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?
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.
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).
I'm no electrician but the key element is finding the right circuit
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.
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.
Hold on there, Bubba!
Your idea is a last resort.
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?
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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