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  1. #1
    Join Date
    Oct 2014
    Posts
    1

    Default 2 lights in backyard not working

    Hi,
    I have been doing some electrical work in the garage in my backyard to add a switch and more lights. I had to do some re-wiring and now there is something that is not working.

    the garage has 2 underground cables that are powered by the same breaker Inside the house). 1 of the 2 cables is controlled by a simple switch inside the house. The first cable (let's call it A) powers the garage and does not have any problem. The second cable (let's call it B), that is controlled by the switch in the house, powers 2 separate circuits: a garden pole (B1) and a light fixture on the steps on the side of the garage (B2).

    to do my tests I am using a Klein Dual Range Non-Contact Voltage Tester (simple device) http://www.kleintools.com/catalog/el...voltage-tester.

    when the breaker and the switch are on, but the 2 circuits (B1 and B2) are not connected, I can test the voltage on cable B (which, by the way, is an old wire; like the ones that run inside flexible metal conduits and are covered by something that seems like a cotton tread rather than plastic). during the test, I hear a very fast beep if i touch one of the 2 cables and a not-so-fast beep if touch the other wire of the same cable (B).

    after i connect any of the 2 circuits (either B1 or B2 with black, white and naked wires.. more modern), both wires seem to be loaded because they have the same "very fast" beep when I touch them with the tester.
    The lights do not work.

    bottom line, it seems that both wires are hot only after i connect any of the 2 loads.

    what can it be?

    thank you.

  2. #2
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,808

    Default Re: 2 lights in backyard not working

    First you need a volt meter, non contact testers are terrible unreliable and often give false indications.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  3. #3
    Join Date
    Jan 2014
    Location
    El Paso, TX
    Posts
    34

    Default Re: 2 lights in backyard not working

    Ditto on the volt meter. Also sounds like you might have a bad neutral connection but get the volt meter.

  4. #4
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,631

    Default Re: 2 lights in backyard not working

    Also watch out for a condition known as reverse polarity bootleg ground (RPBG).

    First, let's go over what a bootleg ground is. Old wiring exists that doesn't have a ground wire. So Joe Homeowner wants to add a grounded outlet. Since there is no ground wire, he puts a jumper between the neutral wire and the ground screw on the outlet. If you plug in a typical three-light outlet tester, it will show that everything is good. If you meter it, you will measure 120V between hot and neutral, and 120V between hot and ground. But here's the kicker: if you meter between neutral and ground, you will get exactly 0.0V. In a normally grounded system, you should measure a few volts between neutral and ground due to the wire resistance, existing loads, and inductance. (If the ground has been bootlegged somewhere upstream, there may be some voltage difference between neutral and ground. Measuring 0.0V is an indication of a bootleg ground, but it shouldn't be considered the definitive test.)

    With a RPBG, Joe Homeowner got mixed up when he installed the outlet, and swapped around the neutral and hot, or maybe the wiring is mixed-up upstream of that point. Either way, the hot wire ends up getting connected to the wide slot of the outlet, and the neutral ends up connected to the narrow slot. But Joe still installs the jumper between the wide slot and ground, because he THINKS he's hooked the neutral up to the wide slot. Now here is the big problem: it will test EXACTLY THE SAME as in the last paragraph -- in other words, everything tests OK. An RPBG is very dangerous, as now the chassis of a metal appliance can become charged with 120V.

    The only way to properly discover an RPBG is to measure the voltage between each conductor and a known good ground, such as an extension cord plugged into an outlet you've determined is wired properly.

    More info on RPBG here:
    http://www.rvdoctor.com/2001/07/frie...gary-mike.html
    http://forums.mikeholt.com/showthread.php?t=146019
    http://www.youtube.com/watch?v=XfAPkJVYUpY

    Most people have learned that the black wire goes to the brass screw, and the white wire to the silver screw. I don't follow that convention ever since I found an outlet that came from the factory with the screws reversed. I always wire according to the slot size or position instead of the color of the screw.
    Last edited by Fencepost; 10-17-2014 at 12:26 PM.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

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