Main Multipoint BF burner cuts out during shower

Discussion in 'Plumbers' Talk' started by mogwai101, Aug 4, 2013.

  1. mogwai101

    mogwai101 New Member

    Our multipoint BF burner cuts out durign a shower....so we had it serviced and....it still cuts out.  After about half a min the temperature comes back up for a couple of mins and we repeat the cycle.
    The boiler is about three years old.  The tap on the bath is a thermostatically controlled mixer....which I just replaced thinking it may be the cause......but the problem persists.
    Any advice greatfully received.
     
  2. tom.plum

    tom.plum Screwfix Select

    will the service engineer not come back, it seems to me he has a responibilty, he took your money and did't improve things, I'd say its one of three things, a faulty diaphram , the overheat stat or the heat exchangers furred up,
    a diaphrams about £10, a overheat stat's £30 and the heat ex is a couple of hundred quid,

    So if he won't come back start with the cheapest and work your way up.
     
  3. mogwai101

    mogwai101 New Member

    Thanks for the response.
    I am confident that it is not a furred up heat exchanger as we have a well functioning water softener.
    The cut out only seems to happen on the shower....perhaps it is that we turn of the tap before it cuts out on the otehr circuits.
    I will order a diaphragm, but I thought it would not work atall if that was faulty....then we will try the overheat stat.
    Thanks for the advice.
     
  4. tom.plum

    tom.plum Screwfix Select

    well I've known a diapham to give imtermitant hot water, but it would do it at all the taps, so its more likely to be the overheat stat, but it won't do any harm to fit a diaphram anyway, just another consideration, I know you've fitted a new shower, is it fitted with the cold on the right? the cold must be on the right or you'd get this trouble,
     
  5. tom.plum

    tom.plum Screwfix Select

    p.s a water softener won't stop a hex furring up, if it is the heat ex, you'll hear a noise like a kettle boiling as it gets hotter,
     
  6. mogwai101

    mogwai101 New Member

    It is connected with the hot on the left facing the unit (as it has been for a long while).  I just swapped it over and the boiler did not fire what ever th setting of the thermostat....so I guess the pipework is OK.  I will start have a look at the diaphragm tomorrow.
    No noises coming from the heat exhanger..just the sound of the burner and the water rnning through.
    Where can I get a diaphragm and overheat stat at the prices you suggest?
     
  7. tom.plum

    tom.plum Screwfix Select

    keeptheheaton.com or a local partscenter. most plumb center's have a partscenter dept,

    both those parts are non gas, so they should supply them to you,
     
  8. mogwai101

    mogwai101 New Member

    Many thank.
    I called Keeptheheaton.com
    A very helpful gent said he did not have the parts I needed but passed me on to GasAppliance Spares hwho have the parts..they are on the way (less than£40for parts, shipping and VAT).  Partcenter had a price of £103+vat for the diaphragm!!!
    I will hope to finish the story on Wed when I install the parts.
    Thanks so much for the advice and great source for parts.
     
  9. tom.plum

    tom.plum Screwfix Select

    can't understand part center wanting £103 for a diaphram :eek: he must have got the wrong part number or priced for the whole valve, anyrode hope that sorts it,
     
  10. IT is scaled up
     
  11. mogwai101

    mogwai101 New Member

    Here is an update on the problem.
    I purchased the overheat thermostat and the diaphram and opened the case to fit them.......
    Could not see how to fit the diaphragm without removing parts from the gas side of the system (so I now have a spare diaphragm).  I replaced the thermostat and tested the system......no change.
    I put it back together and cranked the heating rate to the higest setting ........and it works!

    I do not think that scale is a problem.  We have a water softener that was fitted prior to the installation of the heater.  The softener should  (if working correctly) cause a net removal of scale from a system (see the report referenced in the link http://www.harveywatersofteners.co.uk/blog/the-science-behind-the-benefits

    I am confident it is working properly.  The previous heater (chaffauteaux Brittony TII) required me to remove the heat exchanger (HEX) every couple of years and remove Kgs of scale..or replace the HEX.
    Thanks for the continued interest.
     

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