(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 15 of 15

Thread: How to figure out six wires and which goes with which?

  1. #1
    DIY Senior Member Homeownerinburb's Avatar
    Join Date
    Jan 2012
    Location
    Los Angeles, CA USA
    Posts
    505

    Default 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.

  2. #2
    DIY scratch-pad engineer leejosepho's Avatar
    Join Date
    Nov 2006
    Location
    200 miles south of Little Rock
    Posts
    2,474

    Default

    Quote Originally Posted by Homeownerinburb View Post
    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.
    "Great minds discuss ideas, average minds discuss events and small minds discuss people." --Eleanor Roosevelt

  3. #3
    Electrician ActionDave's Avatar
    Join Date
    Feb 2009
    Location
    Colorado
    Posts
    331

    Default

    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.

  4. #4
    DIY Senior Member Homeownerinburb's Avatar
    Join Date
    Jan 2012
    Location
    Los Angeles, CA USA
    Posts
    505

    Default

    Quote Originally Posted by ActionDave View Post
    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?

  5. #5
    DIY Senior Member Homeownerinburb's Avatar
    Join Date
    Jan 2012
    Location
    Los Angeles, CA USA
    Posts
    505

    Default

    Quote Originally Posted by leejosepho View Post
    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?

  6. #6
    DIY scratch-pad engineer leejosepho's Avatar
    Join Date
    Nov 2006
    Location
    200 miles south of Little Rock
    Posts
    2,474

    Default

    Quote Originally Posted by Homeownerinburb View Post
    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.

    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.

    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.

    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.
    "Great minds discuss ideas, average minds discuss events and small minds discuss people." --Eleanor Roosevelt

  7. #7
    DIY Senior Member Homeownerinburb's Avatar
    Join Date
    Jan 2012
    Location
    Los Angeles, CA USA
    Posts
    505

    Default

    Quote Originally Posted by leejosepho View Post


    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.

  8. #8
    Electrician ActionDave's Avatar
    Join Date
    Feb 2009
    Location
    Colorado
    Posts
    331

    Default

    Quote Originally Posted by Homeownerinburb View Post
    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 View Post
    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.

  9. #9
    DIY scratch-pad engineer leejosepho's Avatar
    Join Date
    Nov 2006
    Location
    200 miles south of Little Rock
    Posts
    2,474

    Default

    Quote Originally Posted by Homeownerinburb View Post
    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.
    Last edited by leejosepho; 05-16-2013 at 04:15 AM.
    "Great minds discuss ideas, average minds discuss events and small minds discuss people." --Eleanor Roosevelt

  10. #10
    Electrical Contractor/Instructor jwelectric's Avatar
    Join Date
    Jun 2007
    Location
    North Carolina
    Posts
    2,523

    Default

    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.

  11. #11
    DIY Senior Member Homeownerinburb's Avatar
    Join Date
    Jan 2012
    Location
    Los Angeles, CA USA
    Posts
    505

    Default

    Quote Originally Posted by jwelectric View Post

    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.

  12. #12
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Location
    Cave Creek, Arizona
    Posts
    25,687

    Default

    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".
    Licensed residential and commercial plumber

  13. #13
    DIY Senior Member Homeownerinburb's Avatar
    Join Date
    Jan 2012
    Location
    Los Angeles, CA USA
    Posts
    505

    Default

    Quote Originally Posted by hj View Post
    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.

  14. #14
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Location
    Cave Creek, Arizona
    Posts
    25,687

    Default

    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.
    Licensed residential and commercial plumber

  15. #15
    DIY Senior Member Homeownerinburb's Avatar
    Join Date
    Jan 2012
    Location
    Los Angeles, CA USA
    Posts
    505

    Default

    Quote Originally Posted by hj View Post
    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.

Similar Threads

  1. Can someone help me figure out the problem?!?!
    By danreg99 in forum Irrigation / Sprinkler Forum
    Replies: 1
    Last Post: 05-14-2013, 11:46 AM
  2. trying to figure out pex fitting manufacturer
    By Rocketdoctor in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 7
    Last Post: 04-10-2009, 05:35 PM
  3. Please help me figure this out!
    By mrsjulie in forum Toilet Forum discussions
    Replies: 5
    Last Post: 04-01-2009, 01:10 PM
  4. Can't figure this out! Need some elec. know-how
    By stockwatchn in forum Electrical Forum discussion & Blog
    Replies: 5
    Last Post: 02-01-2009, 12:03 PM
  5. Trying to figure out what is causing water hammer?
    By jmichaelyoung in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 2
    Last Post: 07-28-2005, 09:59 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •