50A range receptacle in 2 gang plastic box

Status
Not open for further replies.
R

Rick 0920

Senior Member
Location
Jacksonville, FL
Occupation
Electrical Instructor
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?
 
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
 
Last edited:
infinity said:
Do you have a box fill calculation that shows the box being overfilled?
Click to expand...
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 said:
I just googled it and Cantex box is 48 cu. in

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

View attachment 2562909
Click to expand...
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.
 
Rick 0920 said:
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.
Click to expand...
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
 
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.
 
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.
 
Rick 0920 said:
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.
Click to expand...
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.
 
infinity said:
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.
Click to expand...
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
 
wwhitney said:
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
Click to expand...
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.
 
wwhitney said:
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
Click to expand...
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.
 
infinity said:
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.
Click to expand...
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).
 
infinity said:
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.
Click to expand...
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
 
Last edited:
infinity said:
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.
Click to expand...
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.
 
Status
Not open for further replies.
Top