wire change in junction box question

[jpcjguy]

Hi all,

I am planning the electrical to my detached garage that is about 240 feet from the house. I am running 4/0 aluminum XHHW to the garage from a 125A breaker in one of my house panels. I have twin 200A panels in my house garage.
I am going to be mounting an 18"x18"x6" junction box outside of my attached garage just opposite my twin 200A panels. The 4/0 wires are going to be run in 2 1/2" conduit. I am also running two other conduits into the box for future projects. The size of the box was given to me by my local inspector so I am good there.
Since 4/0 aluminum won't fit into my 125A breaker, I will transition to copper inside the panel using polaris connectors. I am only looking at a couple feet from the connector to the house panel. What size copper should I use and what type of wire? I am going through the back of the outside panel and into the wall and from there through a stud or two and up into the house panel. Attached is a pic of the outside location of the new junction box. The inside panels are just opposite of the meter.

Thanks!

 

[exranger06]

If you're not running conduit continuously from the junction box to the main panel, you'll need to use a jacketed cable such as SER. If you are running conduit, then you can use XHHW individual conductors.
1/0 copper SER cable is good for 125 amps.
XHHW copper can be slightly smaller at 1 AWG (good for 130 amps)

 

[pattenp]

If you're not running conduit continuously from the junction box to the main panel, you'll need to use a jacketed cable such as SER. If you are running conduit, then you can use XHHW individual conductors.
1/0 copper SER cable is good for 125 amps.
XHHW copper can be slightly smaller at 1 AWG (good for 130 amps)

#1 Cu SER is also good for 130A @ 75C and can be used as such as long as no more than 10% of the feed length is buried within thermal insulation for a max distance of 10ft. Only when SER is installed within insulation beyond those lengths is the 60C rating to be used. See NEC 338.10(B)(4) and 310.15(A)(2)Exception

 

[jpcjguy]

I am not sure what is the best avenue to take - continuing conduit or run just appropriate jacketed wire. (This is an external wall so should be interested what I find insulation wise when I take the drywall off) I will have to go through a 2x4 or 2, so I would think keeping the overall diameter of the wires the smallest would be ideal, and possibly not doing a bunch of conduit turns....

 

[jpcjguy]

So i emailed with my inspector and he said to use to the NSI connectors and then use SER cable from the outside junction box to my panel. This is through the back of the panel, into the wall, through a stud and up into the house panel.

On another note, I will be running a 1" conduit also from the junction box to under the house. This will be for a dedicated circuit for a future screened in porch. Might as well do it while the trench is open! This would be a 20A circuit for an outlet or 2, overhead lights and a ceiling fan. For now I plan to terminate the 1" conduit in a junction box in the crawlspace attached to the floor joists. I would like to run the wire while I have the wall open. What wire can I run from the panel, through the wall bay (and a stud), into the junction box and through the conduit to under the house? Can it be one wire or do a similar splice that I am doing for the detached garage wire?

 

[exranger06]

If you use UF cable, you can have one continuous run from the main panel to under the house.

 

[wyliesdiesels]

If you use UF cable, you can have one continuous run from the main panel to under the house.

good luck getting UF in sizes bigger than #6...

 

[exranger06]

good luck getting UF in sizes bigger than #6...

I was responding to OP's latest post, where he was asking about which wire to run for the 20A circuit

So i emailed with my inspector and he said to use to the NSI connectors and then use SER cable from the outside junction box to my panel. This is through the back of the panel, into the wall, through a stud and up into the house panel.

On another note, I will be running a 1" conduit also from the junction box to under the house. This will be for a dedicated circuit for a future screened in porch. Might as well do it while the trench is open! This would be a 20A circuit for an outlet or 2, overhead lights and a ceiling fan. For now I plan to terminate the 1" conduit in a junction box in the crawlspace attached to the floor joists. I would like to run the wire while I have the wall open. What wire can I run from the panel, through the wall bay (and a stud), into the junction box and through the conduit to under the house? Can it be one wire or do a similar splice that I am doing for the detached garage wire?

UF is easy to find in #12.

 

[jpcjguy]

So will UF #12 be impossible to pull in 1" conduit?

 

[Bert_]

So will UF #12 be impossible to pull in 1" conduit?

A 12-2 UF would pull pretty good in 1". Also depends on the distance of course.

You could also just splice it in the junction box. Run Romex in the house and thhn in the conduit.

 

[FarmerPete]

<--- Not an electrician. Why not just run a conduit from your electrical panel to the junction box outside? Why open the walls? That seems like a 10 minute job vs a rip drywall off and try to route conduit inside the wall job. If it's a limitation of the junction box, than just get a bigger one. I'd rather spend a few extra dollars on the box than rip my walls open.

 

[jpcjguy]

<--- Not an electrician. Why not just run a conduit from your electrical panel to the junction box outside? Why open the walls? That seems like a 10 minute job vs a rip drywall off and try to route conduit inside the wall job. If it's a limitation of the junction box, than just get a bigger one. I'd rather spend a few extra dollars on the box than rip my walls open.

My panels are on the opposite side of the wall from the meter. So I am really only opening a small section of the inside garage wall. Taking out the drywall allows me to drill through a stud or two( since I am offset a little due to the meter) to run the wire into the bay below the inside panel so I can go up into it.