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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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    Geez:

    It is a 5.2E unit so no earth fault protection and the faulty lift is still isolated. I can reset the device with no load, then as I start turning on the isolators to the 13 flats it trips after I get 5 or 6 on, any 5 or 6 so not a fault in one of them just when there's enough load, which was less than 20A across all the phases according to my clamp meter.


    I can not read and digest all of the maker's instructions, but I wonder if the unit has defaulted into some kind of protective mode to prevent being reconnected onto a fault? It may not be faulty at all.  I would contact the maker's technical dept. and ask them. The unit is very complicated and the maker's are the ones to diagnose the problem. It is just a matter of grasping the nettle and making progress here.


    Z.


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  • 0
    Geez:

    It is a 5.2E unit so no earth fault protection and the faulty lift is still isolated. I can reset the device with no load, then as I start turning on the isolators to the 13 flats it trips after I get 5 or 6 on, any 5 or 6 so not a fault in one of them just when there's enough load, which was less than 20A across all the phases according to my clamp meter.


    I can not read and digest all of the maker's instructions, but I wonder if the unit has defaulted into some kind of protective mode to prevent being reconnected onto a fault? It may not be faulty at all.  I would contact the maker's technical dept. and ask them. The unit is very complicated and the maker's are the ones to diagnose the problem. It is just a matter of grasping the nettle and making progress here.


    Z.


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