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New CH/DHW System choices

Discussion in 'Plumbing and Central Heating' started by DoctorJohn, 25 May 2010.

  1. DoctorJohn

    DoctorJohn

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    Big question
    I have an old 3-bed but quite large terraced house, one (only) bathroom upstairs, front right, with the kitchen as far away as it's possible to get at the rear left, in an extension. The current open-vent system is Oooooold. Museum-piece but reliable Kingfisher CF60 in the kitchen, only fails when the draw through the 22' flue dies in cold calm weather (I'm serious) and the pilot light snuffs out. There's an ancient tank in the under-stairs cupboard. With a tortuous 14m pipe run to the bathroom (a good deal of which I think is 22mm) and 7m to the kitchen. The hot water flow rates are so poor that I open the bath tap when I get out of the (electric) shower so that by the time I'm dry there's hot water for a shave. Boiler output just about (surprisingly) OK as house was fine this winter.

    There's stacks of room in the loft, where I could arrange a compromise spot for the new boiler/tank, and that would give about 10m pipe to the bath and 12 m to the kitchen. I can easily get the gas up there, and with a flat roof the flue exit isn't a problem.

    I'm resistant to the idea of a combi having hated them in previous houses, I really resent the cycling every time you open the hot tap (yes, there's lots of messy hot water on/off stuff in the kitchen, no dishwasher!).

    Requirements:
    1: mains pressure DHW
    2: Acceptable lag from tap opening to hot water coming out
    3: facility to ditch electric shower and install one using DHW system

    So my questions are:

    Is the length of pipe runs I've mentioned OK/Typical/sensible
    (10m of 15mm holds 1.5 litres or thereby?) enough to make the compromise tank location work for bath and kitchen?

    Would anyone recommend thermal store against an un-vented cylinder

    Should I give up the compromise attempt and optimise the Bathroom/CH with a combi, and just put a separate instant water heater in for the kitchen?

    Thanks in advance

    J
     
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  3. Agile

    Agile

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    The simple answer is a small new boiler and an unvented cylinder sized for the number of people who live there and usually never less than 210 li.

    Then you have a HW pumped loop to the kitchen and to the bathroom then you will get immediate HW.

    Those pipes should all be lagged and ideally the pump should be on a time switch AND on a thermostat so it.

    Tony
     
  4. DoctorJohn

    DoctorJohn

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    Thanks for the tip. Hadn't thought of that as an option. I googled for pumped DHW circuit info and found some interesting stuff on the Grundfoss site. Made me think: with the loo at the end of the line, I could just feed the cistern through a suitable thermostatic blending valve (i.e 15 - 25 C range), and the simple act of flushing the loo in the morning would then draw enough hot through the pipe to get the result I want. It would also have the advantage of putting room temp water in the cistern, hence reducing the condensation problem you get with mains fed cisterns.
     
  5. Agile

    Agile

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    I think your mind is drifting beyond what would be considered normal!

    Tony
     
  6. Razor900

    Razor900

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    Tony, Tony - It takes one to know one you know ;)
     
  7. Andygasman2010

    Andygasman2010

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    Imagine having a hot toilet!!!!! Amazing ;) haha

    Stick with a seconday pump and loop :)
     
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    DIYnot Local

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