Junction Box Sizing

[bbs]

I'm planning to use a junction box to splice a 4-4-4-4 aluminum cable to a 6/3 +gnd NM copper cable. I'd like to confirm (or correct) my understanding of how to calculate the jbox size based on table 314.28(A). The cables will enter/exit the jbox on adjacent sides of the box. The aluminum cable will be in PVC conduit. The 6/3 NM cable will be secured in a clamp connector, but will not be in conduit. Based on one conduit size calculator (https://www.southwire.com/calculator-conduit), the minimum size conduit for 4-4-4-4 aluminum cable would be 1.25". So the jbox would need to have a minimum width of 6 x 1.25" = 7.25". I think an 8"x8"x4" jbox would meet code for this application. Can someone please confirm or correct my understanding?

 

[Strathead]

Assuming your conduit fill math is correct, I believe it is from memory, you are correct, but remember, the entering and exiting cable must be a minimum of 7.25 inches apart also.

 

[Krusscher]

didn't this question already get closed by a moderator once?

 

[bbs]

Thanks. I missed the "entering and exiting cable 7.25 inches apart" piece. That would dictate a jbox at least 10.7" square, assuming the cable entrance and exit were in the middle of the adjacent walls. In my situation (45 cable feet between the jboxes), I think it will be less cost, and maybe simpler, to go with 6/3 copper for the whole run, which would allow me to use a 6"x6"x4" jbox.

 

[bbs]

Regarding closing this question, my previous post asked for some opinions about cabling and splicing, which I understand isn't allowed in this forum. This post just requested confirmation of my understanding of how to calculate the junction box size given the #4 and #6 cables to be spliced.