I'm installing an underground feeder between a main service panel in a cabin and a sub-panel in a detached shop. The service will be 240V / 50A. I'm considering using 4-4-4-4 aluminum URD direct burial cable, spliced onto 6/3 NM-B cable in junction boxes at each end. The distance between the junction boxes is about 45'. I'll have a 2" conduit connected to each Jbox for the #4 aluminum cable.
1. A 6"x6"x4" jbox would meet code if all wiring is #6. With the #4 aluminum, I'm not quite sure if I'm calculating the jbox size correctly based on table 318.28(A). I think the minimum conduit size for 4 x #4 aluminum wires is 1-1/4", so one dimension for the box would be 6 x 1.25 = 7.5". If I have to use 8x8x4 jboxes, the cost of the #4 aluminum is about the same as 6/3 UF copper with 6x6x4 jboxes. Am I calculating the jbox size correctly for #4 aluminum? Any comments on #4 aluminum feeder vs. 6/3 UF?
2. I'm planning to use Polaris connectors, especially if I'm splicing #4 aluminum to #6 copper wires. Even if I use all #6 copper, I might use the Polaris connectors due to the cramped conditions I'll be working in where one jbox is located (3' crawl space). These are expensive but might be worth the cost due to ease of use. Any thoughts on my splicing options?
Thanks!
1. A 6"x6"x4" jbox would meet code if all wiring is #6. With the #4 aluminum, I'm not quite sure if I'm calculating the jbox size correctly based on table 318.28(A). I think the minimum conduit size for 4 x #4 aluminum wires is 1-1/4", so one dimension for the box would be 6 x 1.25 = 7.5". If I have to use 8x8x4 jboxes, the cost of the #4 aluminum is about the same as 6/3 UF copper with 6x6x4 jboxes. Am I calculating the jbox size correctly for #4 aluminum? Any comments on #4 aluminum feeder vs. 6/3 UF?
2. I'm planning to use Polaris connectors, especially if I'm splicing #4 aluminum to #6 copper wires. Even if I use all #6 copper, I might use the Polaris connectors due to the cramped conditions I'll be working in where one jbox is located (3' crawl space). These are expensive but might be worth the cost due to ease of use. Any thoughts on my splicing options?
Thanks!
