How about this one

[brizospark]

OK working in a factory at the moment and the wiring is diabolical

Here's one anecdote-

Lighting circuit - lights are on

Take fuse out - lights go out
Fuse in, neutral disconnected - lights go out
fuse out, neutral disconnected - lights on

Work that one out

 

[Bradzz]

Is the system balanced, check the nuetral or earth for voltage.

 

[tony mc]

OK working in a factory at the moment and the wiring is diabolical

Here's one anecdote-

Lighting circuit - lights are on

Take fuse out - lights go out
Fuse in, neutral disconnected - lights go out
fuse out, neutral disconnected - lights on

Work that one out

With the last one( Fuse out Neutral discnnected -lights on ) have you isolated other circuits to find out where the feed is now coming from

 

[topquark]

Serious head on now. Assuming polarity checks for that circuit are OK and no earth/neutral reversal? If they are then it's obviously getting a feed from another source, so the question is via what route.

 

[topquark]

As a first pass I'd be tempted to test each of the line/neutral/cpc for that circuit (after your attempted isolation method) with a clamp meter to see if any of that is still involved in your circuit (as you can do that at the DB/CU easily).

 

[brizospark]

no lights not dim and it aint anything to do wit type of factory

 

[topquark]

Another thought is, are there any contactors/timers that could be switching in the alternate supply to the lights?

 

[brizospark]

It aint nothin to do with pylons im pretty sure!

I think it may be getting a live feed from another 1 of the other 85 boards and that it is picking up its neutral from an earth return

 

[topquark]

How much control do you have over the supplies, IE do you have exclusive use or is the factory up and running?

 

[brizospark]

the factory is running 24/7

No contactor controls

I'm sure its a backfeed / earth return path

Absolute nightmare

Plus on some of the fittings there is 400v

Two supplies at klix roses from different phases honestly never seen anything like it!

 

[topquark]

the factory is running 24/7

No contactor controls

I'm sure its a backfeed / earth return path

Absolute nightmare

Plus on some of the fittings there is 400v

Two supplies at klix roses from different phases honestly never seen anything like it!

Sorry, ducked out for a curry. Well, the fact that there's 400V on the fittings is a clue, you have more than one phase at those fittings (and if they are all individual circuits then you have a mix ... you could do a roation check (from a known phase) and at least work out what the other phase is (that'll cut the nr of circuits in 3). Given that the factory is 24/7 do you have scope to turn all the lighting circuits off?

 

[Goody]

Did anyone here mention borrowed neutral?

 

[hasel5]

you have a neutral problem at some point givng you the 400v so suggest you switch off the board you are working on asap and check all phase connectoens and the neutrals this sounds like a big prob

 

[BlueToBits]

Is this worded to throw us off?
My tenpenceworth:

Sounds like unbalanced 3 phases all with common neutral and your circuit under test is the mid loaded circuit with a high impedance fault L-E (in the order of 20 ohms) could be one or more but not all fittings wired live-earth.
Take fuse out - all lights on that phase go out. Other 2 phases have their own live and the shared neutral and therefore burn OK.
Fuse in, neutral disconnected - all lights on that phase go out - lights under test with the high impedance earth fault are creating a 'virtual' neutral at some voltage sufficient to keep the other lights burning but not themselves.
fuse out, neutral disconnected - lights on. High impedance earth fault providing neutral for all lights. Lights under test are running reversed polarty fed through lights on the other phases.

 

[Deleted member 26818]

View attachment 5682View attachment 5683

It's not only bulbs that go in the ground then.

 

[Bradzz]

Chinese lanterns

It's not only bulbs that go in the ground then.