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Heat only Vs System boiler Vs Combi (running costs)

Discussion in 'Plumbing and Central Heating' started by boolie, 24 May 2021.

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Which uses the least amount of gas and electricity?

  1. Vented cylinder with heat only boiler

    4 vote(s)
    57.1%
  2. Unvented cylinder with System boiler

    2 vote(s)
    28.6%
  3. Combi boiler

    3 vote(s)
    42.9%
  4. Heat only with unvented

    1 vote(s)
    14.3%
Multiple votes are allowed.
  1. bernardgreen

    bernardgreen

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    I do have that minor problem as the cold water tank has to be in the bathroom. ( Very high ceiling and joists attached the rafters so not intended for any load ) bearing
     
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  3. vulcancontinental

    vulcancontinental

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    At between 3.5 and 5p/kW cost of NG is very cheap.

    BRE did research some years ago, available online as I found it, where the end result was a heat only boiler was the most efficient in operation over a combination boiler but the losses between the boiler and cylinder cancelled that out.

    The distance between boiler and cylinder is also a factor as is the distance between the combi or cylinder and the hot tap used most often (a reason I personally don't think a combi in the loft is a great idea).

    Use a low mass boiler for rapid heat up, aluminum if you're running radiators hot and intermittently and consider stainless if the system is going to be running at condensing temperatures for long periods.
     
  4. Mottie

    Mottie

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    My mate has a combi boiler in his loft and rather than waiting for the hot water to get to the kitchen tap, they boil a kettle of water to do the washing up!
     
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  5. vulcancontinental

    vulcancontinental

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    roughly 4p/kW compared to 16p/kW, if it works for them fine but the OP wanted to understand running costs.
     
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  7. shambolic

    shambolic

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    I have a SS combi running an unvented cylinder with draw offs to all hot taps apart from my en suite which comes off the combi for the constant 20l/min shower. the heating is under floor with oversized rads upstairs to run at 55deg.
    Has outside weather comp and opentherm internal controls. Hw priority that heats cylinder before opentherm/weather comp kicks in for heating requirements.
     
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  8. DavidLewis

    DavidLewis

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    That sounds ideal. For reference, what combination of boiler / controls manufacturers (and models) do you use to achieve your setup please?
     
  9. shambolic

    shambolic

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    Tbh you’d need to research your own application as mine was specifically designed for my own house when building it. the spec is now 5/6 years old and things have came on and got better even from then.
    But basically 3 zone system one of them being hot water. Other 2 zones are rads and then 12 manifold under floor heating.
    mu controls are a mix and match as it was that I could use at the time but there are now plug and play stuff with online controls etc that might suit your needs better.
     
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  10. boolie

    boolie

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    sounds like the rolls royce of heating systems.. way above my pay grade. A system like that you're probably talking at least £10K all in

    Would love to see pics of your boiler room
     
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