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IR test bellow 1Meg

MrJack96
Is it dangerous a low reading such as 1Kohm for IR I know you need to seriously investigate but if a 3 phase submersible pump is installed correctly wouldn’t the breakers/ fuses blow before the equipment is unsafe. 


230/1000 =0.23ma? 


  • 0
    MrJack96:

    The measurements were at the motor.


    So were you measuring the IR of the motor, the IR of the fixed wiring, or both in parallel?


  • 0
    Both in parallel. So when we mean two separate faults we mean bad IR as well as a loose or disconnecting earth. If it’s connected to earth properly would it be a real cause for concern as body’s resistance is 1000ohms approx? Thanks for your detailed replies guys. Suppose best idea is to barrier off and label till a replacement is in place.
  • 0
    Normally the earth connection (CPC ) is a thing that is nice to have, but mostly things  will work without it - I imagine already that  can hear the boos and  hisses from the audience already - it has been quite a long time since 2 pin plugs were accepted  in the UK - I can't recall seeing one in use after about 1980, and I have only ever removed them never installed a new one..


    So maintenance chaps and so on are quite easy going about removing chunks of pipe and wiring and odd clamps to them and leaving it unearthed while they work and (we hope) putting it all back later.


    So long as the motor is now, and remains, well earthed, it is perfectly safe to touch, but faulty.

    However, if somehow the earth path is not low resistance, then, and only then  it actually becomes dangerous.

    Even then it is only dangerous if someone is well connected both to it, and to a better earthed thing,  at the same time.

    Then  what happens next is all down to how the fault resistance and their body resistance divide the volts up on the day - nervous sweating and full hand contact is much worse then a brush with the back of the knuckles - not least because the current makes the muscles twitch, and in most healthy folk the clenching  muscles are stronger than the relaxing ones, giving a no-let go to any shock on the front of the hand, but a rather violent  pull away and self disconnection on the back and  also because sweat is partly conducting and makes the effective contact area bigger and knuckes are usually drier than palms.

    .

    Sorry if this is labouring the point.

    yes, if there is a risk folk may go near it for maintenance, cleaning or whatever, to put some sort of notice/barrier showing that a fault is suspected and to keep out until fixed , is very sensible

    M.
  • 0
    MrJack96:

    Both in parallel.


    And is that L-L or L-E; and if the latter, just one L, two, or all three? I would suggest that you disconnect the motor and find out whether the fault lies in the motor or the fixed wiring (or both). It may seem like teaching Granny to suck eggs, but don't you need to establish where the fault lies before you can fix it? ?


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    That really does need to be investigated. The RCD is an extra level of protection but should never be relied upon if possible. RCD's can fail, especially if they are overloaded over an extended period, or very overloaded over a short one. Hence the requirement for regular testing and using the button.

    Find and treat the cause of the problem, don't rely on an RCD to deal with the symptoms.

    Final thought, if it is a 3 phase with neutral and the motor is connected in star mode, then the low reading could be due to current coming back through the windings to neutral, which is also connected to earth. Disconnect the neutral for your measurement.

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