Are these boxes overfull? (USA NEC 2017)

[dogbob]

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!!!

 

[pirate]

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]

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

 

[dogbob]

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]

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]

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