combi boiler help….. please!

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  • combi boiler help….. please!
  • Greybeard

    The shower symptoms suggest the mixer may be faulty. I had a faulty shower mixer that allowed cross-flow between hot and cold, even when in the off position, so as soon as I turn off the hot tap, cold water backfed into the boiler. Don’t immediately see how that could cause your boiler symptoms but worth checking out – once your system is not working as designed lots of weird things can happen! Fixed by putting non-return valves in the the pipes to the shower (replacing the shower will be done sometime but is a big job as the pipes in the wall are non-standard).


    Rift in time-space continuam


    not sure how it trips out on the hot tap as the temperature is controlled to 58 ish degrees iirc from mine.

    I suspect the two are separate faults and mixer sounds like a good one.


    hi out there,

    i have a Bosch Worcester greenstar combi boiler I have a couple of problems with:

    When I run the hot tap in the bathroom the boiler works fine for 3 -4 mins then trips out, restart and repeat. It only does this with this ONE hot tap in the house.

    Recently when having a shower the hot water has become very twitchy ie it’s either scalding hot or freezing cold, all within about 5 mm rotation of the shower mixer.

    both faults are in the bathroom which is at the same level as the boiler. Don’t know if that makes a difference but thought it might be relevant.

    any thoughts anyone? (preferably folk with some plumbing heating knowledge!)


    Could be a faulty flow rate sensor . Lowish flow = very hot water , sensor then tells boiler tap/shower is off ( when it isnt ) and turns off heat. Water still runs but goes cold.
    See if you can recreate this by popping the cover and running a hot tap in the bathroom.
    The boiler will fire , and you will see flames, get your assistant to slowly turn down the flow rate. Shout when flames go out , if tap is still running then you have a problem somewhere.


    thanks all single track mind sounds the mot likely as the shower is only a year old. However I am inclined to agree with dales rider and blame a rift in the space time continuum.
    thanks all will investigate


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