Critique my plan for 100 amp sub feeders.

[iwirehouses]

Im about to run the feeders to a 100 amp sub panel in a detached garage. I already roughed in the garage and got it inspected. The next inspection will be for the finish and feeders. This is my plan...

Coming out of the main 200 amp panel, I will run #2 ser to the opposite corner of the house, where the underground run will begin. Before I go outside, the ser will enter a 16" junction box (8x the largest conduit 2") either between the floor joists or on the wall. I will crimp the SER conductors to single #2 conductors then wrap them with rubber and then tape. The single conductors will exit the 16" j-box in 2" PVC with a short stub through the wall, straight into a LB outside, straight into an expansion fitting and the ground. 90 over,get to the garage, 90 up, expansion fitting, and an LB maybe 3 feet off the ground straight into the back of the flush mounted panel.

Critique? any ideas or comments? This is your chance to complain about how other people do stuff

I can't think of a way to do this without a splice. I've never worked with a 16" junction box before, nor have I ever spliced #2. Should I just put in a disconnect instead of a junction box? My 40 hour weeks consist of roughing 2 residential houses, so I figured I'd run it by the experts first. Thanks!

 

[frizbeedog]

I would have no problem with a junction box for the wiring method transition. If a pipe run all the way is out of the question then it seems like a J box is what it's gonna take. Having said that, I always try to find a way to place the box somewhere inside to minimize the clutter on the outside. One LB through the wall is cleaner looking than a big J box. Hopefully a basement or a crawl space.

 

[gndrod]

SER transition

SER transition

You may eliminate the discomfort of doing SER splicebox work inside with a disconnect on the outside that may be cheaper with less install time and no LB. Just a thought without being there I might be out to lunch. rbj

 

[suemarkp]

Why expansion fittings for 3' of exposed conduit? What is the length of the buried conduit -- you could need an expansion fitting there, but the earth deltaT is way less than the air.

Why not run 1.5" FMC in the house and then just pull individual THWN all the way? You could use a smaller J box or just an oversized LB to make the bend (and a 2" is probably plenty large enough for #2 wire that isn't spliced).

 

[benaround]

Don't forget you need a disconnecting means ( or main cb in panel ) at the

detached building and a GES also.

 

[mistermudd]

Not really suppose to use resi cheat table for any thing but the main service. #2 alum should really be on a 90 amp breaker. Some inspectors call it some don't.

 

[iwirehouses]

yeap, the inspector told me to use #2 alum. i would put amain breaker in bothe the main panel and the sub panel...and the ground rod is already in Some great idea's guys, thanks

 

[frizbeedog]

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Not really suppose to use resi cheat table for any thing but the main service. #2 alum should really be on a 90 amp breaker. Some inspectors call it some don't.

Are you refering to 310.15 (B)(6)? 2008 code.

"Sinlge-Phase Dwelling Services and Feeders?"

 

[stickboy1375]

Why expansion fittings for 3' of exposed conduit? What is the length of the buried conduit -- you could need an expansion fitting there, but the earth deltaT is way less than the air.

I've seen conduits get pushed right through the bottom of meter cans up here where the ground freezes...

 

[stickboy1375]

Are you refering to 310.15 (B)(6)? 2008 code.

"Sinlge-Phase Dwelling Services and Feeders?"

I believe he was... You cannot use that table for what the OP is doing. 90 amp breaker for #2 AL.

 

[winnie]

My understanding is that the use of the expansion fitting in short vertical transitions to underground is _not_ for thermal expansion, but rather to provide flexibility should the soil settle differently than the structure.

If you are actually _crimping_ on to #2, then be sure to use exactly the correct crimps and crimping tool. For these sort of splices, there are also various screw down mechanical splices that you might use.

-Jon

 

[frizbeedog]

I believe he was... You cannot use that table for what the OP is doing. 90 amp breaker for #2 AL.

Then I must have missed something. Where have I gone wrong?

 

[benaround]

Feeder conductors that serve as the main power feeders. ( feed the entire dwelling)

 

[stickboy1375]

Then I must have missed something. Where have I gone wrong?

First off the OP is feeding a garage which is not a dwelling .

 

[brantmacga]

q1) is j-jox pvc or metal?

q2) are you using SER 2-2-2-4, or will it be 2-2-4? <<-- i would use the three conductor and pvc junction box. you didn't specifically say so i figured i'd go ahead and drop that in.

 

[stickboy1375]

q1) is j-jox pvc or metal?

q2) are you using SER 2-2-2-4, or will it be 2-2-4? <<-- i would use the three conductor and pvc junction box. you didn't specifically say so i figured i'd go ahead and drop that in.

Why would you run a three conductor? Just want your opinion.

 

[brantmacga]

Why would you run a three conductor? Just want your opinion.

cost savings; drive ground rod at garage.

 

[frizbeedog]

First off the OP is feeding a garage which is not a dwelling .

I just read that text preceeding the table and I am stumped. I have always installed #2 al. to out buildings with a 100 amp OCPD and have never once been called ont this. From what I think you are saying, I've been wrong all this time and every inspector that has approved these installations is also wrong.

That disturbs me..... :-?

 

[stickboy1375]

cost savings; drive ground rod at garage.

You need a ground rod at the building no matter what.

 

[iwirehouses]

i will be using 2-2-2-4 in addition to the ground rod, so I'm looking good. I plan on using a pvc jbox. I'll probably have to hole saw the knockouts, right?