I have an older house with old wiring. How can you tell which wire in a 2 wire system is hot?

Question

Both wires are the same color and no ground wire. I am getting ready to rewire my house with three wire system but for now I need to know how to find out which wire is hot. does it even matter? Thanks.

Answer 1

Get one of those screwdrivers that light up when it touches the hot lead. Mark it with black tape, then mark the other with white tape.
You can get another tester with 2 wires. Touch one side to the box (metal) and you touch the other to one of the wires. If it lights, that's the hot one. Then touch the other one and you should not see it light.
1- Tape the hot wire with black tape and the common on with white.
2- In the fuse box, the wire that comes off the fuse is the hot one.
3- In a breaker box, the hot wire comes off the breaker screw.
Have a real electrician do the wiring and make sure he has a license.
If you own your own house, you still need a permit and have the finished work inspected.
Good luck !

Answer 2

First, Yes. It does matter which wire is 'hot' if you want to safely correctly rewire the house.
Second, and this won't be easy, you must find a GOOD ground. If you have galvanized pipe, the cold water pipe would be great. If not, locate the copper rod going into the ground that the phone company uses for ground. If this is not readily available, use the fuse box as ground.
Third, you will need to firmly connect one wire of 12/2 or 14/2 gauge house wire to the ground of choice. The other end of the wire will then be your ground. It will then be a simple matter of using a meter to read from your known, good ground to either side of the outlet. If you read nothing, that wire in the outlet is the ground wire. If you read 120 VAC, that's your hot wire.
Hint: Once you have determined which wire is ground in a certain outlet, you can then use that point for reference on the next outlet. Small nuisance, but you're tackling a BIG job.

Answer 3

Yes. You can buy a plug-in three prong tester with three LEDs that tells you what's wrong or right depending on which ones light up, and the answers are printed on the device. It's a small thing and really cheap. If you only have 2-hole outlets, use one of those 3-hole to 2-prong adaptors that have a wire or terminal for the ground. You don't have to attach the ground for testing, but the device will light up to tell you that you don't have a ground. It will also light up to tell you if the neutral and hot are switched. So if you connect a plug socket to the wires and plug in the tester, it will tell you if the wires are connected correctly or switched. You know which is hot by which is the hot side on the outlet--if it comes up "not switched" (only missing ground) then you know the hot wire is on the proper hot side of the outlet. Or it will tell you that they're switched.

You COULD use the old electrician's trick that was in vogue back when they built houses like this, but I don't recommend it. I include this for a laugh. And amazement. If you are dry and not touching a ground, you'll feel a buzz if you touch the hot wire!

Q: What's gray, smokes and hangs from the ceiling?
A: An amateur electrician.

Be safe.

Answer 4

Old House Wiring

Answer 5

The easiest way is to go to the hardware store and get a tester with a LED sensor that will glow when you bring close to a hot wire. They look like a pen and are inexpensive. With the old knob and tube wiring, it's nearly impossible to tell by looking unless you can trace a circuit back to the fuse box. And then there's the old, tried and true, finger test. 50/50 you get zapped. And, it only matters if you plan on tying into the old stuff. If you're going new all the way, it's no problem.

Answer 6

Go to Local hardware store, they have what is called a non contact voltage tester. You push in on the pocket holder and hold end close to each wire, the tester will light up and many will give you an audible alarm when you touch or get very close to the hot wire but will not do this with the neutral wire.

Answer 7

if you look real good you may see a blk line on the insulation for the hot wire, it will be really faded but it si there i think
the white will be plain white,

the best thing is a gardner tester lowe's home depot , REd in color about 8 bucks keep on with me all the time , you touch a hot wire and it chirps works great. Do tag the wires some how

Answer 8

do NOT use these pen type testers! I've seen more damage done by those who have used them! use a real volt meter. also it scares me to even read your question, much less give you advice... call a qualified and licensed electrician before you get hurt! Odd though since you say your going to"rewire" your entire house.... what does it matter about the OLD wires since your going to cut them all out anyways? Again, sounds like you have no idea what your doing....and to all those who mentined these cheap "testers" YES they can show voltage other than the hot lead....they simply cannot be trusted... and will even show false readings with static electricity...and last question.....you ask "does it matter?" OMG ...Ummmm YES... it certainly does matter!

Answer 9

An inexpensive tool designed for the purpose will tell you. Some look like screw drivers, and some like Pens. while others have two leads and a small light bulb in a plastic enclosure.

What matters is completing a circuit, and "matters" Matters if you happen to have a live wire while standing in a tub or water, and holding it while being grounded,,,smiles,,, DON'T

Rev. Steven

Answer 10

well, if you have a voltage meter, than unhook the wire from the appliance or plug inn and check each wire with the meter to ground,,, be sure power is turned off at breaker before you unhook them,,,and separate wires so they do not touch and then cut power back on,,, if you have an appliance turned on ,,, remember both wire will show hot,,, until separated from appliance,,,hope this helps,,,