Proper sized Junction Box for 4/0 splice

[ebasista]

I ran power to my detached garage using mobile home feeder (4/0, 4/0, 4/0, 2 XLP). Didn't realize the error in my ways. I have about 10ft of this cable hanging in my crawlspace and wall into my mains panel.

Since this cable isn't rated to be inside the home, I was going to splice it with 4/0 SER cable or similar to my main box.

I have 2.5" conduit on the outside that I'll have to put a junction box and splice the cables. What is the correct size box for this? I can't find docs on the space required for conductors this big. Any thoughts on the best way to fix the 10ft distance that's not up to code?

 

[teamextreme]

j-box sizing is based on the conduit size entering the box and the relative entry points. Need to know that info first. Is it an in/out on opposite sides, side to back, side to adjacent side?

 

[Aceman]

Mobile home feeder can be inside a structure.

 

[ebasista]

Can it be in a structure but not in conduit? That's my problem, I have the 4 twisted wires coming into my crawlspace and just hang below the joists to the main panel (about 10 feet)

 

[wyliesdiesels]

Can it be in a structure but not in conduit? That's my problem, I have the 4 twisted wires coming into my crawlspace and just hang below the joists to the main panel (about 10 feet)

No. Needs to be in conduit inside...

Aceman was just correcting what u said about MHF not being allowed inside...

 

[ebasista]

Anyone know how big a box I need to do this splice and follow code?

 

[rockwithjason]

j-box sizing is based on the conduit size entering the box and the relative entry points. Need to know that info first. Is it an in/out on opposite sides, side to back, side to adjacent side?

need this info first

 

[awdblazer]

this is going to be a junction box not a pull box so you dont need to know conduit size

 

[theoldwizard1]

Can it be in a structure but not in conduit? That's my problem, I have the 4 twisted wires coming into my crawlspace and just hang below the joists to the main panel (about 10 feet)

As stated, conduit is required inside of a structure.

My gut tells me that running conduit may be cheaper/easier than making a junction, unless there are some weird corners or no space on the load center housing for a conduit connection.

Large J-boxes can be VERY expensive ! (More than 10-15' of 1.5 - 2.0 flexible conduit and a couple of fittings)

 

[ishiboo]

I would go the conduit route if at all possible. I think you're going to need a 12x12x4 and want a 16x16x4 to make four 4/0 splices happen comfortably.

 

[Mustang51js]

Usually multiply the biggest pipe by 8. So 2.5x8=20. So a 20x20 would be plenty. There's other measurements you can do but x8 is a good rule of thumb

 

[toplessHO]

I have about a hundred ft of 6x6 and 8x8 gutter
you will need to supply a crew cover for it tho