Pre plumbed Unvented cylinders with pumps on

Discussion in 'Plumbing and Central Heating' started by Lrsd, 1 Feb 2019.

  1. Lrsd

    Lrsd

    Joined:
    1 Feb 2019
    Messages:
    5
    Thanks Received:
    0
    Country:
    United Kingdom
    Hi

    Can anyone tell me why unvented cylinders come with pumps on? When system boilers come with the pump integral?

    Thanks
     
  2. Sponsored Links
  3. Dan Robinson

    Dan Robinson

    Joined:
    1 Jul 2007
    Messages:
    56,034
    Thanks Received:
    9,420
    Location:
    Hertfordshire & London
    Country:
    United Kingdom
    How does the cylinder manufacturer know what it's being plumbed into?
     
    • Thanks Thanks x 1
  4. Lrsd

    Lrsd

    Joined:
    1 Feb 2019
    Messages:
    5
    Thanks Received:
    0
    Country:
    United Kingdom
    Thanks for reply but was looking for more of a technical answer,

    So do all system boilers come with pumps integral?

    Unvented cylinders are mains fed so must be installed with system boiler.

    Ive seen some unvented cylinders installed with pumps fitted, i was just wondering what happens to the pump on the boiler that comes integral to the boiler?

    Or can you buy system boilers without the pump fitted?

    Thanks
     
  5. wwwebber

    wwwebber

    Joined:
    5 May 2004
    Messages:
    435
    Thanks Received:
    24
    Country:
    United Kingdom
    My unvented cylinder didn't come with a pump and my system boiler doesn't have a pump either but I do have an external pump that pumps the central heating and the indirect hot water. I dont really understand what you are getting at here.
     
    • Thanks Thanks x 1
  6. Lrsd

    Lrsd

    Joined:
    1 Feb 2019
    Messages:
    5
    Thanks Received:
    0
    Country:
    United Kingdom
    Thanks

    So the answer is you can buy system boilers without the pumps integral

    Thanks
     
  7. fixitflav

    fixitflav

    Joined:
    20 Mar 2018
    Messages:
    1,328
    Thanks Received:
    152
    Location:
    Stoke-on-Trent
    Country:
    United Kingdom
    No, then it wouldn't be a system boiler. A system boiler has in-built pump and expansion vessl. A heat-only boiler doesn't, it needs an external pump and either a F/E tank or a pressurised expansion vessel, depending on preference. Any of them can feed the primary coil of a HW cylinder, vented or unvented.
    One of my sons has a heat-only boiler (Glowworm) with external expansion vessel, feeding a pressurised HW cylinder.
     
    • Thanks Thanks x 1
    • Like Like x 1
  8. wwwebber

    wwwebber

    Joined:
    5 May 2004
    Messages:
    435
    Thanks Received:
    24
    Country:
    United Kingdom
    Good info. So mine is a heat only boiler feeding an unvented HW cylinder. The heating loop is also pressurised via an expansion vessel. Cheers.
     
    • Thanks Thanks x 1
  9. Lrsd

    Lrsd

    Joined:
    1 Feb 2019
    Messages:
    5
    Thanks Received:
    0
    Country:
    United Kingdom
    That makes sense, so when people convert from gravity fed to mains they can keep their conventional boiler as opposed to ripping out and fitting a new system boiler

    Just re using existing pump and installing pressure vessel

    Thanks
     
  10. Sponsored Links
  11. wwwebber

    wwwebber

    Joined:
    5 May 2004
    Messages:
    435
    Thanks Received:
    24
    Country:
    United Kingdom
    Correct which is exactly what I did. I had a pressure vessel put in to pressurise my heating system so that I could also remove the header tank in the loft etc (as well as the cold water tank). My unvented cylinder is pressurised of course but mine uses an internal expansion vessel to achieve this - some dont have this and need an external one to be fitted.
     
    • Thanks Thanks x 1
  12. Lrsd

    Lrsd

    Joined:
    1 Feb 2019
    Messages:
    5
    Thanks Received:
    0
    Country:
    United Kingdom
    Excellent, ive learnt something

    You must have a megaflo as they have the pattend internal expansion vessel
     
  13. ianmcd

    ianmcd

    Joined:
    15 Aug 2010
    Messages:
    23,973
    Thanks Received:
    10,075
    Location:
    Livingston
    Country:
    United Kingdom
    Not always, some boilers can be adapted some cant, if you convert from open vent to sealed, the boiler needs over heat and loss of pressure sensors of some kind, the external expansion vessel and pressure releif kit must also be installed, a system boiler has all these inbuilt, a heat only boiler doesnt
     
    • Thanks Thanks x 1
  14. wwwebber

    wwwebber

    Joined:
    5 May 2004
    Messages:
    435
    Thanks Received:
    24
    Country:
    United Kingdom
    Mine is not a Megaflow and it has an internal expansion vessel :) and yes, you need to check that your current boiler can be pressurised if indeed you want to pressurise your heating circuit. You can still have a unvented cylinder in either case but you must have adequate mains cold water pressure to run it.
     
    • Thanks Thanks x 1
  15. Gasguru

    Gasguru

    Joined:
    9 Sep 2005
    Messages:
    12,653
    Thanks Received:
    3,396
    Location:
    Sussex
    Country:
    United Kingdom
    And just to add that the larger system boilers come with expansion vessels and pumps that are far too undersized to be of any use.
    Far better to have a separate pump/vessel/safety valve/gauge/loop that can be properly sized....and you're not tied to extortionate manufacturers spares prices when they fail.
     
    • Thanks Thanks x 1
    • Like Like x 1
  16. muggles

    muggles

    Joined:
    28 Oct 2005
    Messages:
    13,427
    Thanks Received:
    3,104
    Location:
    Daventry
    Country:
    United Kingdom
    There are at least 3 brands I can think of who offer the floating baffle internal expansion system. I'm not sure any of them have made it work properly - generally more hassle than it's worth
     
    • Thanks Thanks x 1
  17. fixitflav

    fixitflav

    Joined:
    20 Mar 2018
    Messages:
    1,328
    Thanks Received:
    152
    Location:
    Stoke-on-Trent
    Country:
    United Kingdom
    I think it's been covered, but to recap - you can have a gravity-fed or unvented HW cylinder, with a system boiler, or heat-only boiler, in any combination. I believe system boilers always come with in-built expansion vessel, heat-only can be set up for gravity via F/E tank or pressurised with separate expansion vessel. There's pros and cons for each, starting from scratch it's probably a toss-up, but I wouldn't take out an existing F/E tank and go pressurised. If you do, you need to check the boiler is OK for the higher pressure, and there might be a bigger risk of pipework leaking. Also as ianmcd said, you need to add a pressure relief valve and a pressure switch to cut out on low pressure.
     
    • Thanks Thanks x 1
  18. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
Loading...

Share This Page