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AMD 2 - insulation testing

AJJewsbury
Looks like the DPC has made a bit of a change about insulation testing where some devices might be vulnerable to a 500V test voltage or distort the results. Previously we were allowed to either disconnect the item concerned (or do the test prior to initial connection) OR carry out a 250V test (with a 1MΩ limit to meet).


As I read it, a full 500V test will soon be required prior to connection of such equipment PLUS an additional 250V test (with a 1MΩ limit to meet) will be required after it is connected.


I can see the sense in that, in that it doesn't 'excuse' the rest of the circuit from a full 500V test, but I'm slightly uneasy about some equipment not being happy with a relatively long duration 250V d.c. test L&N - PE - especially if it has to meet a 1MΩ limit. Does anyone have any thoughts on that?


All strictly speaking for an initial verification - for a periodic we still seem to have the flexibility of choosing 'appropriate' tests (however that's going to be interpreted...).


Seems it's going to be a bit of extra work, especially if you've a house full of USB power sockets....


   - Andy.
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  • 0
    That is the advice that was / is given, but how well it is followed is another matter.  It's fine on small installations but on installations with many fittings that need to be connected to complete the circuits (e.g lighting fittings, socket outlets with usb outlets etc.) - it is easier said than done.


    Perhaps we need to question just what it is we want to achieve.  


    Note that the insulation resistance test as described in BS 7671 (643.3.2) is meant to be applied to the assembled installation, i.e .... "the main switch board and each distribution circuit tested separately, with all its final circuits connected but with  current-using equipment disconnected," ......


    So it is not meant to be a collection of single circuit or part wired circuit tests.


    Disconnecting current using equipment is problematic if that equipment is actually part of the fixed installation (eg socket outlets with usb outlets).


    I don't have any solutions other than to say that perhaps the great and the good should look at the requirements for testing and the type of testing again.


    Regards


    Geoff Blackwell 

     

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  • 0
    That is the advice that was / is given, but how well it is followed is another matter.  It's fine on small installations but on installations with many fittings that need to be connected to complete the circuits (e.g lighting fittings, socket outlets with usb outlets etc.) - it is easier said than done.


    Perhaps we need to question just what it is we want to achieve.  


    Note that the insulation resistance test as described in BS 7671 (643.3.2) is meant to be applied to the assembled installation, i.e .... "the main switch board and each distribution circuit tested separately, with all its final circuits connected but with  current-using equipment disconnected," ......


    So it is not meant to be a collection of single circuit or part wired circuit tests.


    Disconnecting current using equipment is problematic if that equipment is actually part of the fixed installation (eg socket outlets with usb outlets).


    I don't have any solutions other than to say that perhaps the great and the good should look at the requirements for testing and the type of testing again.


    Regards


    Geoff Blackwell 

     

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