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OT wiring an AC lamp socket

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Dave H (MI)

Well-known Member
I am rewiring a wall lamp in the farmhouse that has old cloth wires that are not in the greatest shape AND they are all white. Here is what I think I need to do, tell me right or wrong. When I wire the light socket, the black wire is hot and needs to go to the connector that contacts the center of the light bulb. The white wire is neutral and goes to the connector that contacts the metal threaded socket. Is that correct?

One more question, the guy that wired the house back in the 1930's received a hog for his labors. Can I use my multi meter to verify which are the hot and neutral wires? The old wires in the box are all black and were not connected when I took the fixture off the wall.
 
Being the wiring is that old, good bet that is only a 2 wire system with no ground.

To determine which is the "hot" wire, you'll need to ground one lead of the volt meter to something metal that is in contact with the ground, like a water pipe, metal siding, etc. Then touch the other lead to each wire. The one showing a reading, 110-120vac will be the hot.

Be careful disturbing that old insulation, trust nothing!
 
Just keep in mind......those old systems can feed back. As stated with a super good ground,take some readings around your house. The feed back can be a few volts but should not be much more. The voltage actualy passes through other equipment and feeds the ground side. Sounds like it is time to rewire that house and you want 14/2 for all of your outlets. Gives you a white,black, and a full size ground wire. Your lamp is correct but you need a polarized plug or it will be mute. That plug with one larger prong. Keep asking questions. All of us will try to help. Also you want to go to breakers. Fuses are not approved by many insurance companys! Hope I helped.
 
OK, I will. So I believe you are correct, but not sure how many wires are actually in that box. This is a plaster and lathe deal with a lot of modifications over the years. I know there are none of the usual bare copper ground wires. I will look down in the cellar and see if the wires come out down there. Maybe I can trace back to the source and see what the configuration is. Kinda doubt it though.
 
Yes you did. I would have been pretty confused if I picked up that feedback and didn't have an explanation. So this house, to make a long story short, was built on the foundation of a 1860's era house that burned down in 1931. It was rewired by the last owner's FIL who was an electrician...supposedly. A brand new breaker box with new breakers was installed...none of them marked. Off the top of my head I cannot tell you how far they went with the rewire because I did not care. The only important thing was to buy the property because it is right in the center of my farm. I can tell you that the wires in the walls are original so I bet if I look down cellar I will see new wires going to junction boxes with old wire coming out. I will give the meter a try. I can ground to the bathroom plumbing right next to the fixture. Thanks!
 
Make sure you know which wire is hot. When I was rewiring our old house, I bout got knocked on my tail because I started to unhook the hot wire on a light, with the switch turned off. Come to find out they had run the ground wire through the switch.
 
Dave,

I'm not an electrician but I've done a whole lot of wiring for myself and my family members over the years. I've always pulled permits and had the work inspected on any new/sizable work that I've done. I think I have a pretty fair understanding of household wiring.

Having said that, I would make just one more observation about your trying to determine which wires are hot. IF the plumbing in the house is absolutely all metal, you can probably pick up a ground from the plumbing. If, however, at any time during the past 100 years someone has replaced any of the water lines or sewer lines with PVC pipe, there is a good chance that the plumbing is no longer at ground potential. The good news is that neither of the wires that you are trying to determine is hot will show primary voltage on your meter if the reference point that you are working with is not at ground potential. But don't just measure one wire, see that there is no voltage on it, and assume that is the neutral wire. Check both of the wires to insure that one is at primary voltage and the other is at zero potential before you make any decision about which wire is "hot".

Good luck with your problem determination.

Tom in TN
 
Call an electrician to check all the wiring. I had an old house with the cloth wrapped wiring. The wire insulation was so rotted that it just crumbled everywhere it was exposed to the air. The house almost burned down one time. Please have it checked by a professional .
 

Good for you Dave, being self reliant and doing it yourself. But it really is not OK to do it until Jan. 20th.
 
I think the big box stores (Menards, Lowes, Home Depot etc.) have a device where you just touch a wire no metal to metal contact, and it will indicate hot or no. Pete
 
I would not recommend rewiring with 14 gauge wire on any of your outlets. It is much better to use the larger 12 wire as it will have much less resistance and can carry more amps. In my limited experience most house type wiring comes in gauges such as 12-2 with ground so there is really 3 wires that you actually use. If you do not know how to check for the hot wire I would get some expert help.
My old house, built in the 1860, had that old wire and I replaced it all and I also upgraded to a 200 amp service. I run several outbuildings off that system now with no problems. Have a happy and sfe holiday season.

Also I believe that on lighting outlets it is common o break the ground or neutral wire at the switch. In that case I doubt that the wire at your light is hot but be sure.
 
On a house that old watch out for switched neutrals where everything is backwards. Whatever color the fixture leads neutral on a socket is screw shell ,that is code.
 
I like the idea of 14 gauge wire over 12 gauge but with a 15 amp breaker That will handle any normal household loads and you just put more circuts in and have things seperated more. That 15 amp breaker is more likely to trip if there is a problem that will not trip a 20 amp breaker for the 12 wire so more likely to make a fire. If you have one kitchen apliance that is over half the 15 amp on that circut put in an extra circut. Now if you want to put in a 15 amp breaker on 12 wire that would be good, just harder to get the wire to work and more money than seperating things and keeping the load small.
 
Yes Pete. Also known as a proximity tester. kline makes one for around 15 bucks. I use one on my sons house, to find the hot wire on "knob and tube" wiring, where both sheaths are black. Just rub it along side the wire, and the hot "beeps"
 
Be careful of any circuits that have a 3 way on them like the stairway. The old way of wiring them would use 2 separate hot wires and neutrals. If the 2 hots are not on the same phase then you feed 240 volts to the bulb, very bright but short lifespan lol.
 
(quoted from post at 23:01:52 12/21/16) Be careful of any circuits that have a 3 way on them like the stairway. The old way of wiring them would use 2 separate hot wires and neutrals. If the 2 hots are not on the same phase then you feed 240 volts to the bulb, very bright but short lifespan lol.
Click to expand...
rawing please?
 
Why would you not use 14-2 with ground where it is acceptable. Do you know how low the load requirements are on the non dedicated circuits? 12-2 wg cost a lot more money and is harder to work inside the boxes. Also requires larger cubic inch boxes to stay within the required box size based on the number of conductors in the box. I have wired hundreds of houses and have never been called back to one because of problems with a 15 amp circuit being too small. It is all in how you divide your circuit wiring. It gets real expensive when you start wiring 3 way switches with 12/3 with ground wire.
 
Easy way is one of those voltage sticks, when held close to hot, it will beep or glow. Lifesavers, can be used day in and day out.
 
Here is a diagram, and no I didn't go to art
school lol. As shown, the switches will
either feed the light a hot and a neutral, 2
hots, or two neutrals. The safety issue is
that in one position the screw shell of the
light fixture is hot instead of the tab. If
the circuits are on 2 different phases then
the 2 hots will feed it 240 volt and burn
out the bulb. The 2 neutrals will play he11
with arc fault breakers. This is a very
common style of wiring in my area for houses
wired with knob and tube, usually 1920's
vintage through the 40's. Hope it helps
a245981.jpg
 
At the risk of being called a Billy Bob, shot down in flames, swore at etc I will say that the reality is that since the branch circuits in your house are wired with only two wires that it does not meet current codes no matter what you do. Thus saying that wiring the fixture one way or the other meets or doesn't meet code is bunk. Wire anyway you wish it isnt going to meet current residential codes. As for which way it is safe, meaning absolutely safe vs dangerous it makes absolutely no difference because "safe" is not a definitive term, it is relative term. That is why codes keep changing, Ohms law hasnt changed, just the public view of "safe" thus we now have 3 wire 110 4 wire 220 etc. A question for those who would argue my point is this; If a lamp requires the leg wire to the center and the neutral wire to to go to the metal threads to be safe vs dangerouse please tell me why can we go to any store, purchase a desk lamp with a two wire cord that has a nice little UL laboratories listed tag on it yet it can be plugged in either way which cases not only the lamp but the switch being reversed?? UL labs must be out to kill me?? LOL

All that being said, IF you can determine which one of those wires is indeed the one that has 110V potential above ground then by all means attach that wire to the center contact for the bulb because it is indeed the prim and proper and safest way to do it. If you cannot determine which is which then attach the wires, put the fixture back in the wall and quit worrying about it. One way being safer than the other is cutting some pretty fine hairs that I personally dont cut.
 
that is so bad, Greg, that I had forgotten about it. :(
Some here used to use it to have power AND 3way switched light at outbuilding with only 3 wires. Light off and everything HOT! Surprise, surprise! :twisted:
 
Lol. I may have phrased it poorly too. The
guy I apprenticed under called I think a hot
3 way but there are probably a dozen
different names for it.
 
I had to deal with a similar circuit on Monday. I am very skittish around anything electrical so when there was no obvious problem I got an electrician in. It turns out that the upper and lower switches were powered off two different breakers. Without a pro who knew how to tell by his multimeter what was going on I would still be in the dark.Literally. The electricians dispatcher sent one of his guys from another job, he checked things over, changed a bad switch and was gone in less than an hour. I got invoiced for the minimum charge($90) and 5 for the switch. With taxes the total was $108 Canadian. I think it was cheap considering what my peace of mind is worth and my insurer can't say I was monkeying with the wires.
 
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