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Schneider NSX micrologic trip units

Former Community Member
Former Community Member
Had a callout to a block of flats last night where one of these devices (250A) had tripped. Cause seems to be a fault on a lift, as its own 100A downstream device also tripped, so obviously not set correctly for discrimination. Problem is that after restoring the 250A device it now trips on a very small load, literally a couple of amps per phase. Wondered if anyone has seen this before? has the trip unit been destroyed by the fault or has its electronics got into a pickle?


As it was night time there was not enough load to even light the micrologic display. As a temp clear I managed to move the circuit onto an unused 100A device in the panel but for 13 flats and the communals dont know how long ill get away with that.


PS can the trip units be replaced safely on these units without isolating the upstream device, this would be a 1600A ACB feeding a very large development.


Thanks in advance


Tom
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    John Peckham:

    Geez


    Have a look at this https://www.youtube.com/watch?v=_VWaytGcAxU


    The cautionary notice, which whizzes by at the beginning says work dead. It's all very well demonstrating the process on a work bench where uninsulated tools present no hazard, but the lower terminals seem to be exposed during this process. If they are on the load side, that may be an acceptable risk.


    Switching off a whole block of flats for a few minutes may be a nuisance, but bear in mind R.14 of EAWR 1989!


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  • 0
    John Peckham:

    Geez


    Have a look at this https://www.youtube.com/watch?v=_VWaytGcAxU


    The cautionary notice, which whizzes by at the beginning says work dead. It's all very well demonstrating the process on a work bench where uninsulated tools present no hazard, but the lower terminals seem to be exposed during this process. If they are on the load side, that may be an acceptable risk.


    Switching off a whole block of flats for a few minutes may be a nuisance, but bear in mind R.14 of EAWR 1989!


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