Combi or Unvented for a 6 bed house?

Discussion in 'Plumbers' Talk' started by AlexJ, Oct 26, 2015.

  1. I think I'm sold, Walt.

    yep, it did occur to me that the boiler's system is chust a wee loop betwixt it and the cylinder, so no sludge build up, and no blocked exchangers.

    (I'd still go for an unvented boiler tho' - who wants a bludy tank in t'loft? And ditto for the cylinder - that has a wee expansion tank fitted, doesn't it?)
     
  2. Walt Systems

    Walt Systems Member

    The vented thermal store has one small header tank just above it, or in the loft If you want. That does the thermal store and boiler. Think of the thermal store when directly heated by the boiler as a large water section extension of the boilers heat exchanger, making it a large water capacity heat exchanger, like some oil boiler are.
     
  3. plumber-boy

    plumber-boy Well-Known Member

    Walt you really are an idiot that's spends all his day goggling, this is my last post on this subject as I know for a fact that you are no plumber or heating engineer.;)
    Good bye keyboard warrior I'm sure RY will be along later to hold your hand.:p
     
    Dave does Gas likes this.
  4. Walt Systems

    Walt Systems Member

    Right on time... I wrote:
    "Beware of so called "professionals" who say a Vaillant and unvented cylinder is the only way to go. No doubt these "professionals", who specialise in drains, will come back with ad hominem attacks, with technical substance and experience lacking. Wait and see. It is hilarious to read. Guaranteed to happen. :)"​

    You didn't have a clue what I was on about. It is outside your jobbing plumber experience. Not the sort of thing the guy at the trade counter can tell you about and sell to you. Sad really.
     
  5. I don't think Walt is a Googler, P'Boy; I suspect he's a legit plumber. And he's been on this forum for a loooong time. Saying the same thing.

    I'm not a plumber, but I can follow the principles. And when I looked at a couple of videos on the Gledhill, I was impressed by what I saw.

    It does make sense, but what I don't know is if - in a normal household with chust a gas boiler - it is more economical than, say, a Megaflo. The boiler has to run at 75oC for example.

    But it does look good, and if there is another source of energy - solid fuel, PV etc - then it seems to be an excellent way to harness it all.
     
  6. Walt Systems

    Walt Systems Member

    The boiler can run at just over 60C, depending on the size of the plate heat exchanger. The bigger the lower the store temp as more heat is extracted from the stores water. Also the return temperature can be as low as few degrees above the cold water main temperature. Also having larger rads to run at lower temperatures aid condensing. Condensing boilers condense almost 100% of the time. Cycling is very inefficient as on a directly heated rad system. Boilers do not cycle directly reheating thermal stores. They run until up to temperature, then switch off until the store depletes significantly, then come on to reheat for long burn. One long efficient burn is very efficient.

    Most condensing boilers controls will maintain a temp differential between the flow and return. If it is 15C from the store into the boiler, it my not have the flow temp above 45C. As the store warms the flow temp gradually rises. Onlt at the very end of as reheat will condensing stop occurring.

    A megaflow is just a hot water cylinder. A thermals store is very different, even though DHW thermal stores are available.
     
    Last edited: Nov 2, 2015
  7. Walt Systems

    Walt Systems Member

    I am not a plumber. I am a graduate engineer. I don't swing on stilsons. We tell them what to do. They follow what we design.
     
  8. Ryluer

    Ryluer Well-Known Member

    Lots of people do. But the modern plumber always wants the easy way out.
    I worked in a lot of office blocks and the engineers always specified a big cistern on the top floor.
    Stored water delivered directly always gives the best performance. When you start passing through heat exchangers that's when performance drops.


    But when the mains isn't up to the job that's where gravity comes in. Not big accumulators that need servicing and replacing forever.
    The OP need to have his mains tested. He needs 20/l min @1 bar dynamic minimum for an unvented cylinder. (megaflow specs)
     
  9. Ooh, just a touch arrogant there... :rolleyes:
     
    steverod likes this.
  10. steverod

    steverod New Member

    John Delorean was a graduate engineer. Kind of says it all...
     
  11. Walt Systems

    Walt Systems Member

    He made a great car. That even went into the future.
     
  12. steverod

    steverod New Member

    Sorry to break it to you but that wasn't actually real, it was only a film. The real car couldn't do that. It was just an over complicated engineering solution to a problem that didn't exist, and managed to lose millions of pounds for the British taxpayers.
     
  13. Ooh, just a touch serious there... :rolleyes:
     
  14. Walter System

    Walter System Member

    It was real and it was great car.
     
  15. miss pickle

    miss pickle Well-Known Member

    Morning Walt smileys-waving-170093.gif

    I don't think it was really real :oops: but if you think about it everything is always going in to the future isn't it smiley-confused013.gif or is that not right?
     
  16. Walter System

    Walter System Member

    Miss Pickle, you must look ahead. How things happened in the 1970s doesn't apply today. But that car was real. Very real. It said so on the film.
     

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