Electrical question

Christof · « **on:** 18 Dec 2008, 12:59 am »

If I run 4 identical wires, labeled 1-4 on one end, through a length of conduit and forget to label the other ends first, how do I go about determining which wire is which, without pulling them back out?

Thanks
C.

BradJudy · « **Reply #1 on:** 18 Dec 2008, 01:17 am »

Pick two wires, attach a battery to them, test the other end to find which ones have a voltage between them. Or, just twist them together and check for resistance, but this will take a few more trials to differentiate the wires - in the first example, the battery polarity lets you know which is which.

Christof · « **Reply #2 on:** 18 Dec 2008, 01:41 am »

Can I do this somehow with my volt ohm meter?

Don_S · « **Reply #3 on:** 18 Dec 2008, 01:53 am »

Quote from: Christof on 18 Dec 2008, 01:41 am

Can I do this somehow with my volt ohm meter?

Yes, Set the meter for resistance. It will then basically be a continuity tester using its internal battery. Twist two wires together on one end then test the other end (in pairs) with the meter. If there is no reading then you do not have the correct pair. Of course that will only identify a pair of wires it won't tell you which is which on the other end. You will have to try different combos to figure that out. Before you start mark each wire so you can keep track of what you did---this time.

After you identify the first pair the second pair is easier.

Have fun and good luck.

Christof · « **Reply #4 on:** 18 Dec 2008, 02:04 am »

Thank you.

Don_S · « **Reply #5 on:** 18 Dec 2008, 02:20 am »

Forgot to mention that some meters actually have a separate continuity setting. Mine has an audio signal that lets me test without looking at the meter.

Of course resistance (ohms) setting works just as well. No continuity equals infinite resistance and no reading.

CSI · « **Reply #6 on:** 18 Dec 2008, 02:28 am »

If you're stuck without a meter and you have a speaker handy (and are close to it or have an accomplice in the other room) attach any two wires to the speaker terminals and then hold one end of a wire at the other end to the base of a small battery (even a AAA will work fine) then brush each of the other three wires across the + terminal until you hear a sound in the speaker (it will be surprisingly loud). It's trial and error but you'll figure out the matching pairs fairly quickly. I've seen custom installers do this using the rechargeable battery pack on their electric screw guns.

Glen B · « **Reply #7 on:** 18 Dec 2008, 04:24 am »

If the conduit is metallic, clip the conductor of each wire one at a time to one end of the conduit and check each wire for continuity with the conduit at the other end. You can quickly identify each wire that way and mark it off.