1

The following paragraph appears near the end of this article:

Simple three light testers cannot detect two potentially serious house wiring errors: (1) neutral and ground reversed at the receptacle. (2) a bootleg ground, where the neutral and ground pins have been connected together at the receptacle. This may be done by someone fitting 3-prong receptacles on a circuit that has no ground wire. These errors can be detected with a multimeter and a test load, to verify that the ground connection is separate from the neutral and is not carrying normal circuit current.

Would someone please explain how to use a test load with a multimeter to do what's mentioned in the paragraph?

  • The best way is to look. I have not seen neutral and ground reversed in my time as an electrician. A boot leg is where the ground and neutral are connected many times at the outlet when no ground is available. Testing with a meter may not tell if there is a boot leg ground. Measure the voltage from hot to neutral then hot to ground there is usually a difference but this not always true. If you see a voltage measuring neutral to ground it is probably good or bootleged further up. – Ed Beal Feb 24 '17 at 0:20
  • Ran out of time since I hit return oops. Look for 3 wires entering the box 1 bare copper connected to the box if metal or back of the outlet to the green screw. If the bare wire is in one of those positions it would be hard to have them reversed. If you have a much older home tracing the wire to the panel would be the only way to know if it was bootleged someplace. – Ed Beal Feb 24 '17 at 0:29
  • Thanks, @EdBeal. I should have explained that I came upon this when I was doing some editing work on wikipedia. It's not so much that I want to be able to check wiring as that I'd like to understand how this could be done with a multimeter. – Bill Bell Feb 24 '17 at 15:04
2

I'm taking a stab to open the analysis. Based on the wording of the Wikipedia entry the puzzle is to devise a test using a test load and a multi-meter with the cover plate in place. To detect whether the ground is carrying current one would connect a load to one receptacle of a duplex pair and then on the other receptacle measure the voltage difference between the neutral and the ground or the hot and the neutral or ground. If this is a single receptacle one would use a multiplug cord or adaptor. Somehow the results would reveal reversed neutral and ground or bootleg ground.

Another possibility is with the load connected use an extension cord to a known good receptacle. Measure the voltage difference between a good ground and the ground and the neutral on the receptacle under test.

EDIT

The detection of a bootleg ground in a given receptacle seems straightforward. Connect a significant test load (10 to 12 A) and measure the potential difference (voltage) between the neutral and the ground. If they are tied together in the box, the voltage will be close to 0. If the ground and neutral are tied only at the panel, the voltage will be > 1 V to ~ 3 V. I have a simple Fluke tester which will not read less than ~4 V so using that meter I would measure the voltage between the hot and the ground and the hot and the neutral. If these are equal, then there is a bootleg ground.

  • Yes, that's the puzzle. Or at least it's a puzzle for me. Ideally, I would like to be able to find a reference to an analogous circuit that shows how this diagnosis is made. – Bill Bell Feb 24 '17 at 15:07
  • From a main service panel the ground and neutral terminate at the same point so there is truly no way to know if the wires are reversed. By measurement only, Even with a load. I have never seen this but I guess it could happen. – Ed Beal Feb 24 '17 at 15:39
  • When we moved into our tract house 38 years ago I checked the wiring and found one receptacle with the ground and neutral reversed. This was a single receptacle supplied by a 7' Romex cable in metal conduit in the slab. One other circuit was so mis-wired that I could not figure out what was going on. I called the major contractor who had done the wiring and they came out and rearranged the wiring at no charge to me. We were the 3rd or 4th owners of the house which had been built 6 or 7 years before. – Jim Stewart Feb 24 '17 at 21:52
  • I earlier commented a way to tell a reversed neutral and ground from voltage measurements, which I deleted because I now think it wouldn't work. I have a good opinion of Wikipedia and am predisposed to think their suggestion must have merit. To detect a reversed ground and neutral on a particular receptacle it is possible that measurements on the other receptacles in line toward the panel would be diagnostic. If the ground is not carrying current, all grounds in a circuit would be at the same potential. If every receptacle in a circuit has gnd and neut reversed, then this would not work. – Jim Stewart Feb 25 '17 at 0:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.