Loft Conversion impacting on HW decisions - HELP!!

Discussion in 'Plumbing and Central Heating' started by Crakkers, 27 Jun 2018.

  1. Crakkers

    Crakkers

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    Hi

    We currently have a system boiler that was installed in 2007 with an open vent cylinder in the loft.

    We are having a loft conversion.

    So originally thought about a closed vent cylinder to feed hw system linked to existing boiler.

    Some plumbers now advising on replacing a perfectly working boiler with a combi and doing away with all tanks etc in the loft. This does sound appealing to have no extra bits to worry about, but increases the expense.

    As someone who has shied away from combis believing they cant power a decent shower or fill a bath before the water gets cold, I am being told my thinking is a little out of date.

    If go for a combi, what make and model?

    When complete, we will have 1 bathroom with bath and shower, plus a shower room in the loft. 3 people live in the house.

    Whats your advice?

    Thanks in advance..
     
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  3. muggles

    muggles

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    If you're expecting to run two showers at once, a combi probably isn't for you. Having said that, you need to know your incoming mains flow rate & pressure before any decision can be made. You can't get out more than you have coming in (at least, not without some shenanigans) so if your incoming mains performance isn't sufficient to run an unvented cylinder, a combi may still be appropriate.
     
  4. dilalio

    dilalio

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    It's the same old story... Headroom in the loft originally meant for water, is now a Bedroom in the loft for people :).

    Stay at home kids into their 20's (or 30's :sick:) means average 3 bed semis are busting at the seams... Including my own... 3 kids very quickly becoming 3 adults!

    I went for a combi, a decent one with as good hot water flow rates as I could get, with a very good mains pressure and flow thankfully, because, quite simply, space is more important to us than jet washing in the showers! We can still get adequately showered simultaneously with the added bonus of a luxurious shower when it's the only one in use... Which is usually the case as individual schedules have naturally developed to ensure such :D

    Adapt and overcome.
     
  5. MeldrewsMate

    MeldrewsMate

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    I'm not a natural combi fan, but they have their uses, especially where space is at a premium. Leaving aside the arguments about single hot water outlet at once, they 'wear out' their electronics faster than the conventional (regular or system) boiler by virtue of the fact that every time a hot water outlet is used the boiler goes through its ignition cycle. There is also the argument that the combi must have an adequate gas supply, sometimes requiring an increase in gas pipe size. If in a hard water area (most of Lancs is relatively soft, I think), then adequate water treatment should be budgetted for to prevent rapid loss of performance due to heat exchanger scaling.

    A pressurised hot water cylinder must have an adequate water supply to give of its best, sometimes requiring an increase in mains water pipe sizing, though this is easily determined at the planning stage. Just as for a combi, the output water rate is set by the rate at which water can get in to it, however you can keep your existing boiler, and it has the added advantage of having an alternative method of heating the water should the boiler break down, the immersion heater. Another advantage is that a pressurised cylinder can make use of a secondary hot water circulator, reducing the delay getting hot water to a distant outlet, the best example being that of a combi in the loft feeding a kitchen hot tap or a downstairs bathroom - long waits for hot water delivery. Often I see grossly oversized cylinders installed in houses, in spite of freely available advice from manufacturers and the heating and hot water trade bodies. Typically, for a house with a bath and two showers, the guidance is 120 to 150 litres, with reheating times as low as 20 minutes for a decent brand.

    If you have the space for an unvented cylinder,and the mains water supply is adequate, I would go for that over a combi conversion.
     
  6. Keithmac

    Keithmac

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    We had poor water pressure and flow, so our combi suffered from that (no fault of the boiler).

    After fitting a Homeboost to up the flow our combi can fill a bath in 10 minutes which is fast enough for us.

    As has been said, your water supply flow rate and pressure (not static) should be measured before you decide what to do next..
     
  7. If there is sufficient incoming cold mains flow & pressure available in the loft,fit an unvented cylinder in same position. The loft converter plumber can check flow & pressure rates.
    A larger pipe upgrade of the incoming cold water main may be required for an unvented cylinder but still better than a combi or pumping.
    That :cautious: usually includes a shower/en suite,so extra hot & cold water demand.

    best not to compromise on the plumbing :idea:
     
  8. DIYnot Local

    DIYnot Local

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