Lighting wiring, proving neutral

[gazdkw82]

So I had a tricky little task today. 2 gang 1 way switch in a small office entrance. Controls 2 lights in this area. Customer wanted a sensor to replace the switch so both lights come on when triggered.

Took the switch off and blimey nothing was identifiable. Blues, blacks, reds, browns ,yellows..... Not a single piece of sleeving in sight.

It took me ages to work out what was what.

However, at one point I was trying to prove if any of the blue/black conductors were actually neutrals or not. I linked out R2+RN and tested at the light fitting. I got a reading, however just for clarity I unlinked and tested R2+RN at the fitting and I still got a reading.

I can only imagine that it is due to the fact neutral and earth are effectively the same thing back at the station.

But even though I solved the wiring and all is working it got me thinking. How do you proove neutrals? R1+RN?

 

[westward10]

If it is wired in T&E the presence of blue and yellow often indicates two way switching.

 

[gazdkw82]

Yes I agree. No evidence of it though

 

[SparkyChick]

Probably R1+RN with the link at the board and all loads removed.

Failing that break out the wander lead, disconnect the neutral at the board and go for a wander

 

[gazdkw82]

Could be linked out somewhere

 

[MFS Electrical]

You could turn off the main switch To the whole building and test that way there wouldn’t be a “joint” on the two of them the other way would be to disconnect all the conductors of the circuit at the DB

 

[baldelectrician]

Easier to leave the switches in the on position and put in 2 new sensors (one for each light).
Some times simple is cheaper (in time and money)