Few sub panel questions

[GNX423]

Good day all, I have been reading a lot on here on the subject and have a few questions that I hope you could help me with.

I am installing a sub panel in my garage. Length of the run is 125ft underground, and 50ft through the house basement to the panel (175 overall). I will be running 2” conduit underground, and using 2-2-2-4 aluminum to feed.

I really only need about 70amps or so. Will be running a lift, 3hp compressor, general lighting and occasionally a small welder (160A tig). Not much at one time.

If I were to use MHF cable, will I need to transition to another cable type indoors? (Un-finished basement 50ft). SER maybe?

What size breakers do you recommend in the main and sub panels? Any issue connecting a #2 in the main box breaker?

Thank you, Michael

 

[tyme2par4]

You can run MHF inside, but it MUST be in conduit. So if you can run the conduit from entry to the panel without much problem, then don't transition.
If running conduit in the basement would be difficult, then you can transition to SER in a junction box.

A 70A breaker in the main panel should work just fine. I believe a 70A breaker can handle #2, but you should double check (wire size will be listed on the side of the breaker).

You'll need a neutral lug kit for both the ground and neutral bars: https://www.homedepot.com/p/Siemens-4-2-0-Neutral-Lug-Kit-For-Load-Centers-ECLK2/202315436
(some ground bars may handle #4, but not all will.)

 

[ard]

175ft AL #2 in conduit at 70A gives you exactly 3% voltage drop

FWIW.

 

[p_mori7]

Off topic...

A: a GNX

Q: If Darth Vader were to own & drive a car, what would it be ?

 

[GNX423]

You can run MHF inside, but it MUST be in conduit. So if you can run the conduit from entry to the panel without much problem, then don't transition.
If running conduit in the basement would be difficult, then you can transition to SER in a junction box.

A 70A breaker in the main panel should work just fine. I believe a 70A breaker can handle #2, but you should double check (wire size will be listed on the side of the breaker).

You'll need a neutral lug kit for both the ground and neutral bars: https://www.homedepot.com/p/Siemens-4-2-0-Neutral-Lug-Kit-For-Load-Centers-ECLK2/202315436
(some ground bars may handle #4, but not all will.)

Thank you Tyme, conduit would be a pain as I would need to run down the length and then across, so will get SER for the basement run, and tie into a junction box on the way out of the basement.

Mike

 

[GNX423]

Off topic...

A: a GNX

Q: If Darth Vader were to own & drive a car, what would it be ?

Yes sir!

 

[theoldwizard1]

... tie into a junction box on the way out of the basement.

Get a BIG junction box !

 

[mm08822]

You can also use 2-2-4-6 AL MHF. Running a reduced neutral is no problem.
You won’t need lug kits to terminate these sizes.

Using a 70A cb in the main panel should take ~#8 – 2/0 conductors.

The subpanel main cb can be any size. Consider using a 100A main breaker panel with 24-30 spaces. Readily available.

If the conduit run has few bends, you could even use 1.5”.

What is the difficulty in running conduit in the basement? Eliminating the j-box is preferred long-term and it is cheaper – no box or split-bolt connectors/tape to buy.

 

[75gmck25]

I just went through this type of project, and there are a few points I learned.

- Size of the junction box for large gauge wiring is determined by the size of the conduit connected to it. 2" conduit requires a 12"x 12" junction box. They stock them at HD and other places.

- To connect the SER to the MHF you will need the right connectors. I bought these from Amazon and they worked very well (but they are not cheap). https://www.amazon.com/gp/product/B00UKG8DNU/?tag=atomicindus08-20

- Breakers larger than 60 amps are much more expensive. I used a 60 amp breaker in the main panel, although my sub-panel main is rated for 100 amps. I can always upgrade later if I find it is needed.

- You can buy the panel lugs for larger cable at HD in packages of 2, and add them to your ground and neutral bars.

- 2" conduit is flared on one end to allow the next piece of conduit to slide in.
When you run the conduit, try to keep the joint direction the same for each piece. The 2-2-2-4 pulls through the joints easier if you pull from the 2" conduit side into the large connector.
I used a metal fish tape with foam wire pulling lubricant, and then pulled the 2-2-2-4 and another pull string through at the same time.

- I ran a 2nd smaller conduit in the trench, and plan to use it for Coax and Cat5 cables.


Bruce

 

[GNX423]

Thank you all, a wealth of knowledge here!

Conduit through the basement would be tough because of the board heating and other pipes on the floor joists.

12"x12" junction box it is.

I appreciate the experience share and help.

Mike