant Andy.
    Not that makes much difference of course
     
  5. andy48

    andy48 Screwfix Select

    Oh dear, shouldn't post late at night should I?
     

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