I need to replace the socket and wires for a halogen sconce from the 1970s.
I couldn’t find an exact match. On the sconce it says not to use a bulb over 100W; its socket is marked 500W and has silver-colored wire. The only replacement I could find is marked 150W and has copper wire. I assume that 100W bulbs are safe.
Instructions say to match the wires according to color, but the wires coming out of the wall and the wires in the old socket are all brown. How do I determine which is white and which is black?
Janet
Replies
Scrape off the brown burned stuff so you can see which is black and which is white. N0, really. The neutral (white) brown should have raised ribs along it's length. Failing that, check continuity from the threaded part of the socket to the browns - whites goes to the socket.
Forrest - not an electrimetyrician
Neither wire connects to a threaded section. It's a double-contact, bayonet-style socket like this one:
http://www.flickr.com/photos/dwread/4006648702/Janet
Determine if the socket is polarized. (Check for one of the keyhole slots being deeper than the other, so that the lamp can only be inserted one way.) If polarized, obviously hook it up the same way. If not polarized then it presumably makes no difference which wire is connected to which.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
You're right! Thank you.What happens if the white and black wires are not matched up?Janet
In the case of the type of socket you have, it probably doesn't make any difference which wire goes where. With a traditional "Edison" base the intent is that the center contact at the bottom be the "hot" and the screw base be neutral. This reduces the shock hazard if someone changes lamps with the power on. On some other socket types there is a similar preference based on which contact might be more easily touched accidentally.A few types of lamps need a specific side to be grounded for reasons having to do with how electrical charges are distributed in the lamp, but tungsten-halogen lamps don't fall into that category.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
Most probably the answer is that it does not make any difference in your case, with the double bayonet base, which supply wire which is which.
The only 100% safe way I know is to measure / check for continuity between the two wires with the breaker turned off.
After the breaker is turned off, you would touch the two probes from your continuity meter to one wire and and the grounded box (or bare ground wire). You should find continuity between one wire and the box or ground wire. The wire which shows continuity is the "neutral" or white. The remaining wire which does not show continuity with ground is the "hot" or black.
Although many here would not admit it, most would probably check for voltage between the two "brown" wires and ground source (box or bare wire) with the circuit hot - the wire which is showing voltage is the hot or black wire. This could also be accomplished with a non-contact voltage detector.
Whichever way you determine supply wire identity; remark the wires with appropriate colored tapes to avoid any future confusion.
You found ribs on the wires in the wall box? Unusual.......
Or, was it that you found ribs on the wires contained in the fixture? More normal.
Jim
Never underestimate the value of a sharp pencil or good light.
Edited 10/15/2009 2:02 pm ET by JTC1
Is this "lamp"? That is something with cord and plugs into the a receptacle and hangs on the wall like a picture.Or is it light fixture that has screws to mount into a electrical box.The reason that I ask is that a light fixture will not have wiring with a rib on it. While, if it is old wiring the wiring might have turned brown with age and heat. However, if you have lamp cord inside an electrical box then that is a no-no and can indicate all kinds of very dangerous situations.Note, that is a few case "lamp cord" is used for internal wiring in a fixture. One common example is hanging lights where the cord that is intwined with the chain. Otherwise, AFAIK, all internal fixture wiring is done with discrete wires..
William the Geezer, the sequel to Billy the Kid - Shoe
< done with discrete wires >
Love that term. Here at work, in LED land, I have a sign in my office that says,
Discreet LED seeks same
Forrest
It doesn't have a plug. The wires are hidden in the wall.The wire was not ribbed. It turned out that none of the brown wires were part of the house wiring. What I thought were wall wires were actually bridges between the wall wires and the lamp wires (which were too short). I yanked on them and brought out the white and black. The fact that the wires are silver-colored...does that mean they are aluminum?--and I should go through the fixtures and replace them?Janet
Edited 10/15/2009 5:53 pm by jyang949
Which wiring is silver? If the house wiring is silver that would indeed suggest aluminum wire, but if the wire from the fixture is silver it's probably just "tinned" wire -- wire that's been coated with solder.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
The house wire is thick copper. The fixture wire is several strands of silver-colored wire. I guess it's not aluminum, then. Thanks!Janet
The light fixture attaches to a bracket that in turn is attached to the wall. There is a bare copper wire attached to a green screw on the bracket, but the other end of the wire was not connected to anything when I took the fixture down. Where is it suppose to connect?Janet
It will connect to a bare or green wire in the house wiring. That is the ground wireHowever, if this is an older house (pre 60's or so) where the wiring does not have a ground wire then you won't have one in the box.No real concern for a light fixture..
William the Geezer, the sequel to Billy the Kid - Shoe
Of course, we haven't clearly established (to my recollection) that the wiring isn't BX, in which case the metal shell of the BX cable serves as the grounding conductor.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
Just for the heck of it, I used an inexpensive circuit tester on the wires. It lit up as expected when the two probes touched the wires.
What surprised me was that it lit up when only one probe touched the black wire. It was very faint compared to the first test, but should it have lit up at all? I thought a circuit tester needed, well, a complete circuit in order to light.
Is this a problem?
Janet
Not at all unusual for a neon tester. "Phantom voltage" due to capacitance.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
>>....if you have lamp cord inside an electrical box then that is a no-no and can indicate....<<
That's where I was headed also.....not to say I have not seen it.....more than once.
JimNever underestimate the value of a sharp pencil or good light.
Forrest, how did you know the wires had burned--just because they were brown? Janet
Just a lucky guess - and I've seen some brown and crispy wiring in old light fixtures.
So - I'm guessing it's all better now?
Forrest
Yes, everything works fine, thank you. I was wondering if this indicated a dangerous situation, and changed the direction of the lampshade so it points up. Janet
One of the things that changed, I believe in the '80s, was that manufacturers were required to use luminaire wiring that was rated at a higher working temperature - I think it went from 90 to 105 degrees C.
Plus, halogens are hotter than pure incandescents just due to their design.
Glad it all works now.
Forrest
As McDesign says, match up the wires based on which part of the socket they feed.