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Discuss Peak hourly load rates in the Gas Safe Register Forum - Public Forum area at

  1. Psbjj1

    Psbjj1 New Member

    Hi all, I have a customer who has 2x 37kw boilers and a 7kw hob.

    These are supplied from a u6 meter and a 25 metre pipe run in 22mm.

    I've told him he needs to upgrade both meter and pipe run. His energy supplier have come back asking for peak hourly load.

    Is this a case of adding gas rates or do I need to take into account CV and diversity factors?

    All help appreciated. Can't find my viper book for the life of me so I've ordered a corgi one for the meantime.
  2. Craig Watson

    Craig Watson Plumber GSR Top Contributor!!

    Isn't any installation exceeding 70kw classed as commercial? Are you registered for commercial gas?
    • Agree Agree x 3
  3. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    25 m of pipe for that you have pretty much zero chance of it being in scope. You could obviously work on each boiler individually but without being able to work on the whole caboodle it’s a bit of a waste of time
  4. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    i would say around 9m3/h so u16 meter also commercial and under gassed atm hope youve turned them off
  5. king of pipes

    king of pipes Trusted Plumber GSR Top Contributor!!

    As above a u6 will only pass enough gas for 60kw so a u16 is needed the pipework will need upgrading something you cannot do on a domestic ticket. You should be turning one of those boilers off and go as far as capping the gas to it and attaching a warning notice and complete the relevant paperwork . Kop
    • Winner Winner x 2
  6. firemant

    firemant Plumber GSR

    Good point, Craig. But there is no way it is actually consuming 70Kw :)
    • Agree Agree x 1
  7. bill577

    bill577 Member

    Really depends on what the boilers are, if they are combis the diversity factor would bring them and the hob back into domestic territory.
  8. robdog6000

    robdog6000 New Member

    It sounds hugely under-gassed. I would be concerned about the hob going out with both boilers firing.

    The commercial/domestic registration thing needs some clarification. I have heard so many differing opinions of the regs. Can anyone enlighten me?
    • Agree Agree x 1
  9. Craig Watson

    Craig Watson Plumber GSR Top Contributor!!

    The points I remember are
    1.Any installation over 70kw is classed as commercial.
    2.Any installation where the installation pipe work is greater than 35mm
    3.If the total gas volume of the installation goes over a certain amount (can't remember the figure)
    4.Any gas meter bigger than a u16
    5.And I also think if commercial appliances are used,
    • Agree Agree x 2
  10. robdog6000

    robdog6000 New Member

    Thanks Craig. Its the 70kw cut-off limit which I wasn't sure of. Does that mean that you can't work on any pipework on a system over 70 kw?

    I thought a lot of the regs are based on purge volumes rather then the load of the system.
  11. Craig Watson

    Craig Watson Plumber GSR Top Contributor!!

    Yeah, so with regards to op's system, if I turned up, I would simply say because your installation is over 70kw, I can't work on it.
  12. Mastermixlee

    Mastermixlee GSR

    Hi everyone, my first posting here.

    It is my understanding that you can't work on Boilers on a system that are on the SAME system (2 Boilers connected to same central heating circuit) if combined kW rating exceeds the 70.
    But if, for example, the left boiler was zoned off on its own pipework feeding upstairs and the other boiler was feeding downstairs then its deemed acceptable to work on under domestic ticket provided the gas supply checks are OK as mentioned by Craig above.
  13. Craig Watson

    Craig Watson Plumber GSR Top Contributor!!

    I believe the gas supply would have to also be on a separate circuit too, gas isolation valve with test nipple after it so you can test the gas independently of the rest the system.
    • Like Like x 1
  14. robdog6000

    robdog6000 New Member

    Cheers for providing some clarity on this. I often work on large domestic houses with u16 meters. The heating and gas design is designed by a consultant and he has us fitting isolation and purge valves all over the place.Costs the poor customer a fortune but I guess it covers us working on large systems.
  15. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Yea really you shouldn’t be doing the gas if it’s over spec should get a commercial engy to install the pipework and valves

    Then a domestic engy can fix / install from the valves
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