Detached garage sub-panel questions

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  #1  
Old 12-08-20, 04:55 PM
J
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Detached garage sub-panel questions

Hi!

I'm planning to diy wire a new sub panel in my detached garage in NJ to convert it to a music studio. I want to be prepared with my plan before I ask for a permit from the inspector, and I was wondering if I'm on the right track.

The main panel is an eaton cutler CH30JJM150N.
80' run from the main panel to the planned garage panel. I plan to use a 2 pole 60 amp breaker in the main panel. Wire is 2 hot/1 neutral 4 ga. Copper thhn/tnwn-2. Bare 6 ga. Copper ground. All in sch 80 conduit. Panel to the basement with wire in conduit hung from floor joists, exit house and trench from house to garage sub panel. Separate ground and neutral in subpanel, 2 ground rods at garage. Use a main panel with a 60 amp main breaker as a sub panel. Branch circuits are (1) 15 amp mini split circuit with outside shut off breaker for service, (1) 15 amp light circuit, 4 fixtures (1) 15amp power circuit, 6 interior outlets.

-Is this wire an acceptable choice?
-What size conduit would be good so it isn't too hard to pull the wire?
-Do I need to balance the load in the main panel? Both legs have 7 15amp circuits.
-Do all the new breakers need to be dual afci/gfci?
-I planned on having a couple exterior lights and 2 outlets. Do those need to be on a separate circuit?



 
  #2  
Old 12-08-20, 07:37 PM
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If doing conduit from main panel to garage subpanel I suggest using aluminum XHHW-2 in the sizes of #4 for the current carrying conductors and #8 for the ground for 60A service. Use a 100A main breaker panel for the sub because they are readily available.
The conduit only needs to be sch80 where subject to possible damage.
At least 1 inch conduit is needed by the NEC.
Oullets and lighting are best being separate circuits.
I would plan on the outlet circuits being afci/gfci protected.
 
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Old 12-08-20, 08:16 PM
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Thanks! Do you think it would be tough to pull the wire in 1" conduit with 3 90 deg bends over an 80' run? Should I go up to 1-1/4" or 1-1/2"?
 
  #4  
Old 12-09-20, 06:32 AM
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I did a 60A run this year with 1" pvc, about 100'. a couple of 90's, a 45, LB's at each end. But I did #6 copper. In aluminum, I would definitely go up to 1 1/4. It will need lube and a helper also. But, the hardest part is trenching; in my case, it was thru hard clay, and I rented a trencher. Even 12hp had a time with it, and took several passes to get to a 20" trench.
Also, my inspector wanted to see a couple of removable vertical stubs along the trench, to show depth.
Its also a good idea to lay warning tape a foot down. Not sure its code, but its easy and cheap. I've already had to dig to the old trench for yet another outbuilding electrical conduit lay, and the tape works!
 
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Old 12-09-20, 10:53 AM
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You got good info above.

No need to balance the panel. Residential loads are rarely out of balance and services are sized to handle it regardless. It's a bigger deal in commercial spaces.

The CAFI requirement depends what code cycle your area is on. I'd ask your inspector as it'll save some money and hassle if you don't need it on all your circuits. It's also important to understand which circuits do and don't require - and again, depends on which code you're on.

Also, if the garage is finished (walls, flooring, etc), then it's considered an interior space and doesn't necessarily require GFI. If it's still more like a garage with cement floors, GFI will be required. (And AFCI based on your code cycle).

 
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Old 12-09-20, 05:21 PM
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Thank you both! I plan on renting a trencher, I think my local equipment rental might have a 20hp. The ground isn't hard here, just some medium sized tree roots about 15' away from a tree.

it will be insulated finished garage, i lifted it 3' and put it on 3' of 8" solid block, its wood framed above. The floor will be a concrete slab on grade with rigid insulation beneath and waterproof vinyl floor. I'll ask the inspector which circuits need gfi.

How should I handle the wall penetration for the conduit on the outside above grade? Should I use an lb conduit body? Its a wood framed wall
 
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Old 12-09-20, 05:50 PM
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How should I handle the wall penetration for the conduit on the outside above grade? Should I use an lb conduit body?
Yup, an LB is a good way to get into the structure.
 
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Old 12-10-20, 02:34 PM
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All 120V receptacles in a garage need to be GFCI protected per the NEC.
 
 

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