Junction Box Grounding Issues


Old 01-16-06, 12:39 AM
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Join Date: Jan 2006
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Question Junction Box Grounding Issues

Hi everyone,

I just bought my first home last month and this is my first post. I am remodeling the attic. Currently there is 1 outlet to supply all the power and is overloaded on the circuit. I want to add 6 new receptacles. I purchased a 15 amp breaker and 14-2 wire at Home Depot. I have successfully put up all my drywall and put blue plastic junction boxes where the receptacles are to be as well as 2 junction boxes in the crawl space to splice the wires. I have run the wires to the boxes, however I have not connected any of the receptacles, wires in the 2 junction boxes or the wire to the panel box because I am clueless on how to ground the wires with the plastic junction boxes. All I have seen on the internet is how to wire them with metal boxes. I am thinking I should have just purchased metal ones and I would have power by now . Any help or diagrams would be greatly appreciated.
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Old 01-16-06, 05:29 AM
Join Date: Sep 2003
Location: Central New York State
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You should have purchased 12 gage wire and a 20 amp breaker. It makes no sense to add a 15 amp circuit when a 20 amp circuit is only a little bit more expensive and supplies one third more power.

Plastic junction boxes don't get grounded. The ground wires get connected together and pigtailed to the receptacle.

Why did you place two extra junction boxes? To minimize the connections, you should only have them at the receptacles themselves. Extra junction boxes increase the chances of a problem down the road. Make sure that these extra junction boxes are permanently accessible and are covered with a blank cover plate. Or better yet, stick a receptacle in them and use them.
Old 01-16-06, 07:45 AM
Join Date: Sep 2000
Location: United States
Posts: 18,497
Please, for your own sake, obtain and thoroughly read three books on home wiring before proceeding. You can purchase such books at most home centers, or you can check them out at most public libraries. There's a lot more you need to know than you think you do.
Old 01-16-06, 08:00 AM
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Join Date: Dec 2005
Location: Warren, Vermont
Posts: 353
14 ga. cable.

I have to speak up in defense of 14 ga. cable, because I feel that Racecraft's opinions were a bit too strong. There are times when it does make sense to use 14 ga. cable, and this may be one of them. You stated that you are remodeling your attic. You did not say how big it is. You did state that there is power, but only to one receptacle. Although you did not tell us if there were going to be any special loads that you are planning to use on this circuit, it does sound as if a 15 amp circuit could be quite sufficient for this situation.

A 14 ga. cable is easier to work with and sometimes makes the difference on the number of cables that can enter a box. If 12 ga. cables are used, it could require a bigger box, or maybe an extra box somewhere, to accomodate the larger fill requirement.

In a remodel, it is often very difficult and at times impossible to run cable from box to box around a room. Extra junction boxes are very appropriate for those situations. If these junction boxes are in the kneewall crawl space, I don't see where adding an outlet to them makes much sense. You would have to add a pigtail to your wire nuts, which could increase the chances of a poor connection, especially trying to wire in a small crawl space.
Be sure to tug on every wire under every wire nut before you tuck into the box, to be sure that they are not going to slip out of the nut.

Although plastic boxes do not require any grounding to the box and are less expensive, they do break and the threads for the device screws strip easily. They do not rust, but they are not gangable, and there is no means to clamp a cable to the box. They do require an extra pigtail to every switch, where a switch in a metal box does not require that pigtail.
Old 01-16-06, 11:05 AM
Join Date: Jan 2006
Location: Michigan
Posts: 34
I always use 20 Amp Breakers, 20 Amp Receptacles, and 12/2 with Ground now. I spend a little extra for the higher density Carlon Blue Plastic box and always try to get the one with extra depth to permit room for interconnection behind receptacles. The box is strong, secure, and with more depth is a great solution to the 12 gauge ability to bend. Make sure all grounds are connected together in each box and that you supply a ground wire to the receptacle and/or switch green screw. One more thing, IMO avoid using the rear slots to terminate receptacles. Utilize the screws and throw a line of tape around the receptacle to ensure no accidental shocks. Those little slots dont hold the wire tension so well when you put it back into box.
Old 01-16-06, 11:20 AM
Join Date: Jul 2005
Posts: 131
12 won't fit in the backstab holes anyway.
Old 01-17-06, 03:07 PM
Join Date: Apr 2004
Location: Ontario Canada
Posts: 1,767
You don't use backstabs anyway. You use back wire or side-screw.
Old 01-17-06, 04:03 PM
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I personally feel the "I ONLY use #12" stance is a macho thing. Please do not start a flame war, this is simply my opinion.

I totally agree with fixatron. I never use #12 for lighting unless the circuit mandates it.
If you do this stuff long enough you'll realize; 3 and 4 gang boxes, dimmers and 3&4 ways are NOT very #12 friendly.
Old 01-17-06, 06:38 PM
itsunclebill's Avatar
Join Date: Jan 2006
Location: Denver, CO area
Posts: 221
I've broken way too many "clamps" in Carlon boxes to be happy with them. I only use them when nothing else will work. As to taping receptacles, you only need to if you're workin' 'em hot. If the tape is to keep the receptacle from shorting to a metal box you need to work on technique a bit. If the wire is coming out of backSTABs, well, that's backstabs. If it's coming out of a backFED termination the screw isn't tight enough. If the screw is stripping before you get the clamp tight enough to hold the wire you need to spend another quarter/50 cents and get a decent receptacle.

I agree with Petey 100%. I'd rather run 2 #14 circuits than deal with #12 on dimmers and in double, tripple, and fourful boxes. Again, MY opinion.


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