I have an older home where BOTH wires in the Romex are black (instead of the normal black and white). I screwed up - took a receptacle out to replace it and failed to mark which was to the silver (common / white) side and which was to the brass (hot) side. How can I NOW figure out which was which? I tried my volt meter... figuring ONE way would show 120 POSITIVE and the other 120 NEGATIVE volts. Nope - both showed up as positive numbers. Any Ideas???
Mr. E
Favorite Answer
use your volt meter and check each wire to ground, one will show 120 and the other will show 0.
it's him
There is no direct negative or postive current in a homes electrical wiring. It alternates at 60 cycles from positive to negative. There should be 3 wires going to each receptacle, a hot, a ground and a neutral. Hardware stores sell a simple test pen that allows you to touch each wire seperatly to help determine the hot from the ground. When working on anything electrical, such as this, you should down the electric system to avoid serious accidents.
Do-It-To-Yourselfer
You most likely have "knob and tube" wiring, and if both leads are reading a voltage there has probably been a little unauthorized work done on the system.
More than likely, it might be time to have the outlet looked at by a pro. There is a chance that the stray voltage in the neutral leg is the cause of the outlet needing replacing, and this voltage may injure someone in the future who wasn't as careful as you.
dtstellwagen
Those inductive test pens are neat, but in my experience nothing beats connecting one lead to an actual ground (an iron or copper water pipe) and test the wires one at a time. In the process of trying to do this you may find that the house service isn't grounded/bonded to todays standards (ground rods, bonding of hot and cold water) and although no requirement exists to upgrade systems that were legal at the time of installation, there are benefits of having a good ground system and you may find this is a good time for improvement.
What is going on
Make sure your meter is set to AC (a wavy line). Don't try to measure the voltage on bare wire dangerous. Install the plug. It's OK if it backwards for now as long as nothing is plugged into it.
Then measure from one slot to ground. Then measure the other slot to ground. You'll know which one is hot and which is neutral. Mark it then look how you hooked it up. You are correct gold - hot silver - neutral.