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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
    Geez:

    Chris


    Its not just a block of flats, its a large building network and these devices are way before any metering. Basically DNO transformer to my 1600A ACB in switchboard, switchboard busbars to 9x MCCB's (mixture of 400's and 250's) these feed the Ryefields to 7 blocks of flats and 2 retail units. The Ryefields in each block feed the communals of the block and EVERY flat. So my faulty 250 is directly connected to the ACB and feeds one block of flats (communal and flats). The only way I can isolate the 250 is by opening the 1600. If I can safely swap out trip unit it avoids isolating the other 6 blocks and 2 retail units.


    John


    I watched all those vids and spoke to Schneider before posting this but I missed the comments you mentioned, real pity the Schneider guy didn't answer the one about the 40A device tripping on low load when set to 28A, similar to my fault but mine is set to full (250A)


    So, a chain is only as strong as its weakest link. It appears to be a poorly designed installation.


    Z.


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  • 0
    Geez:

    Chris


    Its not just a block of flats, its a large building network and these devices are way before any metering. Basically DNO transformer to my 1600A ACB in switchboard, switchboard busbars to 9x MCCB's (mixture of 400's and 250's) these feed the Ryefields to 7 blocks of flats and 2 retail units. The Ryefields in each block feed the communals of the block and EVERY flat. So my faulty 250 is directly connected to the ACB and feeds one block of flats (communal and flats). The only way I can isolate the 250 is by opening the 1600. If I can safely swap out trip unit it avoids isolating the other 6 blocks and 2 retail units.


    John


    I watched all those vids and spoke to Schneider before posting this but I missed the comments you mentioned, real pity the Schneider guy didn't answer the one about the 40A device tripping on low load when set to 28A, similar to my fault but mine is set to full (250A)


    So, a chain is only as strong as its weakest link. It appears to be a poorly designed installation.


    Z.


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