Using voltmeter to determine which of the two wires is hot.?

Question

I have two white wires sticking out of my ceiling. on the directions of my voltmeter it says: to determine which wire is hot on either two wire or three wire AC outlets touch the black probe to the ground wire and the red probe in the alternate wires. If the ground wire is properly grounded and the red probe is attached to the hot wire, the voltmeter will glow. The problem is, however, that i do not have a ground wire to do this. What should i do now?

Answer 1

This is AC, think of both as hot. You will need both wires for any appliance like a light, it will not matter which way you hook them up. Touch the probe to the two wires it will light up if the wires are connected at the breaker and it is not tripped. Of course if the wire are connected to a switch it must be on.

Answer 2

Wiring A Voltmeter

Answer 3

First thing to do is to check the voltage between the two white wires. One may be hot and the other nuetral or grounded. That's just to make sure which wire is safe to touch.

To test the electrical potential to ground, just take an extention cord that has three prongs, and plug it into an outlet that has a ground plug. Use the ground opening on the female end of the extension cord to measure the potential of the two white wires relative to ground.

Now here is more information than you might want to know....

The industry standard for home wiring is that the black wire is always hot, the white wire is neutral, and ground wires are generally uninsulated copper. The only place you will see a red wire is when you are working with a 220 volt two phase circuit...like a clothes dryer or electric stove.

It is not uncommon for a contractor to save money by useing wire of the same colors to wire an electrical outlet. They make money by cutting corners.

So check each of the white wires to ground with the extension cord and then label the hot wire with a piece of tape.



If both wires have have no electrical potential relative to ground, they may have a switch associated with them, or they could be part of a three way switch where two wall switches control the same light.

I've attached a link to a site that explains three way switches.

Answer 4

Charles is actually right, when you touch the wires together it should complete a circuit. I'm taking it there is a switch attached that operates the fixture that was there? if there is turn it on, touch both wires with the volt meter it glow. Turn off the switch and try again, should be off. Just reconnect your new fixture(taking it your replacing it) to the wires, either way because they are acting as travelers in the circuit
but as far as why you dont' have a ground that could be several reasons, the age of house or incompetent installer to start with.

Answer 5

You could try using the box as a ground or the bare wire that is in the same cable with the two wires.

Alternatively there is a voltage detector tool which buzzes when it comes near a hot wire. It is about $15 and will come in handy many times.

When you do find the hot white wire put some black vinyl tape on it to make it clear for next time which is hot wire.

Answer 6

OK, here what you do. Take an extension cord and plug it into the wall. I hope you have a 3 prong wall plug so this easy to understand and a 3 prong extension cord with 3 holes. Plug the red lead into the left slot with one hole left one hole down like looking at a face. Then plug the black into the right slot. It should light. Then plug the black lead into the round hole, it should light. Now, with the black lead in the right slot or the hole touch the red lead to one of the white wires. The one that lights is the hot. Hope you understand what I saying.

Answer 7

you need a reading of 123, this will tell you, hey we have power,. 110 volts,
as with lighting . you don't need a ground,

white is hot , always .
i use , an old light fixture to test ,over head ,wires,very fast ,and easy er

Answer 8

don't listen to them you can get shocked? with two white wires someone ridged it up wrong you need to abandon those wires and run new wires to the breaker box good luck
Tom

Answer 9

charles c is gonna get you killed