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Hot water temperature setting when using a Combi Boiler

Discussion in 'Plumbing and Central Heating' started by Juliesm, 6 Apr 2020.

  1. Juliesm

    Juliesm

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    I have a Combi boiler. I'm wondering: what's the lowest temperature that I can set the supply to taps at please?

    I don't have mixer taps in the house and really don't want 60C hot water coming out of the taps.
     
    Last edited: 6 Apr 2020
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  3. ianmcd

    ianmcd

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    you wont get 60 C with a combi, the way a combi works is that faster the water flows through the boiler the colder the tap temp will be, the faster you run the tap the colder the water will be , the slower you run the tap the hotter it will be , but the boiler wont let you have 60C water temperature , you are mistaking system boilers where the water has to be stored at that temp to prevent legionella
     
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  4. Juliesm

    Juliesm

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    Hmm. Thank you for your answer. Now then, if I understand you correctly, the temperature I set at the boiler, will not have a positive or negative effect on the growth of legionella in my pipes.
     
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  5. Madrab

    Madrab

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    Ideal temp at the outlet is 50 - 55deg.

    The water in a cylinder is held @ >60deg, to minimise legionnaire bacteria as it's stored water, that temeratur usually drops to 55deg or lower by the time it gets to the outlet.

    Yours, as it's a combi, isn't really affected by the legionnella issue as it's mains, instantaneous, hot water and isn't stored long enough for the bacteria to multiply enough to become a problem. The worst case and as I always recommend to clients, if you are away for 2+ weeks then always run your hot and cold water until it's fully hot/cold to evacuate any water that has sat in the pipes for any length of time. Only issue you may have is if you have any long unused sections of pipework (dead legs).

    Same goes for anyone that has lead pipes, always run it every day for a min to clear out any water that was standing in the pipes overnight.
     
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  6. ianmcd

    ianmcd

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    no you are not storing HW with a combi, you heat it as you need it and you wont get 60C out of your tap
     
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  7. Juliesm

    Juliesm

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    Thanks Madrab Your answer is exactly what I thought. My landlord, housing association, stipulates that the tap water temperature at the boiler should be set at 60C. I usually have it at 42C so that I don't burn my hands. I can't figure out why they say to keep it at 60C, since as you so rightly pointed out "it's mains water".
     
  8. Madrab

    Madrab

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    They'll be using it as a coverall to cover their ass if there were any subsequent problems. As suggested, that approach is for stored hot water.
     
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  9. Juliesm

    Juliesm

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    Thank you Madrab
     
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  11. hard-work

    hard-work

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    That is wrong, an old wives tale. A well specced combi will deliver 60C for sure.
     
    Last edited: 7 Apr 2020
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  12. Juliesm

    Juliesm

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    Thanks hard-work. In my experience, the longer I leave the tap running the hotter the water gets. That's why I have mine set at 42C.
     
  13. hard-work

    hard-work

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    They are ignorant. They have been told/read that stored water is to be stored at a min of 60C. They do not know the difference between instant or stored water. Typical.
     
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  14. Juliesm

    Juliesm

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    Thanks Madrab, I think, they also have older properties which may still have a water cylinder and or an overhead tank. So maybe they are just saying 60C to everyone in order to keep the people living in those properties safe.
     
  15. JohnD

    JohnD

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    What temperature is the incoming water? You forgot to say.

    How many litres per minute is it delivering? You forgot to say.

    All three figures are related.
     
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  16. ianmcd

    ianmcd

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    Really please tell me one that will , I am actually a boiler engineer when you are not , cant wait till you tell me what combi boiler will give 60 C at a tap outlet really sorry @Juliesm that you have been involved in this but Hard work is just that he is not any kind of tredesman and is just an internet troll
     
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  17. hard-work

    hard-work

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    The implication was that a combi could never deliver 60C, which is nonsense. I wrote, A well specced combi.
     
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