New guy trying to understand NEC requirements for spliced junction box sizing

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Plbnyn

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I am trying to understand the math for determining a junction box with 13" PVC conduit containing 3 300 MCM Al wires and a 4awg ground wire with a straight pull . The connectors are Allen bolt plastic covered one wire in one wire out splices. The math for a simple box makes one side 24" ? What is added for the connectors they are 2-2.5" long and 1-1.5" tall
thank you for any and all help
Andrew plbnyn Logan
 
Plbnyn said:
I am trying to understand the math for determining a junction box with 13" PVC conduit containing 3 300 MCM Al wires and a 4awg ground wire with a straight pull . The connectors are Allen bolt plastic covered one wire in one wire out splices. The math for a simple box makes one side 24" ? What is added for the connectors they are 2-2.5" long and 1-1.5" tall
thank you for any and all help
Andrew plbnyn Logan
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box length needs to be 8X diameter of largest conduit on strait pulls see 314.28 (2008 NEC)
 
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The size of the box for a 13" conduit would be pretty big......... :p ........ just kiddin.


JAP>
 
jusme123 said:
https://youtu.be/hO6DxHpdQPU

since your conduits contain 300mcm conductors , which are larger than 4/0 conductors, box size is determined differently because of the larger conductors. See 316.28(A)
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What do you mean by this? It makes no sense to me. The box size is based on the nominal conduit size. With and allowance to downsize the box IF the conductorsare smaller. Are you thinking backwards? And my 2011 code book doesn't have a section 316. anything
 
Strathead said:
What do you mean by this? It makes no sense to me. The box size is based on the nominal conduit size. With and allowance to downsize the box IF the conductorsare smaller. Are you thinking backwards? And my 2011 code book doesn't have a section 316. anything
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its supposed to read 4 awg or larger and the section is 314.28

OP stated that he had 3-300's in a conduit going strait thru box, because of the wire size, 314.28 is the appropriate code article .
 
Plbnyn said:
Ok so does that include the spice and does it matter how the box goes long up and down or side to side.
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Since you have 3 inch conduit that means for a straight pull it must be 24 inches across. No minimum width but it will have to be large enough for the 3 inch raceway entries.

If you end up with essentially a 4 x 4 x 24 inch gutter you may come close to not enough room for splices though - the splices definitely would need to be staggered in that size of a gutter, I think.
 
kwired said:
Since you have 3 inch conduit that means for a straight pull it must be 24 inches across. No minimum width but it will have to be large enough for the 3 inch raceway entries.

If you end up with essentially a 4 x 4 x 24 inch gutter you may come close to not enough room for splices though - the splices definitely would need to be staggered in that size of a gutter, I think.
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Thank you I will look up the code again and then the county to get confirmation all good info for a newbie
 
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