electrical help

[diesel06]

need some advice on what type of wire to use for my detached garage. its a 42 by 27 morton, i have 200 amp service to the house, would like to run 90 amp to a sub panel in the shop, only running lights, outlets, air compressor, welder , would like two plugs for 220v, i heat with a woodstove. my main is in the basement towards the front of the house, plan on running the wire through the basement out through the crawl space on the new addition and then outside 20 feet into the shop. the whole run would be about 110 ft , only being outside about 20 ft.

 

[rockwithjason]

mobile home feeder cable seems to be the go to. If i remember correctly the #2 aluminum will get you 90a. It will have to be in conduit inside the building. there are guys here that do more of that kind of work than i do and they will correct me if i am wrong.

 

[pattenp]

I agree with Jason. Sounds like 2-2-2-4 MHF is a good wire for you to use. It is rated to a max of 90A. It is a direct bury cable but does have to be in conduit where inside the structure and exposed above ground. But, I suggest 2" PVC conduit from panel to panel.

 

[diesel06]

so i would need to run conduit through the basement and crawlspace?

 

[wyliesdiesels]

so i would need to run conduit through the basement and crawlspace?

Yup if u use MHF...Your other alternative is to use #2 AL SER in the house and transition to MHF in a j box either on an outside wall or get an LB to go into the wall and mount the j box in the basement close to the outside wall.

Dont forget 2 ground rods and that The neutral bar/bus in the subpanel needs to be isolated/unbonded from the ground bus bar and panel enclosure!

 

[diesel06]

could i use the same wire for 100 amp?

 

[CNGsaves]

Could i use the same wire for 100 amp?

^ ^ ^ Nope . . . . . see prior GJ threads where the Sparkies explain that particular rule limits MHF Al 2-2-2-4 as 90A when it is feeding a subpanel.

Thus, the garage can have a 100A breaker panel (ie subpanel), but the controlling breaker in house will have to be 90A. Thus, the 100A main breaker in subpanel in garage acts as single-throw shutoff.

OP if you absolutely "must" have 100A, then you'll have to use different wire.

 

[diesel06]

just curious what would the 100 amp wire be

 

[AndyCBR]

just curious what would the 100 amp wire be

#3 copper or #1 AL.

You pick the type based on the installation (crawl space, attic, underground, conduit,etc.)

 

[wyliesdiesels]

And if u go with SER and its buried in insulation for more than 10% of the length, the ampacity is gonna be limited to the 60* c rating...

 

[diesel06]

so with running it through the basement, crawl space and about 20 ft underground in conduit my best option would be 2-2-2-4?

 

[AndyCBR]

so with running it through the basement, crawl space and about 20 ft underground in conduit my best option would be 2-2-2-4?

What do you want to do?

NEC says 2-2-2-4 AL only good for 90A when used as a sub panel. If more than 10 feet is in insulation knock that down to 75A and you can breaker at 80A (one size up rule).

If that is OK then several posts above have suggested how to run it. If it were me I would use 2-2-2-4 SER AL and switch to 2-2-2-4 MHF for the underground run. YOU CAN'T RUN THE SER UNDERGROUND. If you're not in any insulation you can breaker that at 90A.

If you absolutely must have 100A then you need something else (#3 copper or #1 AL)

 

[diesel06]

how deep should i bury the wire?

 

[AndyCBR]

how deep should i bury the wire?

We still don't know where you live but most places 24" minimum for direct burial or 18" deep for wiring in conduit.

Up to you if you want to direct bury or not. There is certainly an advantage to conduit should you have a problem later (not to mention less burial depth initially). For such a short run I would put in 2" conduit and perhaps you could dig the 18" by hand/helper rather than getting a machine involved.

 

[diesel06]

sorry bout that live in pennsylvania, im just going to run 2-2-2-4 MHF in 2 inch conduit from panel to panel

 

[AndyCBR]

sorry bout that live in pennsylvania, im just going to run 2-2-2-4 MHF in 2 inch conduit from panel to panel

That will work for sure and with the distance you are talking about it shouldn't be too much of a chore. You also eliminate the splice which makes life easier.

Try to minimize the 90's and if you must make more than 2 or 3 put in an LB for an intermediate pull point.

Let us know how it works out and share some pics.

Best,
Andy

 

[diesel06]

will do, i plan to run the conduit under the garage wall into the garage and come up behind my woodstove, i dont have it all concreted yet so i wanna do it before i finish the rest, only 12 by 27 section is concreted on the one wall was like that when i bought the place

 

[diesel06]

update got the electric ran, last weekend, concrete crew is coming this week ill try to get some pictures up soon

 

[AndyCBR]

 

[wyliesdiesels]

Good job