Clamp meters (for measuring current) are not only useful for fault finding and diagnostics. They are also useful for locating circuits in messy boards, particularly neutrals.
For instance, following an addition or alteration to a circuit, you will want to do an IR test, which obviously requires disconnection of the neutral and line conductors. The line is usually easy, but finding the correct neutral can often be problemmatic, especially if wired in singles, and you're presented with summat like this:
View attachment 31366
View attachment 31367
Yep, there's a neutral bar in there somewhere. No, I'm not allowed to power down half the installation to disconnect the right hand breakers to find it.
Here's how to do it: before you start your addition or alteration, the circuit will presumably be energised. Clamp the line conductor of that circuit, make a note of the reading (say, 2.68A, for lights) - will need a load on, obviously. Now clamp individual neutral cables one at a time, starting with the ones that are the same CSA as the line conductor.
If you get one that reads about the same, then (assuming you have permission to isolate), isolate that circuit. Does the reading go to zero? If yes, you've
probably got the right circuit - although there's still a very small possibility that you've got the wrong circuit, and the load (on another circuit that you've got your clamp meter around) happened to go off at the time you flicked the switch on your intended circuit. So switch it back on again. Does the reading go back up again? Cool. Mark up that cable. Now do safe isolation and do your work.
I'm sure you all know this, but to be absolutely clear: this method (clamp meter) does NOT prove isolation, it only
indicates the likely cable for that circuit. Use the correct instrument(s) to prove dead and follow safe working procedures.
Cheers for posting. 
