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short circuit in my friends flat

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  • 16-02-2011 12:19pm
    #1
    MungoMan
    Closed Accounts Posts: 353 ✭✭


    My friend has a short circuit in his flat in Dorset street

    When he turns on the water, it activates a pump (to pressurise the water)

    This does NOT cause the circuit controlling the pump to short.

    Instead, it causes the circuit controlling the electrical sockets to short....

    Sounds like water may be the reason, there is no evidence of a leak however....

    Once the tap is turned off, then resetting the trip switch makes the electrical circuit available again (and the television can be turned on again !)

    Any advice about getting someone around to diagnose and fix the problem (can PM me). Or post a name on the main forum if thats not in breach of rules)

    Anyone hazard a guess as to what might be causing the problem ?


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    #2
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    MungoMan wrote: »
    My friend has a short circuit in his flat in Dorset street

    When he turns on the water, it activates a pump (to pressurise the water)

    This does NOT cause the circuit controlling the pump to short.

    Instead, it causes the circuit controlling the electrical sockets to short....

    Sounds like water may be the reason, there is no evidence of a leak however....

    Once the tap is turned off, then resetting the trip switch makes the electrical circuit available again (and the television can be turned on again !)

    Any advice about getting someone around to diagnose and fix the problem (can PM me). Or post a name on the main forum if thats not in breach of rules)

    Anyone hazard a guess as to what might be causing the problem ?

    It sounds like an earth fault or problem in the pump, it does not have to be a short circuit to trip the sockets RCD which it sounds like is whats tripping. The RCD is very sensitive to earth faults which are not uncommon in water type devices. Does the pump also go off when the sockets go off? Either way, the problem is likely with the pump itself, and thats what will need to be looked at first. Check it for any signs of dampness etc. An electrician can confirm if the pump is the problem. The connections into the pump need to be looked at as well for signs of dampness or a problem in the terminal box if it has one.

    I assume the pump was working before this and was not just newly installed or modified, and caused this problem immediately, as a circuit wrongly connected at the main board can cause this also.


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    #3
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    pump- more than likely alright


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    #4
    beanie10
    Closed Accounts Posts: 466 ✭✭beanie10


    As Robbie said.
    Neutral earth fault in pump windings,as the windings only come into circuit when water pressure drops.Pump needs to be changed.
    Did it ever work peoperly?


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    #5
    MungoMan
    Closed Accounts Posts: 353 ✭✭MungoMan


    Thanks

    On further examination, it's the earth leakage trip switch which is tripping (as Robbie and others have correctly suspected)

    What confuses us is that the pump keeps working when the earth leakage trip switch trips..........

    Any explanations for this ?


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    #6
    MungoMan
    Closed Accounts Posts: 353 ✭✭MungoMan


    beanie10 wrote: »
    As Robbie said.
    Neutral earth fault in pump windings,as the windings only come into circuit when water pressure drops.Pump needs to be changed.
    Did it ever work peoperly?

    Yes the pump has worked properly for 8 years since it was installed.


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    #7
    beanie10
    Closed Accounts Posts: 466 ✭✭beanie10


    It sounds like a damaged earth or neutral problem, ive come across this before and the only way i could solve it was by disconecting one earth from the board at a time until the problem stops and that should be your troublesome earth.
    Was there anybody working on the board recently
    You will need a qualified electrician to solve this.


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    #8
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    MungoMan wrote: »
    Thanks

    On further examination, it's the earth leakage trip switch which is tripping (as Robbie and others have correctly suspected)

    What confuses us is that the pump keeps working when the earth leakage trip switch trips..........

    Any explanations for this ?

    It sounds like you possibly have a neutral earth fault on a circuit controlled by the RCD, possibly a circuit that is not in use, because if it was in use then this circuit would trip the RCD itself. It could be a socket circuit with nothing plugged into it, or immersion circuit not used. Add in an earth fault on the motor and this can divert through the earth bar onto the fault on the other circuit and to the RCD neutral bar but usually only if the house is not neutralised, or if the earth bar is not properly earthed in the MCB board.

    A small current can also divert from the main neutral which the pump is connected to through the RCD to the RCD neutral bar and onto the earth fault on the other circuit, but in this case, usually other large loads such as a cooker would trip the sockets RCD. A way to test this would be to put every item on the electric cooker on at the same time for a minute, if you have an electric cooker, or electric shower might do it too.

    Sometimes there is earth leakage combined from circuits which is just below the threshold of the RCD and now its just passed it. Try switch off every MCB the RCD controls and see of the pump now trips the RCD, even though its not fed through it.

    The pump should be through an RCD, is it through one at all?


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    #9
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    beanie10 wrote: »
    It sounds like a damaged earth or neutral problem, ive come across this before and the only way i could solve it was by disconecting one earth from the board at a time until the problem stops and that should be your troublesome earth.
    Was there anybody working on the board recently
    You will need a qualified electrician to solve this.

    Yes not a bad idea with the earths, have done that before too. Can be tricky to find what earths are doing what as well though. Someone else at the board also worth a suggestion. Qualified man needed for sure.

    Last time i seen a similar problem was a nail through a socket twin and earth which shorted the neutral to earth, switching on the cooker tripped RCD. No one was living in the house most of the time so nothing plugged into sockets.

    The affected twin and earth was nailed when ceiling coving being put up. the same piece of twin and earth was nailed twice in 2 different rooms, both times shorting earth to neutral. Considering both drops had 2 twin and earths, it was bizare and unlikely for that to happen twice to the same actual piece of cable.


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