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DangerMouse 07-19-2008 09:59 AM

wiring outlet boxes, steel or plastic?
hi everyone
i'm using 12/2 under a crawl space stapled every 12" or so to power 8 outlets in a new addition room,then running up a new wall stud to attic joist junction box, to be powered up after inspection. all outlets are gfic's rated 15a but i need to understand code a bit better to be assured i will not need to rip out anything and redo a job! so, if i use 12/2 to all outlet boxes, using metal boxes means the screw that mounts the frame of the outlet to the box will ground the box, yes? or will he tell me to add a screw and wire? and the plastic boxes say pvc SWITCH boxes, so i should not use them for outlets at all? the back porch light will be 14/2 from the outlet box, to the light switch on to the outside light (rated 60w max) my reason for running all 12/2 is somewhere down the line, someone may plug in something higher amps/watts, etc. i figure if i use all 12/2 i can go beyond code a bit and stay a little safer?
tnkx for listening

Stubbie 07-19-2008 10:15 AM

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The answer to your question is not a simple one with regard to the metal boxes. The plastic ones you just connect to the green screw on the yokes of the devices with a pigtail from the equipment ground of your cables.
To make it simple and not go through all the options for your metal boxes you will have one threaded screw hole in the back of the box. You need to get some green grounding screws then connect a pigtail from the wirenut with the equipment grounds of the cables to the metal box using the green grounding screws also a pigtail to the grounding screw of the switch or receptacle.

The image I have attached gives the general idea with a metal box and various cables entering and leaving there are alternatives but this will get you through any inspection. Try not to get to many cables going to a box. Keep it simple. Lots of cables entering a box creates box fill issues and it may be difficult to connect all your wires into a wirenut as a DIY. If you run into problems with too many wires use a push in connector found at the big box stores in place of a wirenut. You may even want to use them in place of wirenuts. They come with up to 8 ports.

DangerMouse 07-19-2008 10:46 AM

i planned on using 4 outlets on each run left and right around the room, then just the two lines into the junction box to splice to breaker box. line in, load out to each recep should be ok, yes? (oh, then the one line off the outlet to the porch light) so each outlet box will only have 2 wires to and from it. my problem with the plastic boxes is strength i guess, they hammer in diag. to a stud and just seem too flimsy for an outlet. so i should just go BUY some premade pigtails or would the inspector be ok with copper looped and screwed through with a flathead screw?

Stubbie 07-19-2008 10:55 AM

There is nothing wrong with the plastic boxes if you want to use them. They are plenty strong enough. I would reccommend pvc blue carlons. Caution though be sure to mount them so they will be flush with the finished wall (drywall or whatever). There is usually a guide on the side of the box for 1/2" drywall.

Making your own pigtails out of bare is fine, your screw will need to be a 10-32 machine thread but I would just go get a box of the green grounding screws at HD or Lowes.


planned on using 4 outlets on each run left and right around the room, then just the two lines into the junction box to splice to breaker box. line in, load out to each recep should be ok, yes?
Yeah that's ok but you cannot bury that junction box it must remain accessible. I would just run my homerun to the first receptacle box then out of it for my other receptacles and then use another receptacle box to catch power for my lights.

Stubbie 07-19-2008 11:04 AM

I just noticed you said you are going to run 14/2 out of the junction box/receptacle box. No can do that. You must not change wire size from 12/2 to 14/2 at the box.. the inspector ain't gonna like that even if your breaker is 15 amp.

DangerMouse 07-19-2008 11:09 AM

that's what i meant, line in, load out outlet to outlet down each run, then the two lines will join in a rafter-mounted junction box above the expected level of blown-in insulation of approx. 10" then wirenutted to a single line to the breaker box. i also wanted to add a ceiling fan, so should i add another line or could it join in this outlet party? and end in the aforementioned junction box? too much? lol
tnkx for helping me out here stubbie!

DangerMouse 07-19-2008 11:23 AM

oops, not the junction box! i meant the last outlet has 12/2 going in, but 14/2 on the last leg up to the light switch box and on to the light bulb. this is a nono? what the heck is 14/2 FOR if not for luminaries? wall outlets? overhead room lights? basement lights? gas dryer? that's what the wire box sez... then 12** for a lot of other uses that can be either/or..... darn cornfussing!
i just want to be DAM sure i do this right the FIRST time.. =o)

Stubbie 07-19-2008 11:24 AM

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I think you would be smarter to run a 15 amp 14/2g branch circuit for the lights and fan. And a 12/2 g 20 amp branch circuit for the receptacles and forget a jb in the attic. but your way will work and you certainly could add the fan.

Is this what you are wanting to do.....

DangerMouse 07-19-2008 11:32 AM

yes, that's certainly close, but my problem is with the inspector. he needs to see all the wiring done correctly before i can close my walls up and mud and paint the drywall walls and ceiling. so i figure if i run both lines ( i COULD just loop all around under the room and make it ONE run of 8 outlets?) and he sees it end in the junction box, i can proceed.


Stubbie 07-19-2008 11:37 AM

Branch circuit wiring should be all the same guage unless we are considering voltage drop. Just because you are running to a light from the receptacle which is served on 12/2 does not mean you can use 14/2. The only way you can do this is if the breaker is 15 amps. So you basically have wasted the cost of the 12/2 and the power you can utilize with it. 12/2 = 20 amps 14/2 = 15 amps.

If your breaker is 15 amps then just run 14/2 all the way, the 12 is unecessary.

Again I suggest you run a 15 amp 14/2G circuit to the fan and outside lights and a 12/2G 20 amp branch circuit for your receptacles and ditch the jb in the attic.

Stubbie 07-19-2008 11:54 AM

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This is what I suggest or something similar. Why jb in an attici if it isn't necessary?

DangerMouse 07-19-2008 12:11 PM

ok, tnkx
i'll replace the 3 ft. of 14/2 with 12/2 to the outside light, and do the fan separately.

DangerMouse 07-19-2008 12:18 PM

junction box waiting in plain sight up there is easiest for the guy to see so i can continue with just that room, and wiring thru the attic space while it's open seemed to be easier than crawling thru a dirty crawlspace is all. when i'm finished, i'll install a new breaker box and add the new branches. the attic will be non-accessible. so i THINK i'm good to go now? =o)


Stubbie 07-19-2008 12:35 PM

Your welcome good luck with your inspection....:thumbsup:

DangerMouse 07-19-2008 12:54 PM

one last question..... the plastic blue boxes say outlet/switch, the gray says only SWITCH, hence i cannot use the gray for outlets?


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