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Twin Impeller Shower Pump

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Ref. Grundfoss STP-2.0B twin impeller shower pump. 2.2 Amp. 510 Watts. 240 Volts.


Will this pump be o.k. run through a B6 M.C.B. or will it trip the B6 on starting do you think?


Thanks,


Z.
  • 0
    Several times I have made the electrical connections to shower pumps and left them for the plumber to connect the pipework ready to commission, then got a phone call to say there’s something wrong with the electric supply as the pump won’t work.


    So you go back knowing there’s nothing wrong with the electrical connection to find plastic pipe and fittings looping all over the airing cupboard and bathroom full of airlocks along with a low head and thermostatic mixer shower all preventing sufficient water to flow to trigger the positive head shower pump.


    I’m not saying it’s impossible to use a positive head shower pump, but I’m very wary of them now.


    You need to use a flex connection plate, 20-amp double pole switch, a switched fused connection unit, a plug and socket or something similar to make the transition from the circuit cable to the pump flex, really the choice is based on location on the pump, most of the time a SFCU is ideal leaving the choice of circuit protective device wide open.


    Andy
  • 0

    Sparkingchip:

    Several times I have made the electrical connections to shower pumps and left them for the plumber to connect the pipework ready to commission, then got a phone call to say there’s something wrong with the electric supply as the pump won’t work.


    So you go back knowing there’s nothing wrong with the electrical connection to find plastic pipe and fittings looping all over the airing cupboard and bathroom full of airlocks along with a low head and thermostatic mixer shower all preventing sufficient water to flow to trigger the positive head shower pump.


    I’m not saying it’s impossible to use a positive head shower pump, but I’m very wary of them now.


    You need to use a flex connection plate, 20-amp double pole switch, a switched fused connection unit, a plug and socket or something similar to make the transition from the circuit cable to the pump flex, really the choice is based on location on the pump, most of the time a SFCU is ideal leaving the choice of circuit protective device wide open.


    Andy 




    That is why I have installed a dedicated labelled 13 Amp socket outlet for the new pump, and I have fitted a 13 Amp plug onto the pump flex fitted with a 5 Amp fuse. So, as I explained to the customer, it will aid installation and make a renewal easier in a few years time when the pump needs renewal. Also, electrical isolation is obvious, so that will keep the plumber happy.


    Z.

  • 0
    That post reminds me that It has often amused me that in many textbooks an introduction to electrical theory  is 'simplified' by considering it to be like some closed circuit plumbing with pumps and things.

    This simplification is at odds with real plumbing that has some really nasty gotchas, like air locks, gravity circulation by convection, non-linear resistances in the form of pressure drop nothing like proportional to flow,  transmission line resonance effects  like water hammer etc .

    In many ways I have often wondered if it might be easier the other way about and to 'simplify' the explanation of the principles of plumbing by pretending it is like electrics... so we can say things like "these radiators are like resistors in parallel across the boiler"
  • 0

    mapj1:

    That post reminds me that It has often amused me that in many textbooks an introduction to electrical theory  is 'simplified' by considering it to be like some closed circuit plumbing with pumps and things.

    This simplification is at odds with real plumbing that has some really nasty gotchas, like air locks, gravity circulation by convection, non-linear resistances in the form of pressure drop nothing like proportional to flow,  transmission line resonance effects  like water hammer etc .

    In many ways I have often wondered if it might be easier the other way about and to 'simplify' the explanation of the principles of plumbing by pretending it is like electrics... so we can say things like "these radiators are like resistors in parallel across the boiler"




     

    You may have as many radiators in parallel as you like, but let's keep it simple and have one.


    One volt, one ohm, one amp. Now let's increase the resistance. One volt, one kilohm, one milliamp.


    But ...


    One meter head of pressure, one radiator two metres above, and no flow at all.


    So which animal has the highest blood pressure?
  • 0
    Before going back to look at one shower pump I spoke to the customer who was speaking to me on a cordless phone, so I said to him go into the bathroom and turn the shower on, he did that and said the shower isn’t working, so I said lift the handset out of its bracket and lower it down into the bath, he tried this when he had the handset at knee height the pump kicked in, the customer then said he could see it was not an electrical problem.


    Anyway going back to the original post, why a 6-amp breaker rather than a 10 or 16?
  • 0
    “But ...


    One meter head of pressure, one radiator two metres above, and no flow at all.”


    Unless?
  • 0


    "In many ways I have often wondered if it might be easier the other way about and to 'simplify' the explanation of the principles of plumbing by pretending it is like electrics... so we can say things like "these radiators are like resistors in parallel across the boiler" "


    regards Mike



     


    Oh Mike, steady on lad, you`d get folk imagining that electrics is easy and plumbing difficult when we all know it`s t`other way around ?

  • 0
    That is sort of my point, for me, and I suspect some others  on this forum  it is indeed  the wiring that is more intuitive and usually  less aggro than the plumbing.

    I cant recall ever having an electron leak that damaged a previously good carpet, and stained the ceiling below, but the hot water cylinder in the cupboard off the landing and the plumbing to it from the boiler, well that's quite another story.


  • 0
    Those electrons can be pesky little blighters when they start nibbling you and also they sometimes start attacking some building fabrics too ?
  • 0
    A central heating system is a closed loop, for the first half of the circuit the pump is applying a positive pressure and pushing the water, in the second half of the circuit the pump is applying a negative pressure and pulling the water.

    However at the midpoint of the circuit the pump is neither pushing or pulling the water are no pressure either positive or negative is being applied. So the water can stall particularly if there is a restriction or air lock as the water cannot overcomes it.

    Swapping the pump for a bigger one in the same location may not alter anything as the neutral point is is there in the same place and nothing has really altered, moving the position of the original pump or altering the pump may actually have the required effect that installing a larger pump failed to do.


    The positive head shower pump needs gravity flow of water to trigger it, is there is an air lock in the pipework or cylinder and the flow is restricted by the pipework or the thermostatic mixer valves in the shower it won’t turn itself on.


    Installing pumps or replacing existing pumps with bigger pumps cannot always overcome issues created by badly installed plumbing.


     Andy

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