Combi boiler problem

Discussion in 'Plumbers' Talk' started by unphased, Feb 4, 2017.

  1. unphased

    unphased Screwfix Select

    My combi boiler was installed in May 2007 in the loft. Until recently (last six months or so) it has been trouble free but a fault has developed whereby at night time the boiler fires up and runs the heating for several minutes and then turns off. This then repeats throughout the small hours until morning. During the day it responds to the roomstat normally. Effectively, during the small hours it is overriding the temperature settings on the room stat. Last night I just had to turn the thing off and switch it back on this morning. I am thinking that this issue is related to colder temperatures in the loft space but what would cause the boiler to fire up and put the heating on overnight then behave itself during the day? My gas bill has increased dramatically this last quarter. What has changed in the last six months to cause it to do this?

    Glow worm 30Cxi.
     
  2. KIAB

    KIAB Well-Known Member

  3. unphased

    unphased Screwfix Select

    Thanks KIAB. This is a strong possibility, especially as the loft could be around 3 degrees or less overnight. Unfortunately there doesn't seem to be a way of making adjustments to those settings. Not sure how I can resolve this one? Should I put some tube heaters in maybe, with a stat control on those?
     
  4. KIAB

    KIAB Well-Known Member

    There is a way I reckon, but I don't do gas:(, need Dave or someone else.

    But, it might be always active on that boiler when boiler water temperature falls below 5- 8 degrees centigrade.

    QUOTE:

    The appliance has a built in frost protection device that protects the boiler
    from freezing. With the gas and electric supplies ON and irrespective of any room thermostat setting, the frost protection device will operate the pump when the temperature drops.
     
    Last edited: Feb 4, 2017
  5. unphased

    unphased Screwfix Select

    Ok mate, thank you. :)
     
  6. Mr Milliamp

    Mr Milliamp Member

    Could you build some sort of stud wall cupboard around it and thermally insulate it.
     
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  7. KIAB

    KIAB Well-Known Member

    Good idea.:)
     
    Mr Milliamp likes this.
  8. unphased

    unphased Screwfix Select

    Yes that is a good idea and it has crossed my mind. Thank you. ☺
     
    Mr Milliamp likes this.
  9. kiaora

    kiaora Well-Known Member

    Hi
    Don't worry , it's doing what it's designed to do.
    The boiler is designed to look after it's self.

    No need to change anything

    Its protecting itself

    Regards
    Peter
     
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  10. unphased

    unphased Screwfix Select

    Have had to resurrect this thread as my boiler has got far worse.

    Currently we can't shower. The hot water is only warm and it cycles warm/cold/warm/cold when showering. Also the CH is permanently on, now. The boiler won't respond to the room stat and doesn't respond to the dial setting on the front of the boiler, just keeps on firing and pumping water round the pipes.

    I am tempted to replace both flow and return thermistors?
     
  11. unphased

    unphased Screwfix Select

  12. terrymac

    terrymac Active Member

    Mornin unphased.is it just the shower or do all hot taps run hot /cold ? On a ten year old combi I would suspect a blocked plate HEX ,if all taps are same.
     
    KIAB likes this.
  13. KIAB

    KIAB Well-Known Member

    When you start wanting to spend that sort of money to repair a 10 year old boiler,then it's time to look for a new boiler, at least you could get up to a 5,7 warrenty.

    Is it only shower or other taps as well hot, water is only warm and it cycles warm/cold/warm/cold look at heat exchanger blocked.
     
  14. KIAB

    KIAB Well-Known Member

    Snap.

    Heat exchanger around £130 to replace.
     
    terrymac likes this.
  15. terrymac

    terrymac Active Member

    The boiler firing on CH when no demand is a separate issue.
     
  16. unphased

    unphased Screwfix Select

    Its all the taps as well. They run warm then start to get hot then go cold and its affected the shower the most. I have located a supplier than is clearing pumps the part no. is S801192 I can get it for £126.00. Could it be that? The reason I dont think its the heat exchanger is because the CH is permanently on so the pump diverter could be the fault?
     
  17. unphased

    unphased Screwfix Select

    What is the function of the heat exchanger and what is the function of the diverter pump? If it is a worsening of the problem in my opening post it would suggest that the pump could be the culprit if the CH is no longer controllable at all.
     
  18. KIAB

    KIAB Well-Known Member

    Possible

    Heat exchanger heat water for hot water, diveter valve switches between heating, hot water depending on call from heating or hot water,but it gives priority to your hot water.
     
  19. unphased

    unphased Screwfix Select

    I don't have new boiler money, Im afraid. Need to repair short term and look at new boiler long term.
     
  20. unphased

    unphased Screwfix Select

    KIAB do you think Its worth a punt at the pump? I need to go now as they close at 12 noon. Its in Newcastle under Lyme, about an hour from me.
     

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