Simple box fill calculation verification

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Mustwin351

Senior Member
Location
Texas
Just wanted to make sure I am correct in my calculation.

4 square box at 2 1/8" deep equals 30.3 cubic inches....will have an industrial raised cover i'm guessing that does not increase my box volume?

inside of the box will have:
three #6 conductors = 15 in
one #10 conductor = 2.5 in
one 30 amp receptacle = two volume allowances at 5 in each or 10 in

for a total of 27.5 cubic inches.

is that correct?

no splices, loops, or clamps in box.
 
Dennis Alwon

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Mustwin351 said:
The #10 is the egc. It is a 30amp circuit with the ccc increased due to more than 3 ccc in a raceway
Click to expand...
Yeah I notice that after I posted.

I've seen so many people take a 4x4x2 1/8 and just multiply those figures. The calculation in the book measures the interior of the box, which is correct, not the exterior. You did good.
 
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Mustwin351

Senior Member
Location
Texas
thank you! I appreciate the verification...while completing the installation I was a little nervous as it was a very tight fit inside the box! I have considered changing the box out to a 4 11/16 square box but looks like there is no need.
 
Dennis Alwon

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Mustwin351 said:
thank you! I appreciate the verification...while completing the installation I was a little nervous as it was a very tight fit inside the box! I have considered changing the box out to a 4 11/16 square box but looks like there is no need.
Click to expand...
If

it bothers you just put an extension ring on it but as you said there is no need
 
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