# How to figure out six wires and which goes with which?

• 05-14-2013, 03:07 PM
Homeownerinburb
How to figure out six wires and which goes with which?
I'm going to be replacing an old surface mounted 100amp combination panel that replaced a much older panel many years ago.

The owner tells me that the house is wired with cloth and rubber, but all the wire in the panel looks to be at least tw or possibly even thhn.

Now that the code demands that we tie the handles of circuits that share a neutral, I am scratching my head. In two places circuits leave the panel with four hots and two neutrals.

I don't have the first clue as how to figure which are the hots that go with the particular neutral.
• 05-14-2013, 04:17 PM
leejosepho
Quote:

Originally Posted by Homeownerinburb
In two places circuits leave the panel with four hots and two neutrals.

So, you have 8 hots and 4 neutrals to sort out?

I would first number the hots, then turn them all off and turn them back on one-at-a-time to figure out where each one goes and get that all written down. For example:
1) bathroom light
2) bedroom #1 outlets
etc.

After that, I would turn them all off once again and disconnect all hots and neutrals to be checked and matched. At that point, I would check all the loose wires to be sure no stray voltage is coming back through any of them, and then I would begin checking for continuity to see which hots are related the which neutrals.

If you are not absolutely certain of being able to do all of that in complete safety, hire an electrician who can.
• 05-14-2013, 07:32 PM
ActionDave
Good answer leejosepho. One must be careful there are no cross neurtal contamination. To check for that you would use an amp-meter while the circuits are energized.
• 05-15-2013, 11:56 AM
Homeownerinburb
Quote:

Originally Posted by ActionDave
Good answer leejosepho. One must be careful there are no cross neurtal contamination. To check for that you would use an amp-meter while the circuits are energized.

One of the jobs that clips over the wire, a non-contact?
• 05-15-2013, 11:58 AM
Homeownerinburb
Quote:

Originally Posted by leejosepho
So, you have 8 hots and 4 neutrals to sort out?

I would first number the hots, then turn them all off and turn them back on one-at-a-time to figure out where each one goes and get that all written down. For example:
1) bathroom light
2) bedroom #1 outlets
etc.

After that, I would turn them all off once again and disconnect all hots and neutrals to be checked and matched. At that point, I would check all the loose wires to be sure no stray voltage is coming back through any of them, and then I would begin checking for continuity to see which hots are related the which neutrals.

If you are not absolutely certain of being able to do all of that in complete safety, hire an electrician who can.

Label all the wires so that I can put it back together the way it started.....

Disconnect everything.

Leave all the lights in the house on (to ensure a path from the hot to the neutral).

And look for continuity?

I should also find continuity between the hots sharing a neutral, yes?
• 05-15-2013, 03:44 PM
leejosepho
Quote:

Originally Posted by Homeownerinburb
Label all the wires so that I can put it back together the way it started.....

I was thinking more of knowing where they go so you can later plug something in to assure continuity if you have a circuit or two only feeding outlets.

Quote:

Disconnect everything.
Everything you want to test, then check for stray voltage coming back from anywhere just to be sure you do not get electrocuted when you begin grabbing wires.

Quote:

Leave all the lights in the house on (to ensure a path from the hot to the neutral).

And look for continuity?
Yep, you have the idea going on there.

Quote:

I should also find continuity between the hots sharing a neutral, yes?
No, I think not unless something somewhere is meant to be getting 240VAC.
• 05-15-2013, 09:46 PM
Homeownerinburb
Quote:

Originally Posted by leejosepho

No, I think not unless something somewhere is meant to be getting 240VAC.

I'm pretty sure that if two incandescent lights are on either side of the phase, sharing a neutral, and I have disconnected the neutral and the hots, that I will find a path down one hot, thru a filament, to the neutral, to the other filament, and down the second hot.

Thanks for the tips! I am much less awed by the process now.
• 05-15-2013, 10:44 PM
ActionDave
Quote:

Originally Posted by Homeownerinburb
One of the jobs that clips over the wire, a non-contact?

Yes, a clamp on ammeter is the best way to check. With only one half of a three wire circuit heated up the amps on hot and noodle should be the same. With both hots on and a load on both A and B the amps may be different but the amount of difference should be on that circuits noodle. You may find a few tenths of an amp difference.

Quote:

Originally Posted by Homeownerinburb
I'm pretty sure that if two incandescent lights are on either side of the phase, sharing a neutral, and I have disconnected the neutral and the hots, that I will find a path down one hot, thru a filament, to the neutral, to the other filament, and down the second hot..

Correct.
• 05-16-2013, 04:11 AM
leejosepho
Quote:

Originally Posted by Homeownerinburb
I'm pretty sure that if two incandescent lights are on either side of the phase, sharing a neutral, and I have disconnected the neutral and the hots, that I will find a path down one hot, thru a filament, to the neutral, to the other filament, and down the second hot.

I had not thought of that, and the same could happen with a warm refrigerator on one circuit and a clock on another. So, you might have to unplug a lot of stuff to be able to sort all of this out. If I were the one doing this, I would want to see continuity only between hots and neutrals.
• 05-16-2013, 04:34 AM
jwelectric
Use an ammeter and be safe.

With every breaker in the panel off pick a neutral then start turning on breakers one at a time. This will tell you if the neutral shares two breakers.

Disconnecting the neutral is a bad idea especially if there is electronics connect to the circuit as electronics do not like being in a 240 volt series circuit.
• 05-16-2013, 10:01 AM
Homeownerinburb
Quote:

Originally Posted by jwelectric

Disconnecting the neutral is a bad idea especially if there is electronics connect to the circuit as electronics do not like being in a 240 volt series circuit.

You speak wisdom, Obi Wan. Actually, not much that is designed for 120v much likes 240v.
• 05-16-2013, 04:39 PM
hj
There is a lot more designed for 110/120v than there are 220/240v. BUT, if there are devices on both legs of a shared neutral, and you disconnect the neutral it will ALL revert to 220/240 and destroy anything that is not "balanced".
• 05-17-2013, 08:38 AM
Homeownerinburb
Quote:

Originally Posted by hj
There is a lot more designed for 110/120v than there are 220/240v. BUT, if there are devices on both legs of a shared neutral, and you disconnect the neutral it will ALL revert to 220/240 and destroy anything that is not "balanced".

Yes, "I've seen 'em blow!"

Especially back in my film electrician days, which is all about temporary power distribution. That stuff was hairy.
• 05-17-2013, 10:37 AM
hj
My first experience with it was when I disconnected a water heater and the system was "grounded" through the hot side because they had a failed neutral. Disconnecting the cold water supply line discontinued the power flow through the ground and burned out EVERYTHING, (radios, TV, light bulbs, etc.), which was turned on was trashed. I had to carry a console TV out of the house because it was smoking.
• 05-17-2013, 01:12 PM
Homeownerinburb
Quote:

Originally Posted by hj
My first experience with it was when I disconnected a water heater and the system was "grounded" through the hot side because they had a failed neutral. Disconnecting the cold water supply line discontinued the power flow through the ground and burned out EVERYTHING, (radios, TV, light bulbs, etc.), which was turned on was trashed. I had to carry a console TV out of the house because it was smoking.

Bet that cut into your profit.