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Old wiring (K&T) - which one is hot, and how can I be sure there is no current?

Old wiring (K&T) - which one is hot, and how can I be sure there is no current?

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  #1  
Old 09-19-13, 06:45 PM
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Old wiring (K&T) - which one is hot, and how can I be sure there is no current?

Hi there,
So I recently moved into an old Brooklyn brownstone built in 1905. Naturally, it has the old knob & tube wiring in everything. I wanted to replace a pendant light with another one so I shut off the power from the circuit breaker and unscrewed the old fixture/canopy.

But three confusing things happened.

1. A guy at my local hardware store convinced me to buy a non-contact voltage tester (he said it was better than the multimeters I am familiar with and used to own). Honestly, so far, I find the thing inconsistent and confusing and leaves me feeling unsure.
Even when the circuit breaker is completely off for the entire apartment, and the light not turning on (as well as other lights on the same switch), and no outlets working, I still like to test for voltage out of a safety paranoia. And when I went to test the old light fixture in question, the non-contact voltage tester was lighting up like crazy! On both hot and neutral wires, all in and around the socket, etc! All this even though the bulb won't turn on-- and I've since turned the power back on and the bulb lights up, so it's not a dead bulb in question. I feel almost certain there couldn't have been any live current, but if the voltage tester is telling me there is how can I be so sure? Should I just get a voltage meter / multimeter to be more certain? My non-contact tester was $12, so maybe it's just cheap & inaccurate? (this one: Amazon.com: Sperry VD6504 Adjustable Volt Sensor Non-Contact Voltage Detector, 12-1000 VAC: Home Improvement)
One thing worth noting is that my breaker only controls the power for my apartment and there are other units in this brownstone. Is it possible that my non-contact tester is picking up on nearby wiring in the ceiling designated for other apartments? The thing is, the tester only lights up when I touch it directly to the wires/fixture, but not even centimeters away, so I wouldn't think that to be the cause...

2. With this old K&T wiring, how can I tell which one is hot and which one is neutral? The old cloth insulation is the same color (both black). Is it a matter of testing when the power is on, contacts on hot+metal = 120v, neutral+metal = 0-1v? I remember this much from basic wiring but I want to be sure before going in, unless there is a better way to tell...

3. Lastly, there is no proper junction box. It's just some sort of ceramic thing wedged into the ceiling and some black box inside that but it doesn't look like any junction box I've ever seen. Not sure how I can mount my pendant light. The good thing is, it's basically a bare-bulb design that is extremely light. Could I just mount it to the ceiling with anchors if it comes down to it?

Thanks in advance!
 
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  #2  
Old 09-19-13, 07:09 PM
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If you are not the owner and or the only resident due to liability and local ordnace. You should hire an electrician. NYC is very strict on this.

1. A guy at my local hardware store convinced me to buy a non-contact voltage tester (he said it was better than the multimeters I am familiar with and used to own). Honestly, so far, I find the thing inconsistent and confusing and leaves me feeling unsure.
Here we recommend a cheap analog multimeter. There are very limited uses for a non contact tester but not enough to make them a must buy. A analog multimeter is a must buy.

With this old K&T wiring, how can I tell which one is hot and which one is neutral?
Using a multimeter you measure to a known ground. Neutral will show about ~0 volts, "hot" ~120v. You can use a grounded extension cord plugged into a know properly grounded receptacle as your reference or lacking that run a wire to a metal water pipe.

You need to install a proper box.
 
  #3  
Old 09-19-13, 07:16 PM
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With this old K&T wiring, how can I tell which one is hot and which one is neutral?
There is actually a much easier way to test for this without using a multimeter, but since this is an apartment you really have no reason to know how. Talk to your landlord, this project is his responsibility IF he will allow it at all.
 
  #4  
Old 09-19-13, 07:25 PM
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That's the way I learned how to test when the wires look the same. Test between the wire & metal. Was the building converted into a 6 apartment dwelling? They were usually 3, one apartment per floor. If they converted it, who knows what they did with that wiring? Some gas boxes for old style kerosene lamps were converted to junction boxes for electric. You might be seeing that. Try to find a joist to hang the light. What kind of lath is there?

Edit: Are you in Park Slope?
 
  #5  
Old 09-19-13, 07:29 PM
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Joe's way works but it uses a device I just don't trust. That though is personal opinion and moot here because the poster shouldn't touch the wiring.
 
  #6  
Old 09-19-13, 07:31 PM
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How do you know that he didn't buy the building? My cousin owned one there.
 
  #7  
Old 09-19-13, 07:49 PM
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Joe's way works but it uses a device I just don't trust. That though is personal opinion and moot here because the poster shouldn't touch the wiring.
What's wrong ray, you don't like touching hot wires?

I agree, the OP shouldn't be doing anything with the wiring in his apartment.
 
  #8  
Old 09-19-13, 09:23 PM
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How do you know that he didn't buy the building?
The property owner has access to the main distribution panel, not just one breaker. Also, he or she, typically, does not live in an apartment.
 
  #9  
Old 09-19-13, 09:54 PM
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How do you know that he didn't buy the building?
The property owner has access to the main distribution panel, not just one breaker. Also, he or she, typically, does not live in an apartment.
Well actually, in NYC, it is quite normal to purchase an apartment (e.g., one unit, or one floor), as part of one larger building with other tenants who also purchased or rent their apartment. Co-ops and that sort of thing. Very few people I know own entire buildings.

Pulpo -- I am close to Park Slope; Clinton Hill/Ft. Greene to be exact. Similar setup, 4 floors, 3 apts for floor.

Anyway, I have never really lived in a place where I had not changed out lighting fixtures and changed light switches to have dimmers. It's pretty standard wiring and I've done it dozens and dozens of times. Never had to get approval from a landlord and I think that's stretching it a bit for a basic light fixture change. Thing is, I know what goes where, just a little confused by the way a non-contact voltage tester would go crazy and the lack of proper labelling from the old days. Will have to try the analog multimeter which I'm used to anyhow and then I will know for sure, and try to test for the hot. Thanks guys!
 
  #10  
Old 09-19-13, 10:01 PM
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Also, Pulpo, I don't know enough about lath & plaster & ceilings to know the exact material if that is what you're asking...
 
  #11  
Old 09-19-13, 10:04 PM
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Welcome to the forums!

I recently moved into an old Brooklyn brownstone built in 1905. Naturally, it has the old knob & tube wiring in everything. I wanted to replace a pendant light with another one so I shut off the power from the circuit breaker and unscrewed the old fixture/canopy.

But three confusing things happened.

1. A guy at my local hardware store convinced me to buy a non-contact voltage tester (he said it was better than the multimeters I am familiar with and used to own). Honestly, so far, I find the thing inconsistent and confusing and leaves me feeling unsure.
Even when the circuit breaker is completely off for the entire apartment, and the light not turning on (as well as other lights on the same switch), and no outlets working, I still like to test for voltage out of a safety paranoia. And when I went to test the old light fixture in question, the non-contact voltage tester was lighting up like crazy!
Non-contact testers have their uses, One is indicating the presence of ungrounded power. The other is.. oh, yeah, indicating the presence of ungrounded power.

That said, turning the breaker off should have killed the power to the fixture. It didn't, if your squawk stick is working properly. If you killed the power then you killed the power. Did you test your tester before using it?

One thing worth noting is that my breaker only controls the power for my apartment and there are other units in this brownstone. Is it possible that my non-contact tester is picking up on nearby wiring in the ceiling designated for other apartments? The thing is, the tester only lights up when I touch it directly to the wires/fixture, but not even centimeters away, so I wouldn't think that to be the cause...
Actually, that may be an indication that it's picking up induced voltage.

2. With this old K&T wiring, how can I tell which one is hot and which one is neutral? The old cloth insulation is the same color (both black). Is it a matter of testing when the power is on, contacts on hot+metal = 120v, neutral+metal = 0-1v?
Yes, provided the metal is connected to ground. Another way is to plug a 3-conductor extension cord into a grounded receptacle and use the ground slot in the female as one of your probe contact points.

3. Lastly, there is no proper junction box. It's just some sort of ceramic thing wedged into the ceiling and some black box inside that but it doesn't look like any junction box I've ever seen.
That box may be acceptable. K&T wiring in good condit6ion is still allowed to be used, and many of the fittings used with it are too. That said, the splices that connect your fixture wires to the house wiring must be in an approved enclosure. The existing box plus a canopy may meet that requirement.

Not sure how I can mount my pendant light. The good thing is, it's basically a bare-bulb design that is extremely light. Could I just mount it to the ceiling with anchors if it comes down to it?
You could, if you also mounted a box to enclose the splices. Do you see the end of a pipe in the center of the existing box? If the original gas pipe is still there, and if your new fixture has a fitting for all-thread at the top, you can use a hickey to mount it.
 
  #12  
Old 09-19-13, 10:52 PM
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The owner of the property, even if it's a condo association, has access to the main distribution panel. My friends who live in apartments in Brooklyn have access to the overcurrent protection devices that protect all of the wiring in their unit.

I suspect you do too, and that your non-contact voltage tester was reacting to induced voltage. Go with the analog meter.
 
  #13  
Old 09-20-13, 02:07 AM
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jwing, If you see thin strips of wood behind the plaster about 3/8" think, that's wood lath. It can hold a small light fixture. If you see sheet rock, that apartment was added at a later date. That brings up questions about billing but that's another story.

BrooklynPix.com - Brooklyn New York City NYC Photos Pictures Books -- Most Complete Archive of Old Brooklyn Photographs Click on any neighborhood.
 
  #14  
Old 09-20-13, 07:40 AM
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Well actually, in NYC, it is quite normal to purchase an apartment (e.g., one unit, or one floor), as part of one larger building with other tenants who also purchased or rent their apartment. Co-ops and that sort of thing. Very few people I know own entire buildings.
So, you never said, do you rent or own the apartment?
 
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