finding a live wire?

I am going to add a pair of recessed spotlights in my living room ceiling to illuminate a picture over a fireplace. The attic space over the living room is easily accessible. My idea is to tap into an existing wire in the attic for power to the spots. There are about a gazillion wires up there . . . most tied into a switch somewhere in the house. Any suggestions as to how I identify a live wire without actually cutting into it?
TIA
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Try a circuit breaker finder. Plug one end into an outlet near where you need the power, then wave the sensor over the various wires in the attic.
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Finding a wire is only part of the problem. You'll need to know what circuit it's on (certain things, like major appliances, must be on a dedicated circuit). And once you find a good candidate wire, you need to splice into it.
This is more tricky than it might seem. Splices MUST be done in an accessible junction box. This rules out just wire-nutting on a new wire to the old one. And you'll need about 10-12" of slack in the existing wire to make the new connections and add the box. Unless the original electrician was VERY messy, you probably don't have this. One option is to use two boxes, and a new piece of wire between them. You MUST make sure the new wire is the same gauge (or larger) than the old. Remember smaller numbers larger gauge.
-Tim
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Tim Fischer wrote:

And then he will need to figure out how to turn it on and off.
--
Joseph Meehan

Dia duit
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snipped-for-privacy@xs4a11.nl wrote:

I believe they detect the magnetic field from current drawn the 'sender' unit. Nice method if the 'sender' is downstream from the attic wires.
bud--
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What do you mean by "live"?
Why don't you just assume that they are all "live", since unless you have taken the steps to shut off a particular circuit (and do it correctly), pretty much any wire up there could go "live" at any moment (for whatever definition of "live" you want to give).
I don't see what you are trying to do here. If you happened to find one wire that had current passing through it at any particular moment, that still doesn't tell you if it would be a good one to tap into (maybe its on a light switch, or a dedicated appliance circuit, or 240V, or a timer, or a thermostat, or who knows what else). And even if it didn't have current passing through it at the moment (and some line testers won't tell you unless there is current), it might still be at 120V or 240V, and you don't want to touch that either.
The only "dead" circuit in your house should be the ones that you yourself shut off (and made sure no one will turn back on).
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There are non contact electrical testers. Go to www.mcmaster.com and see a couple on page 691. Any electrical supply house will have them. About $15.
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I'm no electrician but the key element is finding the right circuit and turning it off.
Sometimes its easier (and safer) to start at a receptacle in the area near where you want the switch.
Find the breaker that turns it off. See how many other receptacles /lights are on it.
If not more than the limit allowed in your area you could feed a power wire up from the receptacle to a switch and up from the switch to the attic and your pot lights.
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But isn't this now against code- lighting fixtures and receps on same circuit? I think you're going to have to find a lighting circuit that is not already fully loaded- have to check with building dept. or local electrician for rules on that- and make sure you won't be overloading it with addition of new fixtures. Otherwise, run new circuit, again if space/ load available. Most likely you can tap into existing circuit, as Tim described above, though I guess I've seen some sloppier elec work with plenty of slack in cables(sounds like this might be the case in your situation) meaning you'd only need one junction box. Then, as Joseph says, you'll need a switch, meaning you'll have to run cable from junction box either through switch to fixtures or through fixtures to switch, whichever seems most convenient.
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I know of no rule against this, except possibly on multi-bathroom circuts. It would be a really odd rule, since a switched receptacle can BE your lighting circut.
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Sorry, apparently I muddled what I heard. Apparently it is fairly common practice, though, so tripping a breaker doesn't put you in the dark. Wouldn't apply in this case, though.
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Huh? Can't put ligting and receptacles on the same circuit? Really? Never heard of that one. Can anyone back this up, or explain it?
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Hold on there, Bubba! Your idea is a last resort. (More work)
You need power and a switch leg...
Where are you going to switch the spots?
Perhaps you could put the switch box near a receptacle and pull the power from there.
Is there a switch box on a wall at the living room entrance? Maybe you can get power from that location, maybe not.
Do you have a ceiling fixture in the room? Maybe you can get power from there.
How about a light, receptacle or fan in the attic? Check there...
Any junction boxes at all in the attic? Look there.

If you must... Buy a cheap detector that lights up when you touch it to the outside of the romex. 14/2
I just picked one up for under $5.
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