1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

New Combi or Unvented Cylinder?

Discussion in 'Plumbing and Central Heating' started by EddyP, 12 Aug 2015.

  1. EddyP

    EddyP

    Joined:
    7 Feb 2008
    Messages:
    160
    Thanks Received:
    0
    Country:
    United Kingdom
    Evening all,

    We've currently got a 15 year old Worcester Oil Heatslave 18/25 Combi, it's working fine but we're about to replace the kitchen and in order to make the kitchen work properly we either need to move the boiler by about 12" or fit a smaller one.
    So I'm thinking that if we're moving it we might as well replace it at the same time as it must be towards the end of its life now.

    But then I was thinking, we have an airing cupboard very close to the location of the existing boiler, so would it be worth considering to put in a system/regular boiler and an unvented cylinder instead?

    The mains water pressure here is really good, too much intact as I had to fit a pressure reducing valve.

    Showers off the current combo are fine, there's only two of us in a 5 bed house currently so no issue with showers running at the same time but in the future when kids are about it could be more likely.
    At my last house I fitted a Valiant 837 and that managed to cope with two showers just about so am wondering if we stick with a combi and put a big one in then two showers might be OK?

    The house has one bath, and three showers.

    There's no way we can have solar as the house is listed so no benefit to having a solar loop in the cylinder. The electric might be useful if we ever run out of oil though.


    Any thoughts or advice?


    Thanks
     
  2. Sponsored Links
  3. wannocks

    wannocks

    Joined:
    8 Nov 2008
    Messages:
    1,216
    Thanks Received:
    315
    Country:
    United Kingdom
    Combis can struggle to provide for more than one outlet I would go with unvented.
     
  4. flameport

    flameport

    Joined:
    10 Mar 2007
    Messages:
    9,927
    Thanks Received:
    1,989
    Location:
    Poole, Dorset
    Country:
    United Kingdom
    More than one bathroom = Cylinder.
    A combi will do one outlet reasonably well. Might perhaps give two feeble showers, but only as long as no other hot water is used anywhere. Only needs someone to use the hot tap in the kitchen and it will be totally useless.
     
  5. muggles

    muggles

    Joined:
    28 Oct 2005
    Messages:
    13,341
    Thanks Received:
    3,076
    Location:
    Daventry
    Country:
    United Kingdom
    Definitely heat only boiler and UV cylinder needed here. You'll save a lot of space by changing the boiler as well - a new heat-only should be around 350mm wide
     
  6. bernardgreen

    bernardgreen

    Joined:
    3 Nov 2006
    Messages:
    25,827
    Thanks Received:
    2,572
    Location:
    Bedfordshire
    Country:
    United Kingdom
    Muggles is correct. Heat only though a vented cylinder would be a bit less hassle than un-vented ( my personal opinion )

    Heat only boilers have far less inside them so can be much slimmer than an "equivalent" combi.

    A slim line combi can be a real pig to service as all the bits are crammed together and if there is a fault then maybe half the boiler has to be dismantled just to get to the fault if the faulty item is at the back of of the boiler
     
  7. Dan Robinson

    Dan Robinson

    Joined:
    1 Jul 2007
    Messages:
    56,034
    Thanks Received:
    9,420
    Location:
    Hertfordshire & London
    Country:
    United Kingdom
    You don't half talk some crap. :LOL:

    I do however agree a combi in this case is suboptimal.
     
  8. EddyP

    EddyP

    Joined:
    7 Feb 2008
    Messages:
    160
    Thanks Received:
    0
    Country:
    United Kingdom
    Thanks guys that really helps.

    Presume a system boiler has two circuits one for DHW and one for CH where as a regular is a single circuit that you use with a 3 way valve?
     
  9. Dan Robinson

    Dan Robinson

    Joined:
    1 Jul 2007
    Messages:
    56,034
    Thanks Received:
    9,420
    Location:
    Hertfordshire & London
    Country:
    United Kingdom
    No.

    It has a pump in it.
     
  10. Sponsored Links
  11. bernardgreen

    bernardgreen

    Joined:
    3 Nov 2006
    Messages:
    25,827
    Thanks Received:
    2,572
    Location:
    Bedfordshire
    Country:
    United Kingdom
    Are you saying a combi is as easy to service as a heat only boiler. ? One of the early combi's had the pump fitted at the back of the boiler making it impossible to access the screws to remove the motor section. The whole pump had to be unplumbed to replaced the drive coil unit. When the pump failed the heating engineer took it out of the boiler and refitted in the pipe work external to the boiler. The owner of the boiler was impressed that the engineer had arrived with a dummy pump to fit in the boiler.

    It may be crap in your opinion, or it may be that some boiler designs are crap due to cost cutting.
     
  12. Dan Robinson

    Dan Robinson

    Joined:
    1 Jul 2007
    Messages:
    56,034
    Thanks Received:
    9,420
    Location:
    Hertfordshire & London
    Country:
    United Kingdom
    Bullsh|t. The boilers are the same size. Some might be taller than others, but the depth of a boiler will be the same throughout the range. The Intergas is super slim and full dismantable back top bare chassis in under an hour; and the same again to reassemble. Combi's are no harder to fault find than any standard heat only/system boiler configuration. It is just that all the components are in the box on the wall rather than spread about. I can't think of a single boiler on the market that has a different depth or width between the combi, system and heat only variant.

    What "slimline combi? One that you might be thinking of? So one boiler you have a recollection of equates to the whole boiler market? Vaillants for example are a doddle to service.

    This same mystical boiler? Wooshitter Blocth are a pig for some components; but that's why they bride Which? and label themselves "the installer's choice" - as no service engineer in his right mind likes them.. Most others are fine. Again, combi's are no harder to fault find than any standard heat only/system boiler configuration with a hot water cylinder. It is just that all the components are in the box on the wall rather than spread about. Some are even easier due to the lack of concern over the three pipe rule.

    The only limitations of combinations boilers are the lack of immersion back up and the inability to service more than one appliance.

    So as usual you are talking a load of boolax based on some poor Googleering when you researched and bought your wreck of a boiler.
     
  13. simond

    simond

    Joined:
    26 Oct 2004
    Messages:
    5,232
    Thanks Received:
    465
    Location:
    Surrey
    Country:
    United Kingdom
    It's an oiler, Dan, so the combi versions are significantly larger because they need a heatstore inside.

    In fact, the flow rates are quite impressive through a heatstore boiler so perhaps the OP could reconsider the combi route with a larger power output.

    Also has he considered an external green box model? Around half the oil boilers we fit nowadays are outside. And oil is 10% cheaper than gas these days!


    Edit: worth pointing out that Bernard is pontificating about gas boilers too. When you do this for a job it is annoying to read his authoritatively pitched ramblings when his experience is limited to looking at what he has on the wall at home. That makes me a TV repair expert too.
     
  14. Dan Robinson

    Dan Robinson

    Joined:
    1 Jul 2007
    Messages:
    56,034
    Thanks Received:
    9,420
    Location:
    Hertfordshire & London
    Country:
    United Kingdom
    Ah - missed the oil bit - saw the reference to the Bunny :D.

    So we're talking even more space then? As every oiler I've run into has been huge. Even the small ones :LOL:
     
  15. bernardgreen

    bernardgreen

    Joined:
    3 Nov 2006
    Messages:
    25,827
    Thanks Received:
    2,572
    Location:
    Bedfordshire
    Country:
    United Kingdom
    It is not that limited. It includes a few years repairing PCBs for commercial heating systems. And recommendations to at least two boiler manufactures ( the well known ones ) about how to improve their product both of which suggestions were acted on.
     
    • Like Like x 1
  16. simond

    simond

    Joined:
    26 Oct 2004
    Messages:
    5,232
    Thanks Received:
    465
    Location:
    Surrey
    Country:
    United Kingdom
    The link between repairing PCBs, and advising members of the public on whether a combination boiler is best citing the layout of their internals is tenuous, isn't it?

    The internet forum is for everyone to have a point of view, and I'm sure your opinions are going to be far more valid than mine, and most here, on the design of boiler electronics. It's probably best to preface any assertions outside one's direct experience by saying so.
     
    • Like Like x 1
  17. Dan Robinson

    Dan Robinson

    Joined:
    1 Jul 2007
    Messages:
    56,034
    Thanks Received:
    9,420
    Location:
    Hertfordshire & London
    Country:
    United Kingdom
    On that basis I should be advising the Israeli government on Supercomputer imports and the customs protocols around the shipping of Patriot missile systems.


    But I won't ;).
     
Loading...

Share This Page