Wire sizes, plugs, and sub panel

[mark mcfarlane]

Blue items below are edits based on initial feedback.

I'm about to call in an electrician to wire up my shop, at least to start the wiring, I'll add more later,...

Eventual (likely) Tools:

• Split AC maybe in the future
• Sawstop, 220V, 13A
• Grizzly 0490, 220v, 18A
• Rikon 10-325, 220V, 7A
• Oneida Smart Pro, 220v, 19A
• Powermatic benchtop mortiser, 120v/8A, 220V/4A
• Dewalt 735 benchtop planer, 120V/15A
• benchtop drill press
• small compressor, 110V, 12A
• dehumidifier, 110V

I'm thinking its best to put a sub panel in the garage. I'll never be running more than one tool, the dust collector, and maybe a vac and the lights at the same time. This is a one-man garage hobby shop.

• Does 100 amps sound right? with a small split AC?
• Nema 6-20 outlets for all the 220 devices?
• What gauge wire for the 100 amp sub-panel feed (~80 feet)?
• Wire for the 20 amp 220 circuits: 12 gauge

I want to make sure the electrician does the work 'to code', Texas style.

I'm thinking three 20amp 220 circuits, one for the dust, and one multi-outlet run on each side of the shop. All in a 20-slot box. I already have at least one 110 circuit in the garage, plus lights, so the extra 4 slots would be for more overhead lighting and maybe a split AC some day.

[Ken Deckelman]

I would do 100 amp minimum since you are planning a mini-split AC system. The cost is negligible over a 60 amp setup.

[John Lanciani]

I agree, 100 amp panel with a minimum of 20 full sized slots and a main breaker. If you're going to have an electrician do the job the materials will be cheap compared to the labor so don't skimp there.

I won't go into a rant on codes, just remember that they are a minimum standard for safety and workmanship, be very leary of anyone who says that they work "up to code".

[Joe Angrisani]

I'm about to call in an electrician to wire up my shop....What gauge wire for the 60 amp sub-panel feed (~80 feet)?.....What gauge wire for the 20 amp 220 circuits?.....

Is the subpanel feed going to go surface-mount through conduit, or will it be romex through protected spaces? If romex, use 2-2-2-4 aluminum for a 100A feed.

The 20A circuits get 12 gauge wire. 20 amps is 12 gauge whether 120V or 240V. 15A=14ga, 20A=12ga, 30A=10ga and 50A=8ga.

[mark mcfarlane]

OK, lets assume I go with a 100 amp service.

There is a path from the main breaker panel to the garage, through the attic (except the first 5 feet, the breaker box is outside, on the back-left side of the house. There might be one spot where some drilling needs to happen between different isolated attic areas.

[John Lanciani]

If romex, use 2-2-2-4 aluminum for a 100A feed.

Just to clarify, #2 Al romex is only rated for 75 amps at 60 deg. C for branch circuits which would include this application [NEC 310.15(B)(16)] The 100 amp rating is only for service entrance feeders [NEC 310.15(B)(7)]

[Sam Layton]

Hi Mark,

I have a 100 amp panel in my shop, and it works out great. I would not have anything smaller. I agree with John about a large sub panel. I have a 40 full size space panel, and I think I have two spaces left over. I personally would not use any aluminum wire, not even for the feed. I ran 110 and 220, 20 amp plugs every 4 ft around the shop, along with some 220-30 amp for larger machines. Dont forget about the plugs on the ceiling... I am always moving tools around the shop in search for the perfect placement. There is always a plug to plug into.

I am also the only one that works in my shop. Numerous tools run at the same time with only one person working. In the summer, the A/C is on, the dust collector turns on when the saw runs, and then the compressor may kick in. Often times I may run back and forth between tools, so a couple tools will be on along with the above. 100 amps support everything great.

[mark mcfarlane]

Thanks Sam. I forgot about the compressor. Unfortunately the walls are already covered with wallboard. What I don't know is if they are insulated. If they aren't the wall board is coming down, which will make the electrical much easier and I'd be more willing to add more outlets. I'll only be at this (retirement) home for 3 weeks this summer and I was hoping to buy a saw and jointer and do a small project. That's why I thought I would hire out the electrical subpanel and a couple of outlets, but it is starting to look more like I need to spend my vacation prepping the garage.

I just learned that my son and nephew will be there for a week, so maybe I can put them to work hanging wallboard. My neighbors will think I'm nuts, the garage already looks like someone's kitchen, with custom built in cabinets, 4 closets,... Of course, none of the closets are big enough for a large dust collector and the 30' of kitchen counter space takes up valuable floor space at the walls,... Actually, my wife will probably think I'm nuts when I start whacking out walls and cabinets...

Romex-style wire is commonly used in this area, so that's what I suspect an electrician would recommend. I suspect aluminum is out of code as a feeder, I guess I have to research this more. (FWIW, the house currently has a 200A service)

Oh, the green and white table on the right of the garage is a Grizzly 0490X (well, someday). Where do the cars go?

[mark mcfarlane]

If I use copper for the 100 amp service, would it be Ser 3-3-3-4 awg ? It looks like they don't make NM-B in copper that can handle 100 AMPs in a subpanel configuration.

[Rollie Meyers]

If I use copper for the 100 amp service, would it be Ser 3-3-3-4 awg ? It looks like they don't make NM-B in copper that can handle 100 AMPs in a subpanel configuration.

NM & SER cables are sized from the 60 degree column of NEC table 310.16 if juristiction is on a 2008 or later edition of the NEC. (SER was added to that requirement in the 2008 edition).

[Rob Russell]

... I suspect aluminum is out of code as a feeder ... (FWIW, the house currently has a 200A service)

I don't understand why everyone has such a bugaboo about using aluminum cable to supply power to your subpanel - the service laterals (wires running from the street to your meter) are probably aluminum. There was a problem decades ago with "aluminum NM cable (aluminum "Romex")", but the problem wasn't as much with the cable as it was the devices. The terminals things like light switches and receptables need to be specifically rated for aluminum conductors. The same is true for wire nuts.

Properly sized aluminum cable is fine and will cost you less than copper, even though the aluminum will be a gauge or 2 thicker than the copper. For 100 amps, you would need 2-2-2-4 copper or 1/0-1/0-1/0-2 aluminum SER. When you use aluminum, it's a good idea to coat the ends of the bare conductors (where you strip the insulation) with an antioxidant like Oxgard.

[mark mcfarlane]

I don't understand why everyone has such a bugaboo about using aluminum cable to supply power to your subpanel -...

Rob, my (perhaps mis)understanding is that aluminum is fine for the main house feed, but since a subpanel is considered like a normal house circuit (since it comes off a breaker in the main panel), aluminum isn't allowed by NEC code in these circuits.

My current understanding is that the main issues with aluminum are corrosion and thermal expansion/contraction that can make junctions 'loose' over time. I suspect the proper connections (breaker on the main, lugs on the subpanel) with similar thermal expansion coefficients to the aluminum wire would make this a moot point.

This is all hearsay. I am not an electrician. I don't even pretend to be one on TV or in hotel rooms, I'm just regurgitating information from a failing memory. I haven't even looked into aluminum wiring since I bought an old house several decades ago that was built in the 50s and we had some inspection issues (Texas) with the in-wall aluminum wiring.

[Rob Russell]

... but since a subpanel is considered like a normal house circuit (since it comes off a breaker in the main panel), aluminum isn't allowed by NEC code in these circuits.

There nothing that I'm aware of in the NEC that prohibits the use of aluminum to feed a panelboard.

I'm not a licensed electrician either, just an experienced DIYer.

[Mike Henderson]

I had a problem with aluminum wire from the meter to the panel. The connection between the aluminum wire and the main breaker developed a (relatively) high resistance connection. The connection generated heat (because of the resistance) and the main breaker eventually tripped from the heat. Rather than just clean the connection, I decided to put copper in. The distance was small so the cost wasn't too bad and I didn't have to worry about having the same problem again.

I've heard that things are better now with aluminum wire but if the run is small, I'd put in copper for peace of mind.

Mike

[Chris Padilla]

Silver 62.1
Copper 58.5
Gold 44.2
Aluminum 36.9

These are the conductivities of 4 common metals in 10^6 Siemens/meter.

I think I'll do my shop in silver.

Copper is almost 60% more conductive than aluminum but how much cheaper is aluminum over copper?