Trace knob and tube circuits

[Jman2012a]

I am planning to install an arc fault breaker on a knob and tube wired circuit. I have installed the arc fault breakers on a sub panel that is wired with romex, which was easy to pair the same circuit hot and neutral together. Since I need to pair the hot and neutral together with the knob and tube, does anyone have any advice on how to identify the neutral that should be paired with the hot? It is all like spaghetti coming into the panel.

 

[Jadnashua]

If the circuit has a receptacle, you could pick up an inexpensive acv tracer tool. It has a device you plug into the receptacle and a receiver you use to sniff out the other end. I do NOT know if it can identify both the hot and neutral, but I think it does. You'd want to find the manual and check it out or call the manufacturer of the one you are interested in prior to purchase.

 

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[Jman2012a]

Thank you for the reply, which rang a bell in my head. I will use my continuity test feature on my multimeter, not sure why I did not think of that before. Just have to power down the system and test to find the pair.

 

[Jadnashua]

That will require you to unplug things and disconnect at the box, but can work. The circuit locator device inserts a radio frequency signal into the wire, and the radio receiver can then be used to trace the wire, both through the wall and at the ends. With hard-wired things, it may be difficult to identify which pair is the one, since it's often really hard to get a lead from one end to the other. It can make it easier if you insert a jumper wire in a receptacle to short between the hot and neutral (YOU MUST TURN THE POWER OFF FIRST!), and then, you're looking for a dead short. But, something like a lightbulb and a long wire run could look like close to a short. The RF tester is probably the easiest tool for this sort of thing. This is the sort of thing I was talking about
http://www.homedepot.com/p/Extech-I...eaker-Finder-Receptacle-Tester-CB20/205556925

you can find them for a lot less, but this should be readily available locally if you don't want to go online for something. You might be able to rent one, I've never looked.

 

[hj]

Since ALL the neutrals are tied to the same bus bar at the panel, you will NOT be able to identify the mate to your "hot" wire, unless you disconnect all of them test them individually.

 

[Jman2012a]

In the end I wanted to identify all pairs that are coming in so future upgrades (GFCI or Arc Fault) or a rewire of certain circuits is easier. So I went through the long process of disconnecting all knob and tube wires and then marking them as pairs using the continuity test.