50A range receptacle in 2 gang plastic box

[Rick 0920]

This is a common installation in my area. Most 2 gang plastic boxes are 35 cu. in. A 6-3 w/ground NM cable with the receptacle overloads this box yet I'm seeing it done everywhere. Does anyone else do this and what do the inspectors in your area have to say about it?

 

[infinity]

Do you have a box fill calculation that shows the box being overfilled?

 

[augie47]

Pretty common here.. meets Code.. raco makes a 48 cuin 2 gang box a few folks use.


edit: my error on compliance..used to #8 on ranges

 

[Rick 0920]

Pretty common here.. meets Code.. raco makes a 48 cuin 2 gang box a few folks use.

That would work

 

[Rick 0920]

Do you have a box fill calculation that shows the box being overfilled?

Sure.
3- insulated #6 conductors @ 5.00 cu. in. each
1 - bare #10 EGC @ 2.5 cu. in.
1 - device larger than a standard 1 gang box - (4) #6 conductors @ 5.00 cu. in. each

7 - #6 allowances 7 x 5.00 cu. in. = 35 cu. in.
1 - # 10 EGC 1 x 2.5 cu in. = 2.5 cu. in.
37.5 cu. in.

 

[Dennis Alwon]

Pretty common here.. meets Code.. raco makes a 48 cuin 2 gang box a few folks use.

48 cu in???? The 3" deep we use is 35 cu. in where are they getting the extra 13 cu.in.

 

[Dennis Alwon]

I just googled it and Cantex box is 48 cu. in

https://www.lowes.com/pd/CANTEX-2-Gang-Plastic-New-Work-Electrical-Box/5001729533?cm_mmc=shp-_-c-_-prd-_-elc-_-ggl-_-LIA_ELC_206_Conduit-Fittings-Boxes-_-5001729533-_-local-_-0-_-0&ds_rl=1286981&gclid=Cj0KCQiA1NebBhDDARIsAANiDD24mLALhYXkKZLG0q5YobPTMhFE3Ei8cdrK4npXHSNWhf6HBgYwRH0aAgRkEALw_wcB&gclsrc=aw.ds

I don't see how this is so much larger than the others

 

[augie47]

48 cu in???? The 3" deep we use is 35 cu. in where are they getting the extra 13 cu.in.

RACO 7848

 

[Rick 0920]

I just googled it and Cantex box is 48 cu. in

https://www.lowes.com/pd/CANTEX-2-Gang-Plastic-New-Work-Electrical-Box/5001729533?cm_mmc=shp-_-c-_-prd-_-elc-_-ggl-_-LIA_ELC_206_Conduit-Fittings-Boxes-_-5001729533-_-local-_-0-_-0&ds_rl=1286981&gclid=Cj0KCQiA1NebBhDDARIsAANiDD24mLALhYXkKZLG0q5YobPTMhFE3Ei8cdrK4npXHSNWhf6HBgYwRH0aAgRkEALw_wcB&gclsrc=aw.ds

I don't see how this is so much larger than the others

View attachment 2562909

Dennis, does that box have a 3/4" KO for a Romex connector? It seems you would have to modify it to get a 6-3 w/gr in it. Also, I know it's kind of petty, but if you used that box, you would have to count those internal cable clamps as (1) #6 That information is on Carlon's website FAQ's.

 

[wwhitney]

Also, I know it's kind of petty, but if you used that box, you would have to count those internal cable clamps as (1) #6 That information is on Carlon's website FAQ's.

Do you have a direct reference?

I would be amazed if a molded plastic box's volume calculation doesn't already take into account any clamps molded into it. Since the internal volume of boxes like that is not a cuboid, they can just define and measure the internal volume so that the clamps themselves are outside the measured volume.

Cheers, Wayne

 

[suemarkp]

Doesn't the EGC need to be counted as 5 cubic inches also (same as the #6 ungrounded conductors), and not be based on its #10 size? That would make the fill even larger.

 

[david luchini]

Doesn't the EGC need to be counted as 5 cubic inches also (same as the #6 ungrounded conductors), and not be based on its #10 size? That would make the fill even larger.

Why would the #10 EGC need to be counted as a #6?

 

[suemarkp]

I reread 314.16(B)(5). I see that all grounds count as 1 volume allotment based on the largest equipment ground conductor. I had remembered that as largest conductor, not largest EGC.

 

[infinity]

Sure.
3- insulated #6 conductors @ 5.00 cu. in. each
1 - bare #10 EGC @ 2.5 cu. in.
1 - device larger than a standard 1 gang box - (4) #6 conductors @ 5.00 cu. in. each

7 - #6 allowances 7 x 5.00 cu. in. = 35 cu. in.
1 - # 10 EGC 1 x 2.5 cu in. = 2.5 cu. in.
37.5 cu. in.

Thank you. Although they can be used in a 2 gang box doesn't a single receptacle fit in a single gang box? That would change line #3 in your calculation.

 

[wwhitney]

Thank you. Although they can be used in a 2 gang box doesn't a single receptacle fit in a single gang box? That would change line #3 in your calculation.

I think NEMA 14-50 receptacles have a 2.15" diameter face. As such the yoke is going to be over 2" in width, which is what triggers the jump from 2 allowances to 4 allowances for the device.

Cheers, Wayne

 

[Rick 0920]

Do you have a direct reference?

I would be amazed if a molded plastic box's volume calculation doesn't already take into account any clamps molded into it. Since the internal volume of boxes like that is not a cuboid, they can just define and measure the internal volume so that the clamps themselves are outside the measured volume.

Cheers, Wayne

Wayne, I will try to post a pic of the actual page that I printed from Carlon's website. It refers to the FAQ's on the Zip Box Blue switch and outlet boxes.

 

[infinity]

I think NEMA 14-50 receptacles have a 2.15" diameter face. As such the yoke is going to be over 2" in width, which is what triggers the jump from 2 allowances to 4 allowances for the device.

Cheers, Wayne

Many have three mounting holes top and bottom which accommodates either single or two gang mounting. If it doesn't have the center hole then it would probably require the double deduction.

 

[Barney B]

Thank you. Although they can be used in a 2 gang box doesn't a single receptacle fit in a single gang box? That would change line #3 in your calculation.

Rick's box fill calculation at post #5 is correct and complete.
1. The volume of the clamp area (and the clamps) in a non-metallic box is excluded from the volume marked by the manufacturer. See the last sentence of the second paragraph of 314.16(B)(2).
2. A range receptacle is wider than 2.00" and thus requires double allowances for the yoke, despite the fact that Infinity can cram it into a 1-gang box. Leviton for example shows their version to be 2.42" wide. See the last sentence of 3.114.16(B)(4).

 

[wwhitney]

Many have three mounting holes top and bottom which accommodates either single or two gang mounting. If it doesn't have the center hole then it would probably require the double deduction.

The wording in 2017 NEC 314.16(B)(4) is "A device or utilization equipment wider than a single 50 mm (2 in.) device box as described in Table 314.16(A) shall have double volume allowances provided for each gang required for mounting."

I agree now that if you find a NEMA 14-50R that says it can be mounted in a single gang box, even though it is wider than 2", then it only requires one double allowance. Some of them say not to mount in a single gang box, in which case I would say they require two double allowances.

So that is one way to use a 35 in^3 double gang box, find a 14-50R that says it's OK to mount in a single gang box. It obviously still wouldn't fit in a single gang box, but I guess the labeling means you could use a single gang mud ring on a 4" square box.

Cheers, Wayne

 

[Rick 0920]

Thank you. Although they can be used in a 2 gang box doesn't a single receptacle fit in a single gang box? That would change line #3 in your calculation.

The code section refers to receptacles wider than a standard single gang box. But based on the fact that you CAN install it in a single gang box, the double volume allowance would be correct. But I might add that you probably want the extra wire bending space for #10, #8 and #6 conductors.