Discuss Are these boxes overfull? (USA NEC 2017) in the Electrical Forum area at ElectriciansForums.net

dogbob

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I am a homeowner-to-be. This is in USA, and must follow NEC 2017 (this state has not yet adopted 2020). The builder has done rough electrical and it concerns me, but I am not an electrician, so can't make a definitive call.

In the attached photo, the left box appears to be a 32 cu in box (is that correct?) and already has four NM cables coming in the top and at least two coming in the bottom. I think that white is 14-3 and yellow is 12-3. I don't know about the bottom. The way I read NEC 314.16, a 32 cu in box can only have 13 #12 conductors, and then no outlets. The top is already 9 #12 and 3 #14, and there are also wires from the bottom and probably going to be one or two outlets (yokes?).

The right box appears to be a 16 cu in box (is that correct?) and has 3 or 4 NM 14-3 cables (two on far right, one or two on left) giving 9 or 12 #14 conductors, but I think we are limited to 7, and again, that doesn't allow an outlet.

Am I interpreting this correctly? Am I missing anything?

Thank you!!!
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James

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In my humble opinion, I would not consider that to be “rough electrics”
it looks quite neat and tidy.

I think the person doing that work has done quite a lot of electrical work in the past and may well be a perfectly good electrician.

if you have concerns, bring them to the attention of the builder/lead contractor in writing and await their response.

edit,

I am uk based and understand some of the differences between uk and USA wiring code but not all of it.

@Megawatt is a USA spark that regularly posts good quality info about things your side of the pond.
 

Lucien Nunes

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UK peeps: This is something specific to the NEC. There are strict limits on the number of cables and conductors of any size that may be terminated in any size of box. You have to know the box volume in cubic inches and use a table or a formula to work out what it can hold.

Personally I don't like the idea, I consider myself a better judge of how accessible and maintainable my termination work is, than a table in a book. But it does stop people just ramming stuff in until it's completely unworkable, such as we often see with heating systems, because it becomes a violation not just poor style.
 

Megawatt

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I am a homeowner-to-be. This is in USA, and must follow NEC 2017 (this state has not yet adopted 2020). The builder has done rough electrical and it concerns me, but I am not an electrician, so can't make a definitive call.

In the attached photo, the left box appears to be a 32 cu in box (is that correct?) and already has four NM cables coming in the top and at least two coming in the bottom. I think that white is 14-3 and yellow is 12-3. I don't know about the bottom. The way I read NEC 314.16, a 32 cu in box can only have 13 #12 conductors, and then no outlets. The top is already 9 #12 and 3 #14, and there are also wires from the bottom and probably going to be one or two outlets (yokes?).

The right box appears to be a 16 cu in box (is that correct?) and has 3 or 4 NM 14-3 cables (two on far right, one or two on left) giving 9 or 12 #14 conductors, but I think we are limited to 7, and again, that doesn't allow an outlet.

Am I interpreting this correctly? Am I missing anything?

Thank you!!!
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first off go to article 316.16(A) and 314.26(B) to get your answer. Each #12 is 2.25 cubic inches each #14 is 2.00 cubic inches, count the largest ground as 1 # 12 count it as one wire which is 2.25 cubic inches, and add 2.25 cubic inches for the yoke Having said that the cubic inches for the box should be stamped in the bottom of the box. The box on the left which is a 3 gang box that has that many cables that each have 3 wires and the devices count as one #12. The math would be 12 times 2.25 cubic inches equals 50 cubic inches with the #12 wires and #14 which is counted as 2.00 cubic inches and 1 # 12 ground and count 1 yoke at 2.25 cubic inches. Add all the single wires plus the yokes and then find the correct size of your box which at most is 4 11/16 times 2 1/8 is the biggest box. I’m coming up with 31.5 cubic inches just for the # 12 wires and yoke plus the ground and 18 cubic inches for the 14 wires and that’s just adding the top and not the bottom. Why in the hell is the builder and not an electrician doing the rough in anyway. With using that many wires for a simple 3 gang box is stupid. That box would never pass inspection. Hire you a qualified electrician to straighten that mess up. The biggest 4 inch square box they make is the most cubic inches that you can use is 4 times 11/16 by 2 1/8 which is only good for 42 cubic inches period. The box on the right should be fine but it’s also close on your box fill

so it’s safe to say that box has way to many wires to be in compliance with the NEC. If you really want to learn study article 314. There is no way that 3 devices in a 3 gang box can use that many wires. It’s way to early in the morning to get my brain to function without my coffee. Simple terms study article 314 to get your answers. Let us know how it turns out. Good luck my friend. I hope that this helps you and with all them wires you would have to cram all them wires in the box much left the 3 devices. The 14/3 shouldn’t even be in that box since it will serve as another circuit. @littlespark and when I first wake up I’m brain dead. LOL
 

Megawatt

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first off go to article 316.16(A) and 314.26(B) to get your answer. Each #12 is 2.25 cubic inches each #14 is 2.00 cubic inches, count the largest ground as 1 # 12 count it as one wire which is 2.25 cubic inches, and add 2.25 cubic inches for the yoke Having said that the cubic inches for the box should be stamped in the bottom of the box. The box on the left which is a 3 gang box that has that many cables that each have 3 wires and the devices count as one #12. The math would be 12 times 2.25 cubic inches equals 50 cubic inches with the #12 wires and #14 which is counted as 2.00 cubic inches and 1 # 12 ground and count 1 yoke at 2.25 cubic inches. Add all the single wires plus the yokes and then find the correct size of your box which at most is 4 11/16 times 2 1/8 is the biggest box. I’m coming up with 31.5 cubic inches just for the # 12 wires and yoke plus the ground and 18 cubic inches for the 14 wires and that’s just adding the top and not the bottom. Why in the hell is the builder and not an electrician doing the rough in anyway. With using that many wires for a simple 3 gang box is stupid. That box would never pass inspection. Hire you a qualified electrician to straighten that mess up. The biggest 4 inch square box they make is the most cubic inches that you can use is 4 times 11/16 by 2 1/8 which is only good for 42 cubic inches period. The box on the right should be fine but it’s also close on your box fill

so it’s safe to say that box has way to many wires to be in compliance with the NEC. If you really want to learn study article 314. There is no way that 3 devices in a 3 gang box can use that many wires. It’s way to early in the morning to get my brain to function without my coffee. Simple terms study article 314 to get your answers. Let us know how it turns out. Good luck my friend. I hope that this helps you and with all them wires you would have to cram all them wires in the box much left the 3 devices. The 14/3 shouldn’t even be in that box since it will serve as another circuit. @littlespark and when I first wake up I’m brain dead. LOL
Heck I read all that and it confuses me but if he uses the charts and learns them he will be fine. I’m going to drink my coffee. Good question @littlespark especially when you first wake up but thank you for the heads up
 

Megawatt

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first off go to article 316.16(A) and 314.26(B) to get your answer. Each #12 is 2.25 cubic inches each #14 is 2.00 cubic inches, count the largest ground as 1 # 12 count it as one wire which is 2.25 cubic inches, and add 2.25 cubic inches for the yoke Having said that the cubic inches for the box should be stamped in the bottom of the box. The box on the left which is a 3 gang box that has that many cables that each have 3 wires and the devices count as one #12. The math would be 12 times 2.25 cubic inches equals 50 cubic inches with the #12 wires and #14 which is counted as 2.00 cubic inches and 1 # 12 ground and count 1 yoke at 2.25 cubic inches. Add all the single wires plus the yokes and then find the correct size of your box which at most is 4 11/16 times 2 1/8 is the biggest box. I’m coming up with 31.5 cubic inches just for the # 12 wires and yoke plus the ground and 18 cubic inches for the 14 wires and that’s just adding the top and not the bottom. Why in the hell is the builder and not an electrician doing the rough in anyway. With using that many wires for a simple 3 gang box is stupid. That box would never pass inspection. Hire you a qualified electrician to straighten that mess up. The biggest 4 inch square box they make is the most cubic inches that you can use is 4 times 11/16 by 2 1/8 which is only good for 42 cubic inches period. The box on the right should be fine but it’s also close on your box fill

so it’s safe to say that box has way to many wires to be in compliance with the NEC. If you really want to learn study article 314. There is no way that 3 devices in a 3 gang box can use that many wires. It’s way to early in the morning to get my brain to function without my coffee. Simple terms study article 314 to get your answers. Let us know how it turns out. Good luck my friend. I hope that this helps you and with all them wires you would have to cram all them wires in the box much left the 3 devices. The 14/3 shouldn’t even be in that box since it will serve as another circuit. @littlespark and when I first wake up I’m brain dead. LOL
I need to edit the articles with the chart 314.16(A) and chart 314.16(B) for box fill calculations
 
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dogbob

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Great advice, detailed and helpful. Thank you.

Yes, I've read 316.16(A) and 314.26(B), and that's why I was concerned. But I'm just a tinkerer and this work was done by a professional electrician, so I wanted a real opinion before raising my concerns. But they will be drywalling soon and burying any errors.

Unfortunately, I am 1500 miles away from the project. I can't look at the boxes to read the sizes/specs. I had one opportunity for a very dear friend to stop by and take photos at random and am trying to figure out what I'm seeing.

By the way, why did you call the left box "three gang"?

Again, thanks!
 
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dogbob

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I found one more photo of that area, zoomed in (below). It gives a bit more detail on the number of wires going into the bottom and the stuffing.

This box is behind the refrigerator in the kitchen. I think that the smaller box (shown above but not shown below) is power for the refridgerator. This larger box may be solely interconnect. I don't think there is a reason for another outlet there.

Unfortunately, the house plan that I have (below) only shows user features, not construction details. The photo was taken while in the kitchen, looking to the right. I drew a blue square for the location of this photo.
 

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Megawatt

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I found one more photo of that area, zoomed in (below). It gives a bit more detail on the number of wires going into the bottom and the stuffing.

This box is behind the refrigerator in the kitchen. I think that the smaller box (shown above but not shown below) is power for the refridgerator. This larger box may be solely interconnect. I don't think there is a reason for another outlet there.

Unfortunately, the house plan that I have (below) only shows user features, not construction details. The photo was taken while in the kitchen, looking to the right. I drew a blue square for the location of this photo.
Maybe that box is designed for a junction box but it is still over the box fill calculations which is in violation of the NEC
 

Dustydazzler

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In my humble opinion, I would not consider that to be “rough electrics”
it looks quite neat and tidy.

I think the person doing that work has done quite a lot of electrical work in the past and may well be a perfectly good electrician.

if you have concerns, bring them to the attention of the builder/lead contractor in writing and await their response.

edit,

I am uk based and understand some of the differences between uk and USA wiring code but not all of it.

@Megawatt is a USA spark that regularly posts good quality info about things your side of the pond.
Funny old Americans / Canadians always seem to call their first fix wiring 'rough house wiring' or 'roughing in wiring'
 

Megawatt

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Funny old Americans / Canadians always seem to call their first fix wiring 'rough house wiring' or 'roughing in wiring'
@Dustydazzler even the inspectors call it a rough in inspection which you have to have so the drywall people can start installing there sheet rock. It is tidy work, its just a violation and who knows what else they did that we haven’t seen. Have a great day
 

Dustydazzler

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Yes I know it is an actual phrase you use 'roughing in the wiring' for what we call 'first fixed' wiring

Here in the UK if you said to someone that you were going to be roughing in some wiring they would presume you were making a mess and just throwing in the wiring with no care
 
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dogbob

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"It is tidy work, its just a violation and who knows what else they did that we haven’t seen."

Yes, that's my bigger fear. Who knows what evil lurks in the dark corners?
 

pirate

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Genuinely interested to learn from this. Why the concern over number of cables? is it a heat thing? I have to say I think the installation looks quite neat. I accept that "neat" does not mean "compliance" and have no knowledge of the regs in the USA, hence my query.
Is the purpose of the circuits irrelevant? By that I mean, is it the current flow that dictates the "fill" ratio?
For me, every day's a school day, so I would really like to know more.
 

Dustydazzler

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The NEC has lots of 'interesting' codes , like you have to staple a cable xyz inches from a box etc
There are entire youtube videos explaining 'the code' and with example of code violations

If you are ever struggling to sleep they will send you off within 20 mins
 
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dogbob

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I just redid the math using what I think is correct, for what I think is going on.
From the two photos, it appears that this box has 4 gray cables, 3 yellow cables, & 1 white cable.
Yellow is commonly 12-2+G and white is commonly 14-2+G. Gray is underground cable, with nonspecific gauge. Assuming gray is also 12-2+G, we need:
14*2.25+2*2=35.5 for conductors
2.25+4*(2.25/4)=4.5 for grounds
2.25 for internal clamping
With no recepticles, that's 42.25 cubic inches.
I found something on the web (Cantex EZ48DNR) that looks like this box and is 48 cu in.
If they really used a 48 cu in box, could it be that this is good?

If they add two recepticles, however, that's 4.5 cu in each, for another 9 cu inches, and certainly over budget.
If they used a 42 cu in box or smaller, again over budget.

To Pirate's question, the calculations in the NEC do not take into account load, only wire size. I've not been able to find a specific reason for box fill limitations, other than to prevent unsafe conditions.
 

Megawatt

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Great advice, detailed and helpful. Thank you.

Yes, I've read 316.16(A) and 314.26(B), and that's why I was concerned. But I'm just a tinkerer and this work was done by a professional electrician, so I wanted a real opinion before raising my concerns. But they will be drywalling soon and burying any errors.

Unfortunately, I am 1500 miles away from the project. I can't look at the boxes to read the sizes/specs. I had one opportunity for a very dear friend to stop by and take photos at random and am trying to figure out what I'm seeing.

By the way, why did you call the left box "three gang"?

Again, thanks!
I called 3 gang because if you look in the box it’s has across the top 3 screw holes and the same on the bottom which it will accommodate 3 separate devices. My friend even if a receptacle is to go in that box I don’t think you could cram the wires in the box plus the receptacle. You asked about box fill and what’s it for. For one thing they all are current carrying conductors in a race way which In lay mans terms is that electrical causes heat. Add a couple of boxes close to that box so when you run across a problem with the 4x4 you will have a plan B. Again good luck
 

Megawatt

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I just redid the math using what I think is correct, for what I think is going on.
From the two photos, it appears that this box has 4 gray cables, 3 yellow cables, & 1 white cable.
Yellow is commonly 12-2+G and white is commonly 14-2+G. Gray is underground cable, with nonspecific gauge. Assuming gray is also 12-2+G, we need:
14*2.25+2*2=35.5 for conductors
2.25+4*(2.25/4)=4.5 for grounds
2.25 for internal clamping
With no recepticles, that's 42.25 cubic inches.
I found something on the web (Cantex EZ48DNR) that looks like this box and is 48 cu in.
If they really used a 48 cu in box, could it be that this is good?

If they add two recepticles, however, that's 4.5 cu in each, for another 9 cu inches, and certainly over budget.
If they used a 42 cu in box or smaller, again over budget.

To Pirate's question, the calculations in the NEC do not take into account load, only wire size. I've not been able to find a specific reason for box fill limitations, other than to prevent unsafe conditions.
Good job with the math but you just have to count the grounds as one wire which will be sized as the ground for the largest conductor which is # 12
 

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