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Old 12-02-2013, 11:04 AM
 
32 posts, read 33,364 times
Reputation: 22
Default Extension Cord Safety Concerns

I only know that a person is not supposed to do this, but I don't know why. I'm hoping someone can give me a good, clear explanation as to why and what the dangers are. Or, point me to a website that gives a lot of info on this subject.

When using extension cords outside for Christmas lights/decorations, why should you not do the following:

1) Use a indoor only regular extension cord
2) Plug a 3 prong outdoor extension cord into a 2 prong indoor only extension cord
3) Fail to adequately tape the connection between the 3 prong outdoor extension cord and 2 prong indoor only extension cord


I know that at my house, doing any of the following would probably work fine until it rained. Then it would probably "trip" the GFCI in the upstairs bathroom. Although, I'm not sure if the grounding prong needs to be connected to the outlet for the GFCI to be tripped.


But I know that not all houses are wired the same and some don't even have a GFCI installed, so I don't know what would happen in those cases. The reason I'm asking is because my grandfather did all the things listed above when he and my uncle hooked up some new outside Christmas decorations. Oddly, my grandfather used to work as an electrician. He didn't know what the grounding prong was used for and if it was necessary to be plugged in. WTF?
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Old 12-02-2013, 02:44 PM
 
Location: Somewhere in northern Alabama
11,490 posts, read 25,992,256 times
Reputation: 14011
I suspect the decorations only have two wires coming from the device plug and going to the lamp. In such a case, the ground in the outdoor extension cord would be superfluous. Most decorations are fairly low wattage, so for the month or so they are up, a newer indoor cord isn't going to have much deterioration from weather or UV light. Older ones get brittle and expose the conductors. I suppose you could tape connections, but more water tends to get trapped under tape than if the connection is left as is. If you look at it fatalistically, if the system doesn't work, you get to spend Christmas with Jesus.
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Old 12-02-2013, 03:05 PM
 
Location: Pittsburgh
3,312 posts, read 1,849,280 times
Reputation: 3620
Quote:
Originally Posted by harry chickpea View Post
If you look at it fatalistically, if the system doesn't work, you get to spend Christmas with Jesus.
Maybe, but sending the postman or someone on ahead of you probably isn't in the spirit of the season.

At the very least, I'd not use an indoor cord if I was running it across the ground. I agree about the tape. Far better to make sure your connections are in places where water can't pool.
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Old 12-02-2013, 03:48 PM
 
1,063 posts, read 411,181 times
Reputation: 1143
Quote:
Originally Posted by mej1 View Post
I only know that a person is not supposed to do this, but I don't know why. I'm hoping someone can give me a good, clear explanation as to why and what the dangers are. Or, point me to a website that gives a lot of info on this subject.

When using extension cords outside for Christmas lights/decorations, why should you not do the following:

1) Use a indoor only regular extension cord
2) Plug a 3 prong outdoor extension cord into a 2 prong indoor only extension cord
3) Fail to adequately tape the connection between the 3 prong outdoor extension cord and 2 prong indoor only extension cord


I know that at my house, doing any of the following would probably work fine until it rained. Then it would probably "trip" the GFCI in the upstairs bathroom. Although, I'm not sure if the grounding prong needs to be connected to the outlet for the GFCI to be tripped.


But I know that not all houses are wired the same and some don't even have a GFCI installed, so I don't know what would happen in those cases. The reason I'm asking is because my grandfather did all the things listed above when he and my uncle hooked up some new outside Christmas decorations. Oddly, my grandfather used to work as an electrician. He didn't know what the grounding prong was used for and if it was necessary to be plugged in. WTF?
If your lights are plugged into a GFCI (Ground-Fault Circuit Interrupt) then, assuming your GFCI works, you are enjoying a high degree of equipment protection from electrocution - but I don't like to rely on the safety mechanism of my guns any more than a $5.00 GFCI that was manufactured by the lowest bidder in China.

1) "Indoor only" extension cords are minimally insulated, not made with UV resistant materials and not rated for moist environments. You can use them outdoors if you like, but they labeled it clearly so you can't sue them if you get hurt or burn something down.

2) If you have a device that has a three-prong male plug, it is designed to be operated with a ground connection (which is the whole purpose of the third hole/prong); the casing will not be insulated but will instead be connected to the "3rd prong" via a grounding screw or a weld/solder/etc. etc. In this manner, if there is a short in the wiring of the device then (in theory) the current passing from the hot-wire to the ground wire will exceed the pass rating of the circuit breaker and the breaker will trip, thereby alerting you to a problem with the device. If the casing of the same device with the same short circuit is not connected to ground, when you touch the casing YOU may become the ground (which would suck). If, on the other hand, you have 2-prong lights plugged into a 3-prong extension cord which is then plugged into a 2-prong extension cord, that's not a problem. I could explain why, but it's easier to simply say "Don't plug a three-prong device into a two-prong outlet/cord" since that covers my arse as far as liability for your electrocution death is concerned.

3) The ground wire doesn't carry current unless there is a problem with a grounded device plugged into it. You don't need to tape the third prong (which is beside the point since you generally shouldn't be using it with a 2-prong cord).

You should just go to home depot and buy some outdoor extension cords.
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Old 12-02-2013, 07:54 PM
 
4,534 posts, read 2,496,026 times
Reputation: 4659
Indoor extension cords are thin jacketed and easily damaged. Since they have no ground prong if the jacket in was damaged and you grabbed it you become the ground. You'll see Jesus for a second I guarantee you.
is your life worth more than $35? Because that's how much a good 12ga extension cord costs.
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Old 12-02-2013, 08:00 PM
 
Location: Pittsburgh
3,312 posts, read 1,849,280 times
Reputation: 3620
Quote:
Originally Posted by Electrician4you View Post
is your life worth more than $35? Because that's how much a good 12ga extension cord costs.
You need to multiply the $35 by the probability of dying and then compare that to how much you value your life. So, if you value your life at $1,000,000, then you'd buy the right cord if you figured the increased odds of dying are around 30,000 times. I don't know what the exact odds are in real life, but I'd never use an interior extension cord outside either.

Of course, if people did those kinds of calculations, they'd probably not bother to hang Christmas lights.
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Old 12-02-2013, 08:47 PM
 
Location: Spring Hill, Florida
1,412 posts, read 1,205,003 times
Reputation: 1236
In today's litigious society, if some neighborhood kids decide to screw with your Christmas lights and get a good zap - you could find yourself on the receiving end of a lawsuit after the resulting investigation reveals use of an indoor extension cord outside or some other unsafe condition. Stranger things have happened - burglars or their families have sued homeowners who were injured/killed after breaking into a home.
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Old 12-03-2013, 09:20 AM
 
3,464 posts, read 2,756,985 times
Reputation: 5227
Quote:
Originally Posted by mej1 View Post
...When using extension cords outside for Christmas lights/decorations, why should you not do the following:

1) Use a indoor only regular extension cord
2) Plug a 3 prong outdoor extension cord into a 2 prong indoor only extension cord
3) Fail to adequately tape the connection between the 3 prong outdoor extension cord and 2 prong indoor only extension cord
Basically plugging all the outdoor lights/extension cords into a GFCI outlet will make all the wiring safe from electrocution for people and animals. That will "trip" should there be a "leak to ground" (someone is being shocked) and will do so in a fraction of a second before the person even knows they are being shocked.

Other than that, for #1: Outdoor rated electrical devices are designed to keep the water out.

For #2: The 3rd prong on electrical gizmos and appliances is mostly for those which have a metal case. Like a range, washing machine, drill, electric tools, etc. With those an electric wire inside the gizmo/tool/appliance can come loose and touch the metal case. Then a person can touch the metal case and be electrocuted.

For safety that metal case is connected to the 3rd prong of the plug (ground). That 3rd prong needs to also be connected all the way to the electric outlet, then you are protected. (Breaker will trip and the electrical potential will be held at ground.) If you have a 2 prong cord in the mix, that 3rd connection will not be connected to the outlet ground - this can result in dangerous situation should the electrical gizmo develop a short/fault to its metal case.

In the case of gizmos and electrical devices which do not have a 3rd prong, the third prong on an extension cord they are plugged into would not be needed.

For #3: In my experience taping a cord plugged into another cord does nothing so far as keeping the connections dry. Actually it may allow water to collect inside and not drain away!

Better would be to not tape and use a GFCI outlet. Or wrap plastic over the top of the connection with a drain hole in the bottom so water can drain out (should any get in). (Or use something specifically designed to keep the connections dry.)

Further reading...
http://en.wikipedia.org/wiki/Ground_(electricity)

Appliance classes - Wikipedia, the free encyclopedia
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