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-   -   four wires inside a cable?! (http://www.diychatroom.com/f18/four-wires-inside-cable-13014/)

joeyboy 11-03-2007 06:57 PM

four wires inside a cable?!
 
I was just up in the attic trying to spice my projector's power cable into a junction box. I've cut these types of wires (seemed to be a regular PC power wire cable) before and have always just seen a white, black, and green.

This cable had a fourth wire inside, a completely loose/unsheathed silver wire. I checked the male head of the original cable to see where it led to, I tore the thing apart slowly and saw that it seemed to go nowhere - that it just ended in the plastic plug right near where the 3 main (power/neutral/ground) wires split to their respective plugs.

What is this extra wire, and more importantly how (please don't say it's impossible!) do I hardwire this to a normal box that's all a 3 wire pattern/setup?

ChristopherSprks 11-03-2007 10:13 PM

Joey....not sure what your problem is because of the terminology you are using. But does this cable you're talking about have a metal jacket, kind of a spiral wrap?
If it does, you have a cable that is called "BX" and that metal jacket is the ground (what you know as the green wire) and that sliver wire is NOT a current carrying conductor. That silver wire is an integral part of the system of that cable and not to be connected to any other wire.
If you want to use that silver wire, use it to hold that red plastic anti-short that goes in of the end of cable in place.

gregzoll 11-03-2007 10:54 PM

If you are cutting the end off of a D plug for a electronic item, the loose wire, is actually for EMI. Personally, I would of placed a outlet right on the ceiling behind the projector, got a 1' cord made for this purpose, along with 1-2' cables for A/V, instead of re-engineering something.

Reason being, is you are doing something that can cause problems later on, and the cords for Electronics are not rated to be directly connected to household wiring with wire nuts.

ktkelly 11-03-2007 11:13 PM

Apparently what you've done is cut the end of of the power cord for the projector?

1. You should not have that cord run into the attic at all as it's not rater for such a usage.

2. You should not even attempt to wire this into a junction box in ANY location.

But forgetting all that "legal" electrical code stuff.....

3. Why on earth would you have a projector plugged into, or worse yet, wired directly into, the electrical power with no way to protect it against a surge?

ChristopherSprks 11-04-2007 12:27 AM

Quote:

Originally Posted by ktkelly (Post 71526)
3. Why on earth would you have a projector plugged into, or worse yet, wired directly into, the electrical power with no way to protect it against a surge?

Maybe he has a whole house surge protector in his breaker panel.

chris75 11-04-2007 07:21 AM

What you did is a violation if you ran that projector cord through a hole in a ceiling, wall, drop ceiling, or floor.... 400.8 NEC, You should have installed a receptacle instead...

tyler101 11-04-2007 10:23 AM

You may be able to find a new cord a www.monoprice.com

ktkelly 11-04-2007 10:29 AM

Quote:

Originally Posted by ChristopherSprks (Post 71536)
Maybe he has a whole house surge protector in his breaker panel.



Which would protect the projector ONLY if a surge came into the structure on the high voltage lines from the service feed.


Sadly, many people are of this same, "I have a whole house surge protector" misunderstanding thinking they have protected electronics when in fact the items are still very much at risk. Low voltage lines (yard lighting, telephone wiring, TV coax, etc.) coming into the structure are often the cause of damage when a nearby lightning strike is the source of a power surge. Additionally, some high voltage lines may be the culprit in these cases (well pump, fountain pump, yard lamp, etc.) where the surge is on the "back" side of the whole house unit.

joeyboy 11-04-2007 10:51 AM

Quote:

Originally Posted by ChristopherSprks (Post 71516)
Joey....not sure what your problem is because of the terminology you are using. But does this cable you're talking about have a metal jacket, kind of a spiral wrap?
If it does, you have a cable that is called "BX" and that metal jacket is the ground (what you know as the green wire) and that sliver wire is NOT a current carrying conductor. That silver wire is an integral part of the system of that cable and not to be connected to any other wire.
If you want to use that silver wire, use it to hold that red plastic anti-short that goes in of the end of cable in place.

there wasn't anything red in the male piece I cut off, the silver wire just ended.

To clarify what I have here, it's a 3 pronged cable. I slice the cable in half, and there's 3 insulated copper wires (white, black, green), one un-insulated silver-stranded wire, and a silver/aluminum insulation that runs the distinace (like the paper stuff in romex).
Quote:

Originally Posted by gregzoll (Post 71521)
If you are cutting the end off of a D plug for a electronic item, the loose wire, is actually for EMI. Personally, I would of placed a outlet right on the ceiling behind the projector, got a 1' cord made for this purpose, along with 1-2' cables for A/V, instead of re-engineering something.

Reason being, is you are doing something that can cause problems later on, and the cords for Electronics are not rated to be directly connected to household wiring with wire nuts.

So basically just get a new cable and instead of having a junction at that box, have a receptacle at it, and then just plug it in? I guess I still don't see why this silver wire cannot be dealt with in any manner besides within a male/female cable - there's just no way around that? (I did use it last night and it was fine :huh: - is it just a problem that may happen down the road or somethign?)

ChristopherSprks 11-04-2007 11:52 AM

Ok Joey .... disregard what I had posted.... has nothing to do with your situation.
My apologies....

joeyboy 11-04-2007 11:58 AM

I'm still confused a bit to be honest - if that fourth wire inside the cable, the unsheathed aluminum (versus the other three, sheathed, copper wires), goes nowhere and is just for interference, how does the absence of the male piece that I cut off affect that? If it doesn't connect anywhere at the end I guess I'm just not seeing why it's not doing its job still... I don't want to fry this thing lol, so if there's no way to make this work I guess I'll have to special order a new cable for it, but I guess I don't see why I can't get something from home depot or whatnot that'll allow me to connect or do something with that extra aluminum wire - didn't assume there'd be some special thing they did with that that I could not duplicate myself.

ChristopherSprks 11-04-2007 12:09 PM

I have very little knowledge with electronics...
but my guess it is an RF drain(to block any electrical interference from the power)....it may not have been connected to anything where you cut the wire but it might be attached to the chassis of the your projector

And take heed to what the others say ....that wire is not suppose to be in the walls or ceiling.

joeyboy 11-04-2007 12:31 PM

so the only way to ceiling mount would be to have an electrical outlet on the ceiling? No way around that, no other cabling I can build myself that'd go to a ceiling fan junction box in the attic, nothing? I guess I've just never seen that before and have seen wires run straight into the attic for powering, but haven't seen too many of these and dunno if the ones I saw were done right I gues :huh:

gregzoll 11-04-2007 12:58 PM

Whenever a projector unit is mounted to a ceiling, you always have a receptacle (preferably a isolated ground, with a Surge protection device down circuit). Also, you have a plate that the A/V cables plug into. Usually these cables are no longer then 1-1.5' to keep from having a huge roll of cable at the ceiling.

Do a search at AVSForum.com for installs to see how others have done it.

joeyboy 11-04-2007 01:49 PM

Quote:

Originally Posted by gregzoll (Post 71595)
Whenever a projector unit is mounted to a ceiling, you always have a receptacle (preferably a isolated ground, with a Surge protection device down circuit). Also, you have a plate that the A/V cables plug into. Usually these cables are no longer then 1-1.5' to keep from having a huge roll of cable at the ceiling.

Do a search at AVSForum.com for installs to see how others have done it.

didn't even think of that lol, already have a username there!!


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