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central heating pump on return

  • 11-06-2012 10:22PM
    #1
    gmk77
    Registered Users, Registered Users 2 Posts: 14 ✭


    I have a central heating pump that's fitted on the return. I had some work done on some leaky pump isolating valves and now I'm worried that the pump's been re-fitted the wrong way round. If the pump is on the return, should the arrow be pointing towards the boiler?


Comments

  • #2
    heinbloed
    Registered Users, Registered Users 2 Posts: 1,632 ✭✭✭heinbloed


    If the pump is on the return, should the arrow be pointing towards the boiler?

    Yes.


  • #3
    gmk77
    Registered Users, Registered Users 2 Posts: 14 ✭gmk77


    Thanks, I've noticed that the central heating works but the UFH does not work. I don't understand why the central heating is working if the pump is pumping the wrong way. Surely the boiler should just cut out if the water is flowing in the wrong direction?


  • #4
    Billy Bunting
    Registered Users, Registered Users 2 Posts: 2,842 ✭✭✭Billy Bunting


    heinbloed wrote: »
    Yes.

    we'll make a plumber of you yet. :D


  • #5
    DGOBS
    Hosted Moderators Posts: 3,496 ✭✭✭DGOBS


    The boiler will work with the pump the wrong way around, but not very well as stats etc are all on the flow side.

    If the pump valves have just been changed it will be a quick job to turn it around.

    5***** Heinbloed!


  • #6
    heinbloed
    Registered Users, Registered Users 2 Posts: 1,632 ✭✭✭heinbloed


    Surely the boiler should just cut out if the water is flowing in the wrong direction?

    No. The boiler cuts out once the limits are met.It works(fires) independently from the pump's behaviour. If the boiler gets to hot, bejond the (set) limit it cuts out. If it gets to cold it kicks in.

    The pump belongs on the return as principle, it would last longer there and creates a positive pressure in the boiler. This pressure guarantees a fast flow through the boiler, pushes out air.
    With high temperature closed/pressurised CH systems it is very important to have the pump on the return, a safety issue: the pump can also create a negative pressure, meaning the water in the boiler will start to boil below 100 degrees Celsius.
    And this in turn will generate steam which can destroy pump and boiler and more.

    So put the pump on the coldest pipe which is usually the return pipe. As a principle.

    About the non-working UFH: are the valves open?


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  • #7
    gmk77
    Registered Users, Registered Users 2 Posts: 14 ✭gmk77


    All the valves etc. Are open. The UFH actually works fine if it's used with something else - e.g. If the rads and UFH are both on then it's fine. However, when the UFH is on by itself the water in the boiler starts to boil and it goes haywire. This is all since the central heating pump valves were changed. This got me thinking about the direction of the pump and that maybe the central heating pump and UFH pump are working against each other.


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