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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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    I've replaced one of these breakers with the board live still. This was on a new board around 4 years ago, so older ones may be different.

    IIRC, there wasnt anything that worried me about replacing it. I think the busbar bolts are plastic, or I may be thinking of another board, but if it is these, it is a 17mm socket head bolt, I havent got an insulated socket wrench, so probably was plastic.

    None of the other live parts are accessible without a thin screwdriver, you cannot inadvertently put a finger on a live terminal on the modern Schneider large panels.
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    I've replaced one of these breakers with the board live still. This was on a new board around 4 years ago, so older ones may be different.

    IIRC, there wasnt anything that worried me about replacing it. I think the busbar bolts are plastic, or I may be thinking of another board, but if it is these, it is a 17mm socket head bolt, I havent got an insulated socket wrench, so probably was plastic.

    None of the other live parts are accessible without a thin screwdriver, you cannot inadvertently put a finger on a live terminal on the modern Schneider large panels.
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