Setting of an automatic bypass valve

Discussion in 'Plumbers' Talk' started by Steved101, Sep 14, 2008.

  1. Steved101

    Steved101 New Member

    Sorry if this sounds silly but how do you know what setting to set an automatic bypass valve at?
    The valve is fitted just after the pump and just after the last return tee (from the hot water cylinder). it has a red plastic cap/handle - but what setting is best to set it at? I presume it has already been pre-set by the installers but i'd like to know for future reference and so I know it will properley open when the pressure builds up from TRVs closing.

    I thought it a bit strange a bypass circuit/valve was even fitted, as the radiator in the hallway where the room stat is has no TRV and could act as a bypass, the boiler is a Gloworm (and obviously doesn't have a bypass built inside) which a lot of boilers do now I believe? It's just a conventional condensing boiler.
  2. rome60

    rome60 New Member

    On modern boilers with pump overun it must have a automatic byepass valve,which opens when motorised valves & TRVs close.This is what an interlock is as stated in the regs.The auto byepass then closes when the temperature drops on the high limit stat in the boiler & shuts down the pump.To set the auto bye pass set it to the high number turn off rad valves,run boiler & turn down Auto byepass until water is curculating through the byepass.;)
  3. Steved101

    Steved101 New Member

    how do you know if water is running through the bypass!??

    you don't always need pump overrun to have a bypass installed though as my boiler manufacturrers instructions don't state a pump overrun! the pump and bypass valve/circuit are both in the airing cupboard also.
  4. mully123

    mully123 New Member

    Contact manufacturer of valve,they will have the instructions of how to set according to how your system is designed.It should have been set on commissioning of your system
  5. G Brown

    G Brown New Member

    stop fiddling Steve and finish your college course ;)
  6. rome60

    rome60 New Member

    Read my post & start the system from cold & feel the pipe temperature turn the auto valve to lower number slowly until the pipe starts to get warm then it is bye passing.;)
  7. rome60

    rome60 New Member

    Mully, your suggestion can not be done via phone,to much technical info would be required,easy to do it the practical way on site as i suggest.;)
  8. mully123

    mully123 New Member

    Romeo,didnt say by phone,get the instructions is i think what i said,i know fully well that the valve is about resistance and pressures,but sometimes theres more loss going round the bypass,which is a waste of energy,why would he want to even bother touching it,if you look at his other posts he dosent understand how it all works,hes been sussed.
  9. heatyman

    heatyman Member

    commissioning of your system

    very few are set as they should be. The pressure needs to be set just below the highest pressure shown on the performance curve for the circulator; it will then do what it is supposed to do which is protect the pump.
    Martin
  10. Razor69

    Razor69 New Member

    The bypass is there to protect the pump but also to prevent the water in the boiler being overheated by the residual heat causing kettling and banging.
    The boiler interlock is not the bypass its just a way of stopping the boiler firing when there is no heating demand, usually the roomstat provides this which is why there is no trv on that rad.
    You will have a bypass valve fitted if you have 2 2 port valves but it is not usually needed if you have one three port valve.
  11. Dick Puller

    Dick Puller New Member

    Again 'heatyman' has got it. As for the rest of you chancers, you're clueless.

    Put the system on CH only & turn all TRV's off. Thus putting the system into the condition when the BP valve should kick in. Adjust the valve until you feel the valve by-passing, the return getting hot.
  12. rome60

    rome60 New Member

    Dick,i am not a chancer if you read my posts at the start of this subject,what you are saying is exactly what i have said.:)

    What heatyman is saying is correct,but to work out the pump delivery the whole system pipework curcuits& sizes are required to preset the auto byepass valve,best to do it your & my way practical adjustment.;)
  13. Dick Puller

    Dick Puller New Member

    Listen lads;
    Don't make a sound when the Master is around!!

    All you CC & CCC's must be green with envey when you read my posts.........''That ole git knows his onions all right''.

    One day, you can sit with me, kiss my ring & listens to my teachings. My words are pure & my knowledge is extensive, so don't talk as you are foolish & know nothing of the wonders of my craft........Hang on my every word & learn!!!
  14. heatyman

    heatyman Member

    valve,

    Not so, you only need to look at the pump performance curve,-- as long as the valve is in the right place!
    Martin
  15. heatyman

    heatyman Member

    I see the last line quote original has struck again, this in in reply to Rome's post about working out hydraulic performance.
    Martin

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