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Best Temp setting on a combi

Discussion in 'Plumbing and Central Heating' started by Londoner2, 29 Oct 2020.

  1. Londoner2

    Londoner2

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    Its that time of year again when we talk about getting the best performance out of your combi.

    Ignoring everything else what is the best temp setting for:

    1) Condensing Efficiency:
    2) Economy:

    Thanks.
     
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  3. ericmark

    ericmark

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    I would think it would vary? If we look at the whole concept of using a modulating wall thermostat using some thing like OpenTherm the idea is to have circulating water as cool as it can be, and still warm the home to the required amount. The whole idea is until the point where the boiler can't turn down any more, or there is a change in the requirements, the boiler does not turn off.

    With my oil boiler that is not modulating then it is a good question, again no real answer, too low and reheat time is increased, to high and the domestic hot water is too hot.

    So once I am permitted to go out, the idea is while out, the wall thermostat detects no movement in the house, and it see the phones are not in the house, so it switches the heating down or off. And when it detects my immanent return it starts to raise the room home temperature again, how fast it can re-heat the home depends on boiler output, boiler output temperature and radiator sizes.

    I know that the boiler never seems to run for more than an hour, so it seems likely the combined radiator sizes are not enough to transfer all the energy from the boiler into the house, so lifting the temperature would allow a faster reheat of house, but then the temperature of the radiators could damage items that touch them or are need to them, and the DHW would be hotter, so boiler temperature remains half way.

    If a motorised valve was fitted to the water heating the DHW then maybe I could raise the circulating water temperature, but that means installing more cables over three floors, and told not good for boiler.

    So if home always occupied then the lower the temperature likely the better, but if heating is turned off/on as you leave the home and return, then it is the reheat time. When the flame out has locked out the boiler, it takes a long time before we realise it is not working, the home cools really slowly, so unless we left the house for a holiday, in the winter, I don't think we will ever find out how long it takes to heat from scratch.
     
  4. ianmcd

    ianmcd

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    What ever you are most comfortable with
     
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  5. I think the whole condensing= economical thing is over rated.Economy...as said...as cool as you are comfy with/ or can afford maybe.
     
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  6. Londoner2

    Londoner2

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    I appreciate everyone's opinions but i just need the industry standard settings on what it should be set to.
     
  7. bernardgreen

    bernardgreen

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    Surprised that no one has mentioned that boilers only "condense" when the water entering the boiler (*) is below dew point temperature.

    With regards to boilers, dew point is important as it allows the heat exchanger to work at its most efficient; the condensing of the water vapour releases additional energy into the heating system. The dew point of the byproducts created when burning natural gas is around 55 ℃.

    (
    *) water returning from radiators and/or coils in hot water cylinders and/or cold water feed to combi boilers
     
  8. Londoner2

    Londoner2

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    Ahh, ive heard about 55c before, one engineer did mention that before.
     
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