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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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  • 0
    Hmm. in your shoes at least verify on, then lock it off,  and then verify it really really has gone off and that no amount of knocking or shaking or waggling the actuator  can posibly turn it back on. The sensors must (should) be on the dead (output) side if it is wired properly.

    May be need to arrange the input terminals covered with something to prevent anything falling into the works if there are long supply side lugs visible that are always live also.

    Not sure if there is a fancy torque setting bolt  - the drawings look like the screws on a new one are longer than when fitted - does a big head shear off at the right setting, to reveal a smaller head only for removal ? Seems overkill if so , but in some way typically Germanic.

    May be better to wait for someone who has used one to respond, I haven't.



    M.
Reply
  • 0
    Hmm. in your shoes at least verify on, then lock it off,  and then verify it really really has gone off and that no amount of knocking or shaking or waggling the actuator  can posibly turn it back on. The sensors must (should) be on the dead (output) side if it is wired properly.

    May be need to arrange the input terminals covered with something to prevent anything falling into the works if there are long supply side lugs visible that are always live also.

    Not sure if there is a fancy torque setting bolt  - the drawings look like the screws on a new one are longer than when fitted - does a big head shear off at the right setting, to reveal a smaller head only for removal ? Seems overkill if so , but in some way typically Germanic.

    May be better to wait for someone who has used one to respond, I haven't.



    M.
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