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Question How do I safely replace a bad light switch? (Posted by: Anonymous )

James P. Oskolkoff Answered by: James P. Oskolkoff, an
expert in the About Electrical Safety category
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Back about 20 years ago when I was a wee electrician's apprentice up in Alaska, the first journeyman electrician I worked for pulled me aside and said with a very stern face behind his full gray beard; "James, you see all these electrical devices, light switches, receptacles, light fixtures and such? Well, they all run on smoke, if you let the smoke out, they won't work no more! Don't let the smoke out!

Funny, but okay, not really... I never have forgotten that colorful lesson and suppose you could apply the same analogy to yourself. When you're working on electrical systems, YOU run on smoke!

That being said, let's talk a bit about safety. It is critical to your safety to make sure that the circuit you are working on has been turned off. This is accomplished in the electrical panel/fuse box. Go there first, identify the appropriate circuit and make sure that it is off.

Also make sure that anyone else in the house is made aware that you are working on the electrical system and they don't accidentally let the smoke out of you by thinking they're merely restoring a tripped breaker. Turn it off, tape it, put a sign on it, or if you want to be a real pro, pick up an inexpensive "Lock-out/Tag-out" kit from the local home center and lock it. You gotta go there anyway to pick up the replacement light switch.

So what were we talking about, oh yea, replacing a bad light switch. Well, lets get with it. It's easy and you can get it done with a single standard screw driver and about 15 minutes.

Once the power has been turned off, remove the wall plate (plastic cover over light switch), then remove the two mounting screws from the light switch, at the top and bottom of the metal frame of the light switch, righty-tighty, lefty-loosie.

Being careful not to touch either of the two screws on the side of the bad light switch (Yet), carefully pull the light switch straight out towards you, there will be some resistance from stiff wires though there should be sufficient slack in the wires to pull the light switch out away from the wall a few inches, enough to work on it.

TEST, TEST, TEST to make sure the power has been turned off to the THIS circuit. You can do this with an inexpensive volt meter, or Non-Contact voltage detector, what we call a "Tic" in the trade. They are cheap (about $15 bucks) can be bought at the same home center you are already going to and will go a long ways to ensuring there is no smoke liberating current present.

I probably have a dozen Tics all over the place and use them almost every day, they're very handy and very cool. Man you are the new BMOC (Google it, I had to) if you have a Tic, trust me, all your buddies (or buddets for you ladies) will drool over it and look on it and you with envy. Besides, you have a legitimate excuse to go to the toy store, oh I mean chore store, sorry hon.

Back to the light switch, you will notice 3 wires attached to the light switch (Only 2 wires in older homes). Two wires will be attached to the side of the light switch and will be either two black wires, or one black and one white wire (Depending on whether it is a switch leg or switch loop, but not important at this point, more below...).

The third wire will be attached to the green screw on the top of the light switch and will be either a bare wire or green wire, this is your ground wire and is the most important wire.

The ground wire should ALWAYS be the first wire on, and the last wire off, this is for your safety as it provides a highly conductive, low resistance path to ground and electricity being lazy, always seeks ground and always via the path of least resistance, meaning that if there is a path to ground more attractive than you, no smoking. But you don't have to worry because you turned the power off right? Just covering basic safe working practices here...

Loosen the two screws on the side of the bad light switch and remove the wires. Now loosen the green ground screw and remove the ground wire, discard bad light switch.

Installing the new light switch is a piece of cake and all you need do is reverse the removal process. You may be wondering, ummm okay, I get the ground wire, there's only one green screw and only one green wire, no brainer. But what happens if you mix up the two wires that came off the side of the old bad light switch? No problem. You see, electrically it doesn't matter at all, you can put either wire on either of the two side screws and it will work just fine (Single Pole switch only for all you pro sparkies out there, but if your a pro and reading this, you have too much time on your hands, give me a call, I've got some wire stretching needs done).

Now just a mental exercise here (Don't actually do this!) but imagine if the power to the circuit was on and you were to touch the two wires from the side of the light switch together, the light would come on, [Angelic voices singing "Ta-da" here]. Anyhow, that's all the light switch does, it touches, or "Closes" the two wires together, completing the circuit, powering on the light.

Reinstall the new light switch back in the wall, re-secure the two mounting screws, replace the wall plate, turn the power back on at the panel, and thats it. Replacing a bad light switch really is a piece of cake.

Now you are for sure the BMOC, got to go to the toy store, have a brand new shiny Tic and your honey has a new open slot on "The List" to fill in and can even see the list now because you fixed the light, maybe you shouldn't have huh...

Cheers and happy & safe home repairing!

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Very helpful. The details are great. Thank you James! By Anthony on 28-04-11 at 07:41pm
Hahaha. I laughed out loud, then I learned something. Then I laughed again. Do you have a youtube channel? If not, Start one! I would Love to SEE the smoke getting let out. But really, thank you. You answered my question. By Stan on 02-05-11 at 10:10pm
Very informative. I was nervous to try this, but now I'll give it a try, after I buy my new toys. Then I'll be the BWOC! Thanks! Jacquelyn By Jacquelyn on 07-05-11 at 10:52pm
I would never have considered doing something like this by myself but now...it doesn't seem so bad. This article makes sense! By Nadia on 07-05-11 at 11:10pm
OK, I'm going to give this a try and I may have more questions. Also, funny! By Chad on 09-05-11 at 09:33pm
I tried this and you’re right it works, thanks there james By Doug on 10-05-11 at 02:59am

Follow-Up Question Don't you have a cover over the ends of the wires? You just wrap them around the screw? (Posted by: Jack )

James P. Oskolkoff Answered by: James P. Oskolkoff, an
expert in the Electrical - General category
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Hi Jack and thanks for your question, it is actually a really good question and has been the subject of some debate over the years.

In case your in a hurry, I'll give you a quick answer;

No additional cover REQUIRED over screws, or exposed wire ends. And yes, you wrap the wires under the screw head in a clockwise direction, starting from the left, so that as you tighten the screw, the screw draws the wire in tight.

Though not required, after securing the wires to the screws, you may, and I have, wrap the entire switch body with a couple layers of electrical tape, covering the terminal screws and exposed wire ends, effectively providing safe coverage. I recommend folding over the last 1/4 inch of tape upon itself providing a handle for ease of removal for the next guy.

Please allow me to elaborate on this issue.

Your observation is correct: the stripped/bare wire ends and the terminal screws themselves are in fact live energized parts and left open or exposed, would pose a significant hazard. This is of course why we insist on de-energizing the entire circuit at the panel prior to any work being performed on the circuit devices, in our case a light switch.

However, once fully & correctly installed inside the junction box or "Enclosure" (definition below) with the wall plate secured in place, both the terminal screws and bare wire ends are considered adequately protected, requiring no additional protection or coverage to the switch body within the enclosure.

Most common residential electrical systems are not considered to be hazardous or "Classified Locations" in accordance with ANSI/UL & ANSI/ISA. Hence there are much less stringent requirements for providing mechanical/contact/arc protection for live exposed parts.

In stark contrast for example would be a gas station (Class 1) where there are either explosive or caustic agents present posing a significant hazard should live exposed parts be present. In such cases as I am sure you can imagine, great care is taken to completely eliminate this possibility in such instances.

Basically, though it may seem a little weird to have bare screws and wires exposed on the switch body while you are holding it in your hand and working on it, it is considered safe once properly installed and covered.

ENCLOSURE Definition, 2008 NEC (NFPA 70) Article 100-1: The case or housing of apparatus (Switch) or the fence or walls surrounding an installation to prevent personnel from accidentally contacting energized parts or to protect the equipment from physical damage.

Thanks again for the great question Jack.

Kindest Regards,

J.P.O.



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