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Home Made R.C.D. tester.

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Fred down the pub said that I can save money by not using a qualified sparks to test my R.C.Ds. He said that I can make my own R.C.D. tester. Is it safe? 

How to make RCCB tester at Home - YouTube


Z.
  • 0
    In a word - no!


    You can't use any old light bulb as an earth leakage test. You need to consider the minimum trip current specified. The test device must draw this minimum current, so the resistive element must be suitably chosen.
  • 0
    Agreed.

    To "TEST" a 30mA RCD then a suitable resistor must be chosen to draw 30mA at voltage supply.

    Example 8K2 resistor would give 29.27mA at 240v. (7W resistor rating).

    Of course you would not know the time taken for the trip to occour but it would work in RCD TEST BUTTON fashion.

    Adequate fusing required and how do you mitigate a non trip prior to disconnection?

    It`s a good example of "Don`t try this at home"
  • 0
    It is about the same level of precision as pressing the test button on the RCD, an uncertain  current of unknown duration. Some reassurance in weeding out totally stuck  RCDs and mis-wired sockets perhaps, but I agree a test of limited value. I have made a ramp test/headroom checking rig with several resistors and switches in the same sort of way.


    A real tester allows a known current, and also cuts off the test after a short time if it does not trip, so less risk to users if used  on a faulty installation.

    M.
  • 0
    Of course it cannot be used for RCD testing for compliance with BS 7671 as it does not comply with BS EN 61557-6.
  • 0
    For "proper "testing of an RCD a proper calibrated tester is needed.


    For simple go/no go testing, a crude test by briefly connecting a lamp  between phase and earth is better than nothing and undeniably  works to an extent.

    A low power lamp is advised, and proper precautions should be taken. A traditional "Drummond test lamp" is useful for this. Such test lamps are intended for safe testing of live circuits, unlike a random bulb and bulb holder.

    A poor substitute for a proper tester, but useful for a simple "does it trip or does it not" perhaps before use of an unknown supply.


  • 0
    Denis McMahon:

    In a word - no!


    You can't use any old light bulb as an earth leakage test. You need to consider the minimum trip current specified. The test device must draw this minimum current, so the resistive element must be suitably chosen.


    Yes but it does work, and the R.C.D. trips off  very quickly. Reg. 643.8 says that a current equal to, or higher than, five times the R.C.D's rated residual operating current is required for the test. So a 15 Watt lamp will provide this.


    Z.


  • 0
    John Peckham:

    Of course it cannot be used for RCD testing for compliance with BS 7671 as it does not comply with BS EN 61557-6.


    Haven't we left the EN bit of that now John?  Also, 643.1 allows other measuring equipment to be used.


    Z.


  • 0
    OK, time for a bit of refinement. Get a computer with a microphone and record from clicking the switch to the RCD tripping. That will give you a good indication of the tripping speed. ?
  • 0
    ebee:


    Adequate fusing required and how do you mitigate a non trip prior to disconnection?

     


    The M.C.B. will open in most cases if there is a large fault. The video shows a round pin plug, so the final circuit will be protected by a 15 or 16 Amp M.C.B. In the U.K. we could always use a 13 Amp plug fitted with a 3 amp fuse and suitable flex rather than singles. Or  an approved test lamp as has already been suggested.


    Interestingly I have a modern L.E.D. test lamp/Voltage indicator that trips R.C.D.s when I put one probe to L and the other in E, or one in N and the other in E if other loads are connected.


    If the R.C.D. trips instantaneously under test it is o.k. If it fails to trip it is broken and should be replaced. If it hums and buzzes and struggles to trip instantaneously, or trips off perhaps after a few seconds,  it also should be binned.


    After all a test button as used by a householder, if ever they do use it, does not indicate the trip off time. It is just a go/no go test.


    Z.




     


  • 0
    Haven't we left the EN bit of that now John?

    Nope, the UK (well just GB really) has only left the EU, we're still members of CENELEC.

       - Andy.

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