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I was sent to a building as there were no lights in the lift motor room at the top... Got there, opened 2 x fluorescents and tested for voltage at them and it showed 400v, opened the light switch... got the same... So my initial thought was i had lost a neutral somewhere...
The lift motor room is supplied from a Distribution Board, the three phases come from the DB to a switch isolator, from there it goes to another switch isolator before finally going in to the Board at the top.
So I went to the local fuse board in the motor room ( 3 banks of 4 fuses, each supplied by a separate phase) isolated the board, pulled the appropriate fuse, re-energised board and tested at incoming end, again, 400v between phases, 400v between each phase to neutral, same to earth and 240v between neutral and earth.
So then i'm thinking ok, I've lost a neutral and it's shorting to earth somewhere, traced every single cable associated with that board and the supply for it, no obvious fault anywhere... Went back and re-isolated the board thinking I must have missed something, pulled every single fuse in the board and went to test again, this time i got 0v across the entire board between phases and to neutral and earth.
Eventually I narrowed it down to a particular circuit on the blue phase, when it doesn't have a fuse in it, the board is dead, however when it's got a fuse in it, the entire board reads 400v and 240v between neutral to earth... I've traced that circuit to a dead end looking for some sort of fault on it, Disconnected everything associated with it looking for any sort of fault to cause that amount of overload and... Nothing?
Basically hoping someone may have came across something similar and can point me in the correct direction?
The lift motor room is supplied from a Distribution Board, the three phases come from the DB to a switch isolator, from there it goes to another switch isolator before finally going in to the Board at the top.
So I went to the local fuse board in the motor room ( 3 banks of 4 fuses, each supplied by a separate phase) isolated the board, pulled the appropriate fuse, re-energised board and tested at incoming end, again, 400v between phases, 400v between each phase to neutral, same to earth and 240v between neutral and earth.
So then i'm thinking ok, I've lost a neutral and it's shorting to earth somewhere, traced every single cable associated with that board and the supply for it, no obvious fault anywhere... Went back and re-isolated the board thinking I must have missed something, pulled every single fuse in the board and went to test again, this time i got 0v across the entire board between phases and to neutral and earth.
Eventually I narrowed it down to a particular circuit on the blue phase, when it doesn't have a fuse in it, the board is dead, however when it's got a fuse in it, the entire board reads 400v and 240v between neutral to earth... I've traced that circuit to a dead end looking for some sort of fault on it, Disconnected everything associated with it looking for any sort of fault to cause that amount of overload and... Nothing?
Basically hoping someone may have came across something similar and can point me in the correct direction?
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