Vented System Balancing - DHW Tank

Discussion in 'Plumbers' Talk' started by Jimbo, Dec 8, 2018.

  1. Jimbo

    Jimbo Active Member

    My system has three zone valves, one of which controls the hot water tank.

    I've noticed that when the water is being heated, the return temp is really high and the rads don't really heat up.

    Should there be a flow restrictor on the tank?
  2. kiaora

    kiaora Well-Known Member

    Yes, quite often there is a gate valve in the pipe work to tweak the flow rate down,
    Has it been fully opened by mistake?
    Or not one fitted?

    Mike83 likes this.
  3. Jimbo

    Jimbo Active Member

    So it does indeed, wide open :) Thanks.

    That gate valve is then T'd into another one that forms a bypass circuit. Why would that ever need to be open?
  4. Heat

    Heat Well-Known Member

    Sounds like you have 2 faults, -
    The first fault is the balancing gatevalve is full open, (this will need turned down greatly.) It will totally ruin the balancing of your system and reduce the heat of the rads.

    Second fault is a permanent bypass is also there. (Systems all need somewhere for to keep a circuit flowing so to keep pump circulating if TRVs or zone valves turn off. Also takes heat from gas boilers and can prevent pump over on some open systems.)
    You need a proper bypass valve fitted so that it only opens when system requires it. Only costs about £20 or less. Needs set by a heating engineer.
    Mike83 likes this.
  5. Mike83

    Mike83 Well-Known Member

    Just something to add.
    The make and model of boiler will help determine whether the system requires a bypass.
    I see them fitted in situations when it’s not required.
    But also come across systems were one isn’t fitted but clearly required.
  6. Jimbo

    Jimbo Active Member

    Thank you for the replies.

    Boiler is Worcester Greenstar Camray 18/25 (oil) in an open vented configuration. According to the manual:

    “An automatic bypass valve must be connected between the heating flow and return where TRVs are used on all radiators, fitted to give at least a 3 metre circuit when activated.”

    We have two rads without TRVs in the system so I think this can stay shut. Next time it’s drained I might add a bypass valve anyway since the piping is all there - I see our hosts carry them as well :)

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