Strange neutral voltage

[CraigF]

Hi all,

Been working on a mitsubishi heavy industries unit today with a e32 fault. The site has a step down transformer so I'm getting around 204v on phases to earth(three phase unit). However, I'm getting 36v at neutral when I turn the isolator on and one phase drops to around 178v. No other units on the site have any issue with the neutral and it's ok at the dis board. I've tried removing all load items from the unit indoor and outdoor, still I have this fault and voltage at the neutral! I've even changed the outdoor board as I've just decommissioned the identical unit next to it and replaced with an RZQ140.

Anyone had anything similar???

Cheers in advance!

CraigF

[install monkey]

bunched cables creating a ghost voltage?

[CraigF]

I have sat and thought that tonight, it's cabled in SY if that makes any difference.

[gsracer]

I think you have lost a phase

[install monkey]

if the sy is run parallel to cable- like in galv trunking with singles then it could pick up interference, run a temporary cable along the floor to prove this- had it on a burner- got 73v neutral to earth- panel was 6mtr away

[Magoo]

Check what voltages you get between phases, all should be the same. The site step down transformer probably does not have a neutral to earth link on the secondary side. So you get weird voltages between neutral and earth, particularly if using a digital multi-meter, try it with an analogue meter. Get a registered electrician to do a loop impedance test to be doubly sure. Also I have had situation that one transformer coil was playing up and needed rebalancing but that generally occurs under load conditions.

[CraigF]

Thanks for the help lads, will update as I make some progress!

[CraigF]

Evening all,

Problem is now sorted. Ran a new cable in which solved the neutral problem(28m down a dry riser mind!!! All good fun!!!) Only to find e32 fault still. Switched a couple of phases and gone!

Thanks for the help lads, much appreciated as always!