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Old 04-02-2013, 12:51 AM   #1
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?


Just moved into an old house and I'm installing some timer switches for the exterior lights that say they need proper polarity in the manual. that being said every wire in the house is black. There are also no grounds so touching the ground on the multimeter is having no luck. I know nothing about electricity and just want to get these installed

I had one idea. I can run an extension cord from another room. Could I do this and use the neutral from the extension cord to check for the hot wire in the switch receptacle? I also thought about just literally plugging the extension cord into the ground outside to get a ground line but I didn't know if that was safe. Any help would be greatly appreciated!

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Old 04-02-2013, 12:55 AM   #2
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?


I think others will agree but you really should hire a proffesional. From what you describe, you dont have the knowledge of electricity to attempt this.

I thought I knew alot until I came here and these guys corrected me on some things and I have learned alot from them.

Rick

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Old 04-02-2013, 12:58 AM   #3
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?


Thanks, I actually had some electricians come out and run a new main to the house. Unfortunately, I don't have anymore money, at the moment, to hire an electrician. That being said, this is one single pole switch, I just need to know which wire of the two is hot and my problem is solved. Thanks for the input though!
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Old 04-02-2013, 01:01 AM   #4
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?


Quote:
Originally Posted by fuzzbutter View Post
Just moved into an old house and I'm (attempting to) installing some timer switches for the exterior lights that say they need proper polarity in the manual. that being said every wire in the house is black.
Almost NO older home will have that "proper polarity" at the switches.
It's just not there. Find a different timer or plan to rewire the whole circuit.

Quote:
I just need to know which wire of the two is hot and my problem is solved.
They're both hot... it's called a switch leg.
---

As to both wires being black... are you in the Chicago area?
If you have conduit...
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Old 04-02-2013, 01:37 AM   #5
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?


Thanks Tarheel. Let me clarify all the information I have so far. There are some things I left out that I thought wasn't important but maybe they will help. Maybe not.

I installed the switch earlier today and it worked fine for a few hours but after reading on the internet a little more I saw where people said that even single pole switches need to be setup properly (i assumed that was called polarity maybe I'm wrong) so I uninstalled the switch and went out and bought a multimeter so I could make sure they were right. Anyway that being said, below is a link to the switch I bought as well as an image of the instructions and a pic of the receptacle. After taking the switch out and moving some wires around I did notice a white wire going up the back. The two black wires are wrapped differently as well. One is cloth and one is plastic. I'm really trying to find a solution in the next 2 days before I leave town for 2 months (which is the reason I bought these in the first place). Any help would be greatly appreciated. I may just have to throw the old single pole switch in there. Thanks again!

The switch: http://goo.gl/F9MyG

The pic:
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Old 04-02-2013, 01:48 AM   #6
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?


Is this a SP switch? (I think you said it was), so you need to simply connect the two wires to the switch, and it makes no difference to which terminal.

You're not going to have a neutral in that box that goes on the switch; if you did, it would blow the breaker, or fuse.

So, it appears in the pic that there's only two wires to attach to the switch, is this correct?
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Old 04-02-2013, 01:57 AM   #7
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?


Yes it's SP, from my understanding the way the switch works is it allows a small bit of electrify to charge a battery that runs the timer in the switch that's why I was checking. I may just buy a neon tester tomorrow to make sure (can you use a multimeter this way). I just don't want it to catch fire while I'm out of town. Thanks everyone for your time. It means a lot!
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Old 04-02-2013, 02:07 AM   #8
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?


OK, I am thinking that the cable that I indicated with a red circle is probably from the panel, or a j-box, or elsewhere. The black should be the HOT, and the white the neutral.

Use your DMM to measure voltage between the white and black wires (you'll have to unhook the whites that are wrapped with tape). BE VERY CAREFUL, PLEASE.

I don't know what kind of voltmeter you have, but the setting should be on AC voltage, above 120v
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Old 04-02-2013, 02:26 AM   #9
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?


Thanks so much I'll try this first thing in the morning and report back.
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Old 04-03-2013, 05:17 PM   #10
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?


Ok, I went out and bought a neon probe for $15.00 before I start tearing into cables. One line is defiantly in the probe glow bright orange. The other line it flickers (it's actually brighter when I touch the probe to my skin and it lights up). So my assumption is that this is the neutral wire and there is probably some small electrical leak somewhere? Anyway, that being said I installed the switch with these assumptions and it's functioning properly. I left the receptacle open so I can monitor it for a few days and make sure nothing is getting warm etc. Before installing the other 2 switches on the house. Would you guys recommend still testing the wire or do you think this is sufficient testing/precaution.

Would having the smalle leak be dangerous? From what I've read this seems to be fairly common in old houses?

Again, if my wording is off on any of this please let me know as I know very little about electrical components. Thanks so much for your help. This is a great community!
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Old 04-03-2013, 05:18 PM   #11
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?


Also, I don't know if this matters but the cloth wrapped wire was the one that seemed to be hot (glowed very bright).
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Old 04-04-2013, 08:22 AM   #12
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?


Learn the function of a single pole switch..below is basic.

And of course it is not marked but when the switch is on, voltage will also still be measured between 1 & 2.
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?-sp-switch-one-lite.jpg  

Last edited by hammerlane; 04-04-2013 at 11:35 AM.
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Old 04-04-2013, 10:27 PM   #13
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?


http://hostedmedia.reimanpub.com/TFH..._ELETES_07.JPG

Get yourself a non contact voltage tester.

My house is over 100 years old, and I use one of these all the time. The neutral might give a slight reaction, but the hot reaction will be louder
or more obvious depending how it alerts.

Just jet a cheap one, they work fine. Play around with for a bit and you will have no problem identifying the hot conductors.
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Old 04-05-2013, 12:10 AM   #14
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I have 2 black wires, no ground, and a multimeter. Which is the line/hot?


Quote:
Originally Posted by TTW View Post
http://hostedmedia.reimanpub.com/TFH..._ELETES_07.JPG

Get yourself a non contact voltage tester.

My house is over 100 years old, and I use one of these all the time. The neutral might give a slight reaction, but the hot reaction will be louder
or more obvious depending how it alerts.

Just jet a cheap one, they work fine. Play around with for a bit and you will have no problem identifying the hot conductors.
Don't work a damn in a bundle of wires, AND, even if they do show a steady beep, or alert, you can't prove 120v - they're not called idiot lights for nothing.

AND for the reason above, I'd want the most expensive a.k.a. most reliable, NOT the cheapest.

Hammerlane has the right methods.

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