Another outbuilding service cable sizing/type question.

[gentlemanfarmer]

Hi all.
Based on my google searches, I feel like this question has been asked 100 times but I still can't seem to find a straight answer based on my situation. My former electrician who installed part of this setup has recently moved as well so I don't have a local contact right now I can trust for an answer or even to just hire for this.

I have a new garage/wood shop that is nearing completion and am going to be installing a 100-amp panel in that building. It is about 50 ft from my the main house and I have a 2" conduit(underground) installed from the main panel that comes up through the concrete slab in a utility room in the shop directly beneath where the panel will be installed.

My former electrician installed a feed-through meter a few years ago when we upgraded the panel in the main house in anticipation of this new building. What wire would you guys recommend for this?

I don't have a problem using aluminum wire and I know you are not suppose to run SER Cable in an underground conduit and I don't really want to scale back to 90A either to use MHF cable. My plan was to have the original electrician run the service cable and ground that panel and I would take care of everything downstream from the breakers but since he's moved, I'm thinking I'll just pull the wire myself. Everything WILL be inspected before closing the walls up and then again when everything is 100% so I don't want to invest hundreds in wire and have to pull it out later.

Speaking of grounding, the concrete sub also brought a section of rebar for grounding up through the frost walls that that terminates a few inches above the slab inside a wall near the panel location. What type and gauge of wire do I need to ground the new panel to that rebar? It is probably about 10-15ft or so from the panel. If I ground there, do I need to run a ground back to the main panel as well?

Thanks,
B

 

[dcg9381]

> I don't really want to scale back to 90A either to use MHF cable.

I think the price point is at 90A and MHF. You can certainly do 100A, but it's a nominal change and you'll have to determine if it's worth your budget for the additional costs of copper or AL wire.

How big is your shop and what are you running in it?

I'll let someone else address the building ground question on your subpanel.

 

[gentlemanfarmer]

Hi, thanks for the quick reply. The overall building dimension is 22' x 58' and includes a small bathroom and kitchenette as well. There are 3x 240/20-amp circuits and 3x 120/20amp circuits for tools. A dedicated 240/20a for dust collection, a dedicated 240/20a for the a/c, a dedicated 240/30a for my welder. A few dedicated 120s for the beer fridge, bathroom, etc. and a couple of lighting circuits. I'm guessing I have about 28 circuits spoken for on a 32-circuit panel.


For the amount of money this building is costing, a few hundred more for that extra 10-amps is probably not a deal-breaker but the worst-case scenario is probably AC & DC and 1-2 20-amp tools running at a time, plus the various lighting/fridge, etc. MAYBE my air compressor decides to kick on at the same time? Assuming 15-amps on those 20s, your probably looking at 15a AC + 15a Dust collection + 2(15amp tools) + 5 more for lighting, frige, wifi, etc. Probably 75-80ish worst case scenario without the air compressor firing up.

 

[alfredeneuman]

I have a new garage/wood shop that is nearing completion and am going to be installing a 100-amp panel in that building. It is about 50 ft from my the main house and I have a 2" conduit(underground) installed from the main panel

Use (3 individual) #1 XHHW or THWN Aluminum and a green insulated #6 al or #8 cu for the ground

 

[gentlemanfarmer]

Use (3 individual) #1 XHHW or THWN Aluminum and a green insulated #6 al or #8 cu for the ground