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Thread: Combi or Conventional boiler

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    Question Combi or Conventional boiler



    Have no idea with plumbing, so just wondering if people have any recommendation which type to go for. Basically we have just moved into a 30 years old house and the boiler (of the same age) needs replacing.

    Quite a few plumbers have recommended combi, but I have friends & relatives who have had bad experience with these.

    A bit of background info, it's to be used in a detached house for a family of 2 adults and 3 kids!

    Thanks in advance!

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    Re: Combi or Conventional boiler

    Personally, I don't like combi's ..... but there are reasons why it works better for some people.

    My view is that it all revolves round the idea of not having a hot water tank. The downside of a tank is that you heat water in it and, if you don't use it, it slowly goes cold so you've wasted the energy (and cost of) you used to heat it.

    However, my answer to that is :-

    1) A properly insulated hot water tank
    2) Our lifestyles are such that we heat water, briefly, morning and evening and, as the tank has a thermostat on it, ONLY if the temp has dropped.

    So, any losses from water cooling are minimal.

    A major advantage of a combi is that you don't need that hot water tank. So, you save the space it would take and, if installing a new system, the cost of buying and installing that tank ..... or of replacing it when it eventually fails.

    But, the wife informed me that she was NOT losing the nice warm tank in her airing cupboard, so just forget it, alright!

    Also, from what I've read, if you have two or more bathrooms, not having a tank can cause flow rate issues.

    So, while I'm sure there are times and people for whom a combi works, it doesn't appeal to me at all. But I'm not a plumber or heating engineer, so there may be other good reasons for them that I've missed.

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    Re: Combi or Conventional boiler

    advantages of combi:
    space/energy saving as no separate hot water tank required
    mains pressure hot water (although you can get this with an unvented system on a non-combi)
    usually cheaper/easier overall for a new complete system install

    disadvantages:
    because no hot water tank there is usually a small period of time (~20 secs) before hot water flow reaches required temp. (there are a few combis with a small integrated hot water storage tank to overcome this).
    if it fails/shuts down you lose both heating & hot water (separate hot water tanks usually have an immersion heater as a backup).
    Because it can only add a finite amount of heat in the given time & because water inlet temp in Winter is noticeably colder than in Summer hot water temp/flow rates in Winter aren't as good as in Summer.

    2 adults & 3 children but how many things likely to require hot water at same time as that's probably what will govern your boiler sizing rather than heating output?

    I've had a Worcester HiFlow storage combi for ~20 years & I'll shortly be replacing it with an updated model (the improved efficiency & hence fuel cost saving will pay for the boiler over ~ 8 years).

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    Re: Combi or Conventional boiler

    Thank you both for the advise.

    One of my main concern is that we usually shower after dinner, problem that I have experienced with a combi boiler is that if someone is washing up downstairs, whoever shower upstairs will either get a blast of cold or hot water inconsistently, hence I have never been a fan of the combi bolier.

    We have a conventional heating system now, so not sure how much saving would I have with a combi, the cost difference to install either, and not have the 'shower-wash up' problem .

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    Re: Combi or Conventional boiler

    Quote Originally Posted by eden188 View Post
    One of my main concern is that we usually shower after dinner, problem that I have experienced with a combi boiler is that if someone is washing up downstairs, whoever shower upstairs will either get a blast of cold or hot water inconsistently, hence I have never been a fan of the combi bolier.
    that's really a system design problem -with a properly sized boiler & appropriate piping it should be possible to do both

    We have a conventional heating system now, so not sure how much saving would I have with a combi, the cost difference to install either, and not have the 'shower-wash up' problem .
    Given that you have an existing system then a conventional boiler probably makes more sense unless you either want to release the space taken up by your existing hot/cold water tanks or you want mains pressure hot water .

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    Re: Combi or Conventional boiler

    Quote Originally Posted by eden188 View Post
    One of my main concern is that we usually shower after dinner
    Messy eaters?

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    Re: Combi or Conventional boiler

    You got me. I laughed out loud at that one. I guess my sense of humour is stuck in my schooldays.

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    Re: Combi or Conventional boiler



    Hehehe!! Nice Schmunk, btw, the 2 adults and 3 kids, I'm one of the kid .

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    Re: Combi or Conventional boiler

    we had combi boiler in last flat but we also had hotwater tank not sure how that worked mind but we did

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    Re: Combi or Conventional boiler

    Go for a combi -german one if possible very efficent.

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    Re: Combi or Conventional boiler

    I have a honeywell combi boiler at home and it works extremely well.

    The hot water doesn't get "hot" until about 20 seconds of running but once it's hot you can run it all day if needed

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    Re: Combi or Conventional boiler

    Quote Originally Posted by Saracen View Post
    But, the wife informed me that she was NOT losing the nice warm tank in her airing cupboard, so just forget it, alright!

    Also, from what I've read, if you have two or more bathrooms, not having a tank can cause flow rate issues.
    No need to lose out on the airing cupboard. Take out hot water tank, put in a small rad, and in winter you will have no issues drying cloths in there, plus you get more room. Its what i had done to mine when i changed over to a combi and its been one of the best moves i've done so far.

    Yes there can be flow rate problems, but they can be sorted out. Making sure the boiler is set up right, if you still have issues (like a workmate had) add a pressure regulator into the system (again takes a little bit of setting up) and its sorted.

    Not sure, but i thought new house builds come with combi's as standard now?

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    Re: Combi or Conventional boiler

    Thank you all for the suggestions/advice. It looks like it will be fine to have a combi boiler afterall. My next question is does £2200 looks reasonable to fit this in (plumber said this is for a top combi boiler), remember, I'm in Manchester, so everything is cheaper up here

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    Re: Combi or Conventional boiler

    True enough about the rad in the airing cupboard, beanbandit, but it does mean taking out the tank and then paying to install the rad. IIRC, it would also have involved other pipework as the heating circuit and HW circuits are very different here.

    Quote Originally Posted by eden188 View Post
    Thank you all for the suggestions/advice. It looks like it will be fine to have a combi boiler afterall. My next question is does £2200 looks reasonable to fit this in (plumber said this is for a top combi boiler), remember, I'm in Manchester, so everything is cheaper up here
    My boiler replacement, a bit under a year ago, cost £5k. But, due to building regs I was no longer allowed to have the boiler in the purpose-built boiler room.

    It had to be moved, and that was about a day and a half of plumbing and electrical work, which was half, ore a bit over half, the cost. Ours wasn't a combi, but £2200 doesn't sound wildly unreasonable, depending on exactly what boiler it is, and on exactly what work has to be done.

    Oh, and in my case, the boiler having to move has an upside. I now have a 'purpose-built' server room. Of course, that isn't the purpose it was built for, but hey .... not too many '60s homes had server rooms designed into them.

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    Re: Combi or Conventional boiler

    another benefit is you dont run out of hot water. Two flats I have lived in both new builds, didnt
    have enough water in the tank for two decent showers and i am not talking long showers.

    Really though a power shower is better you dont have to worry about pressure and temp changes

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    Re: Combi or Conventional boiler

    Kumagoro,

    If I'm right, you are saying combi never runs out of hot water?

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