Why did I get zapped?

[Verdeboy]

I replaced a light fixture in the kitchen of an old, funky house. The wires were a mish-mash of old, cloth-insulated Al wires and new, CU wires with plastic insulation. I marked the wires coming out of the ceiling to be sure I would install the new fixture the same way as the old one. There was a red CU wire, which was hot when the switch was turned on. This red wire was wire-nutted to the black wire of the old fixture. There were also a bunch of white wires, some AL and some CU, all wire-nutted together with the white from the old fixture.

At some point in the installation, I got zapped. I determined that one of the white wires was always hot, even though the switch was off. I got smart and turned off the main breaker for the rest of the installation.

My question is: why does the new light work, even though it has two hot wires going to it? I always thought that in order to have a circuit only one wire should be hot.

Keep in mind that the old fixture was wired up this way for years with no problems.

[jimbo]

Given the red wire, you probably have a multiwire circuit with a shared neutral. When you unwrapped the neutrals which were connected together, then YOU became the return path for current coming through anogther load on the other side of the multiwire circuit.

[Chris75]

Given the red wire, you probably have a multiwire circuit with a shared neutral. When you unwrapped the neutrals which were connected together, then YOU became the return path for current coming through anogther load on the other side of the multiwire circuit.

I dont think its a multiwire branch circuit, and I also dont think he broke the neutral splice...

[Speedy Petey]

The red was likely switched, the black of that cable was likely constant hot. A white may have been a switch loop.

How did you determine you had two hots? This is definitely NOT the case since the light works.

Also, WHY did you not turn off the breaker FIRST, and then TEST to make sure it was off????????????????????

I hate to be so blunt, but considering the questions asked, and the description given, I would leave the electrical work to a pro.

Folks always say, it's not rocket science. No, it's not, but you still need a pretty good clue to do even the smallest job. Even changing a light fixture can be a challenge under many circumstances.
This is why my blood boils when I see some handyman advertising "minor electrical".

[Alectrician]

It is impossible to telll where the voltage came from just from your post.


I think it was somewhere between the mish and the mash.

[Verdeboy]

The red was likely switched, the black of that cable was likely constant hot. A white may have been a switch loop.

How did you determine you had two hots? This is definitely NOT the case since the light works.

Also, WHY did you not turn off the breaker FIRST, and then TEST to make sure it was off????????????????????

I hate to be so blunt, but considering the questions asked, and the description given, I would leave the electrical work to a pro.

Folks always say, it's not rocket science. No, it's not, but you still need a pretty good clue to do even the smallest job. Even changing a light fixture can be a challenge under many circumstances.
This is why my blood boils when I see some handyman advertising "minor electrical".

I'm no electrician. But I am a pro, since I charge for my services. I've installed many hundreds of light fixtures, etc.. etc.. but never encountered this before. And, yes, I should not have allowed myself to be zapped. It's only happened a couple of times to me. And, I'm sure it's happened to you, too.

The reason I called the white wire "hot" is because it has juice all the time. When I touch it to the other white wires, it completes a circuit and allows the kitchen outlets to work. The red, as I mentioned, is only hot when the switch is on, and it's not a 3-way switch. I do not see any black wires.

BTW, This is the same guy who uses all that cable tray, since he gets it for free, so doing electrical work for him is always an adventure.

[Speedy Petey]

I'm no electrician. But I am a pro, since I charge for my services.

HA! Nice try at justifying yourself.
That logic is so flawed it's scary.

There is also the chance that you are breaking the law.
Are you insured to do electrical work?
Are you licensed to do electrical work for $$$?
Does the local AHJ know you are doing electrical work for $$$, while being unqualified to do so?


Just getting paid to do something does NOT nearly make you a "pro" at it.

[Cass]

HA! Nice try at justifying yourself.
That logic is so flawed it's scary.

There is also the chance that you are breaking the law.
Are you insured to do electrical work?
Are you licensed to do electrical work for $$$?
Does the local AHJ know you are doing electrical work for $$$, while being unqualified to do so?


Just getting paid to do something does NOT nearly make you a "pro" at it.

The AL and CU should not be just wire nutted together, even if you use "no ox" .

The only way to safely determine if you had 2 circuits would be to turn off each breaker 1 at a time until either both went dead with 1 breaker or you found 2 controlling them. It is most likely 1 circuit like Speedy Petey said..

Occasionally I have found 2 circuits in one box and if they happen to be breaker ed on the same incoming leg you will get 120V on each but 0V across each other. If it was the other incoming leg you would obviously get 240V.

[Bob NH]

I replaced a light fixture in the kitchen of an old, funky house. The wires were a mish-mash of old, cloth-insulated Al wires and new, CU wires with plastic insulation. . . . .
Keep in mind that the old fixture was wired up this way for years with no problems.

It is possible that some wizard wired up a light using a switched neutral. Does the house have Knob & Tube wiring anywhere? In some "funky" installations you can't always count on the white being a grounded conductor.

It is possible to make a light and switch work if you connect the hot to the fixture and connect the other side through the switch to any convenient neutral (maybe not even the neutral associated with that hot conductor). It's often done in automobiles but not legal per the NECode.

You could have all kinds of strange connections if it was once connected as a 3-way circuit where one of the switches has now been abandoned.

[BrianJohn]

Was this a 3-way switch controlled fixture, could be a "hot set" of 3-ways, also called a "Lazy Suzy" and a variety of other names. No longer utilized in the trade.

[Verdeboy]

Just getting paid to do something does NOT nearly make you a "pro" at it.

The lowest paid and poorest performing major league ball player is still considered a professional, by virtue of the fact that he is being paid to perform.

My customers love me. I could give them your phone number, assuming you lived close by, and tell them you are a fully licensed and insured electrician. I could tell them you would work for the same $20/hr that I make. They would still call me.

Why: I removed an 8 ft fluorescent light fixture from their kitchen ceiling. Filled 6 large holes in the hard plaster due to large toggle bolts. Matched the texture perfectly with my patented mesh and vinyl spackle technique.

Installed their new light fixture.

Fixed their leaky drain under the sink.

Secured their loose gutters.

All for less than any one of these things would have cost if they hired a "pro" like you.

Thanks to the rest of you who gave advice in a non-patronizing and non-condescending way.

[Speedy Petey]

Well, considering you took a customer's light fixture down and had to come on here to ask how to hook it back up because you did not even know how to decipher the wiring, I worry for your customers.
You might want to consider that insurance I mentioned.

$20 an hour?? You must be proud.

[Lakee911]

I would stick to those things that you know like spackling and fixing gutters and avoid the electrical work. If you can not decipher the wiring and you are electrocuting yourself you're likely to end up dead, not to mention be a liability for the homeowner. Did you use a proper and listed connector for the Al and Cu wiring? They can't just be nutted together.

I don't think anyone is intending to be rude, but this can be dangerous stuff in the wrong hands. If we overlooked the fact that you're unqualified and practicing dangerous techniques (like leaving the CB on and not testing wires for voltage with something other than your body) then this isn't setting a good example to other readers of this forum. There are real professionals who go to school or enter the field as an apprentice and are properly trained for this kind of work.

Jason

PS. By the way, drywall compound (vinyl or otherwise) isn't the best repair method for plaster holes. Many do it, but you're likely to end up with cracks between the two mediums because they expand and contract at different rates. Not that its much of a big deal on the ceiling, but the dry wall compound isn't as durable as the plaster. It's much too soft. Hey, what's your patent number?

[Alectrician]

Verde, you have to understand and visualize a complete circuit.

The simple version is that the power comes in on the black and goes back on the white. If it is seperated at any point the electrons will not flow.

If the hot circuit to the kitchen outlets is hooked up and the referigerator is plugged in, the current is flowing in on the hot, thru the refer and headed back on the neutral.

When you separate the neutral and interupt the path, the juice is still there trying to get back to "ground" and will take whatever path is available, including thru you.

Also, for future reference, you need to be very careful when separating energized neutrals. There are cases that, by simply separating the neutrals, you can cause 240V to go to the 120V outlets and do some major damage.


That said, I think, except for a few exceptions, only electricians should be doing electrical work.

[frenchie]

I'm no electrician. But I am a pro, since I charge for my services.

You & I have been down this road before, and I'm not looking for a re-run, or to pile on with the electricians - but I have to argue with your definition of "pro". Being paid to do it doesn't make you necessarily a "pro", it can also make you a "hack". "Pro" implies a certain level of know-how, training, etc.

So, while I don't care that you're unlicensed to do this work, in a state that requires it - I am going to tell you again, that I think you don't take the hazards of electricity seriously enough.

You got zapped because you take chances. You could've gotten killed, instead of just "zapped". And you could've started a fire (at the time, or much later because of something you did at the time).

Seriously, Eric: lose the attitude, understand how much there is to learn compared to what you know, and start learning it. Get some books, read them. Download the NEC, and study it. Lurk around the pro sparky websites, read their discussions and arguments, learn the hows & whys & therefores...

Stop gambling with your & your customers' lives. The next time you might not be so lucky.

Oh - and buy yourself one of these, in the meantime: