Sparkingchip:MrJack96:
there is a DB board fed from a centre tapped transformer only on single pole breakers. The board feeds instrumentation. Is there any issue changing it to 110v and tie the neutral to earth there is no socket outlets fed on this so can’t see it as an issue?
How can you tie the neutral to earth?
I must be missing something here, because the obvious answer is "with a bit of green and yellow stripy wire".
Make sure that the centre tap of the transformer is disconnected from the supply earth. Pick one leg of the transformer and call it "neutral". Connect it to the supply earth.
Whether or not it's a good idea to do that is another matter entirely.
MrJack96:
So I don’t have to get a new transformer for the installations? I’ve never seen a centre tapped transformer feeding a distribution board before.
You must have - pretty well every building site has one - along with most school lab areas
The give away is DP circuit breakers
Regards
Sparkingchip:
Go and get a centre tapped site transformer and, so long as your loop tester is okay at 55 and 110 volts, stick the test probes into the outlet socket and do some loop tests L1-E and L2-E.
Then disconnect the circuit protective conductor on the 240 volt supply side and try again.
Disconnecting the earth on the input side doesn't make any difference, as the 110 volt earth loop starts at the transformer and is merely referenced to the earth on the 240 volt side (or 415 volt side).
is there enough oomph! in the circuit to take out a MCB if there is a dead short?
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