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if I know how to take the live wire off then my job is easier.

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I whole-heartily agree with Niall C and GregMac. Working with a live circuit can be VERY dangerous. DON'T DO IT! – Mike B Dec 4 '10 at 19:02
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Just to clarify your question, do you mean: I have a two-way switch and I'd like to run something off the wiring? Or do you mean: How do I work on a switch without turning the power off? – Sean Reifschneider Dec 6 '10 at 6:47

4 Answers

up vote 9 down vote

Never, ever, work on live electrical wires.

Turn the power off at the breaker/fuse. You should have a voltage detector to verify the power really is off, like one of these:

alt text

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These devices are really nice. Very easy to use and a quick result. – Jay Bazuzi Dec 4 '10 at 19:13
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Cheap too. You should be able to find them at the local hardware store for under $20. – KeithB Dec 5 '10 at 15:04
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always test this type of device on a known hot source to confirm it is working and battery is good. Dead battery makes dead men. – shirlock homes Dec 5 '10 at 20:31
@shirlock homes: Good point, and I always do that as well. If it doesn't beep, I'm skeptical until I actually hear it beep by testing on another circuit. Then I go back and confirm it really isn't beeping on the wire I'm about to touch. – gregmac Dec 7 '10 at 16:27
Unfortunately these devices will frequently beep even when the circuit is not live, because an unpowered circuit can pick up a small stray voltage from running next to an adjacent powered circuit. – Lev Bishop Feb 16 '11 at 1:45
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up vote 6 down vote

First of all, if you don't know exactly what you are doing , working on live wires is extremely dangerous. On a three way switch circuit, (light or devise controlled by two switches) the hot wires change depending on the position of the switches. Only one switch has the hot feed on the off colored screw, the load hot on the other switch off colored screw, but this hot feed is always present on one of the idler conductors, and changes with each change of state of a switch. Do your self a favor and turn off the breaker and confirm power is off.

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up vote 5 down vote

Unless you know exactly how the circuit is wired, you should assume that both wires to the switch are live. The only safe way to work on anything electrical is to turn the circuit off at the service panel, and then check that there really is no power at the fixture before starting work.

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up vote 4 down vote

As others have pointed out, you're obviously much safer if you ensure there's no power to the wires you're working with.

  1. Use a tester to confirm that there is power in the circuit, that your testing tool works, and that you know how to use it correctly.
  2. Tell people in the area what you're doing, so they don't flip the breaker back on.
  3. Flip the breaker off.
  4. Tag the breaker, so no one else turns it one while you're working.
  5. Close the breaker panel.
  6. Use the tester to confirm the power to the circuit really is off.

Risk goes up if you're working with a 240V circuit (anything in the UK; clothes dryers, ranges, heaters in the US) or if you're well grounded (standing in a puddle on a concrete floor; holding a cold water pipe).

That said, many electricians work with live wires, especially when it's only 120V. I've done it by accident, when one of my kids decided to "be like daddy" and turned on the circuit I was working on. It didn't really hurt, it was just annoying. As a shortcut to turning off the breaker, some will short across the lines with pliers or a screwdriver, which flips the breaker. I'm not advising either practice, just as I don't advise driving without a seatbelt or using a chainsaw naked.

If you want to cut a live wire, try you can use a pair of insulated pliers. Every electrician (amateur or pro) should have a good pair of lineman's pliers. They can be used to strip wires and to tighten wire nuts, too. Lineman's Pliers

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I have a bunch of expensive Klien linesman pliers rendered useless after cutting through hot wires and melting big ole circles in the cutting blades. If you insist on working hot wires, keep one hand in your pocket and stay off metal ladders and concrete floors! – shirlock homes Dec 5 '10 at 20:29
I just had an electrician here working on a light fixture. To test it, he stuck his finger in the socket. Didn't flinch. – Jay Bazuzi Jan 11 '11 at 23:03
Ok so yes, it can be a pain in the ass to always use your tester and to figure out how to turn off the circuit. Is what you're doing really so time-critical that it's worth risking getting seriously and/or permanently injured or even killed? The worst thing is that an electrician can probably go his whole life testing light sockets that way.. but the one time he accidentally touches something grounded with another body part, he's toast. Not worth it for an hourly wage in my opinion. I can't imagine it's even a good thrill, like other activities with similar risks.. go skydiving or something :) – gregmac Feb 17 '11 at 17:27

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