Locate Neutrals

Mike2006

I have an issue where I have a commercial building that was originally wired with wires on all the socket circuits as opposed to cables. So I have a box trunking full of neutral wires which are all together (I can’t identify which neutral belongs to which live on each circuit).
My problem is that I have to put all the individual socket circuits on RCBO’s which means I have to match the neutral and lives on each circuit to the individual RCBO.
I cannot be the 1st person to come across this problem.
Is there any piece of test equipment that I can connect either connect to a neutral and it will send a signal down the cable and I can pick it up at the correct neutral cable in the box trunking or at the neutral bar. Or better again, something that I can plug into a socket and it will do the same.

Mike

DublinDilbert

A simple way to do it would be to power every thing down, plug out all appliances & put a resistor (say 1K) in a plug top between the L & N terminals. Pop the plug into a circuit and go back to the fuse board with a multi-meter and see what cables you can see it on.

You could of course just do the above and plug in an incandescent lamp in to the circuit instead of a resistor.

I'm sure a CAT5 cable tracer would work as well.

evosteo

easiset way i reckon would be to first power down everything, then disconnect all the neutrals in the trunking. use your meter and a wandering lead to bell out each individual neutral at each individual socket and you will be able to indentify each individual circuit

M cebee

he doesn't need a wander lead for that

all the final circuits are wired in pvc singles and you can't identify them?

is everything dead?

i'd prob use a tone generator to identify the phase and neutrals
quickly and then confirm

Mike2006

Thanks for the solutions so far.. I reckon I would need a 100m wandering lead to do it though!

I am also looking at just putting an rcd protected socket at each socket point as well. I will price both options anyway.

Thanks,

Mike.

M cebee

stop:pac:


put you're rcd's or rcbo's into the board

are the cpc's marked or anything-they're prob all 'common' now if sockets are fitted and it's steel


is anything marked

how big is the installation -how many final circuits

Bruthal

If you have a grip ammeter and you can get it around each neutral, you can pick a neutral and see it has current going through it. Then proceed through each socket MCB, switching them off and back on until you get the one that cuts off the current in the neutral. Make sure no computers etc are going of course.

If you have already fitted your RCBO`s to the board which would be a help, then connect each live neutral pair you find to an RCBO which will work properly if its the matching pair. But again, verify it by making sure something is working on this circuit and goes off with the RCBO.

Any neutrals which show no current during the initial neutral testing, just plug something into a socket on the circuit, and proceed as above. This should be simple enough once you can get the grip meter around each neutral.

This is one way to do it anyway.
Another way it can be done is every socket neutral into individual connectors with all socket MCB`s off, and turn on just one MCB at a time and find the neutral that now shows as live with a tester. Again something is required to be plugged in on the circuit.

It is easier with radial circuits. If each MCB only has one wire from it then they should be radials.

M cebee

there isn't much to it anyhow-should be very simple

i thought all he had was a ball of wires

if it's an existing installation a good contractor would have them corresponding- bars and mcbs

Bruthal

Yes but you would still have to verify them, not just connect and assume, but your right, it certainly should be like that alright with the neutrals order onto the neutral bar, which would speed up verifying them. Simple enough to sort them anyway.

M cebee

yes-they have to be verified and tested after

won't get too far anyhow with mix-up's and rcbo's-they'll trip