# Shop electrical second opinion (Subpanel wiring)



## Jesse Blair (Oct 9, 2016)

I have just installed a new building to use as a woodshop, separate from the house, and I'm about to run power to it and wire it all up. I have a game plan, but I wanted to run it by any people here who may be electricians, or have knowledge on such things. I also know local codes dictate many things, but just for a general opinion I'll ask anyway. I'm planning to run a 60A breaker from my 200A service panel to a sub-panel in the shop. I have ample room on the main panel to do this. I plan to run #6 THHN/THWN in buried conduit out to the building, to another 60A breaker in the panel. According to what I've read, the wire I'll be using is rated for 65A, which should be just fine, especially considering I'll never approach 60A all at once. I was wanting to use service entry cable rated for burial, but that is a bit more costly, and harder to work with in my situation. I'm thinking 3x 20A circuits will be fine for me. I could do 4x 15A circuits, but I'd like the little extra overhead to avoid tripping breakers if I happen to have more than 1 large draw tool running at once. All of my tools use 110V, and I don't foresee needing 220 in the future. Should be fine with 2 circuits for outlets, and one for lighting, air filtration and dust collection. Aside from that, I'll have to verify if I need 1 or 2 ground rods for the sub-panel. I'm pretty sure it's 1, but I'm not positive on that.

Does this sound reasonable? From what I understand, it should meet local code, and should be perfectly safe.


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## woodnthings (Jan 24, 2009)

*Not what I have done....*

I have several 100 AMP sub panels with their own main breaker. I have 2 separate main panels a 225 AMP and a 175 AMP from which I have run the subs.

You WILL need 220 V in your shop! So, plan on using a large enough ...100 AMP panel to run all the double pole breakers you will need for the 220 V tools. 
Run large enough supply cable, and you will only need to do this one time and you won't regret the larger size and the slightly higher expense.

Why? A true 3 HP motor will need 220 V and will not run on 110 V. Many shop tools require a 3 HP motor, table saw, shaper, jointer, drum sander, air compressor, thickness planer. I have all these and more and fill up all the slots in my 100 AMP panel which also includes about 10 110V circuits. YOU can't have too many slots.


Keep in mind that because of the sub panel main breaker you can have more total amps in breakers than the panel's main breaker, since it will trip when the rated amperage is reached ... if ever. :|


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## firehawkmph (Apr 26, 2008)

I agree with Woody. I have two 100 amp panels in my shop, two different areas in the same building. If you want all the particulars of what you should be using, post on the DIY side of the forum. There are a few electricians over there that will give you all the details. 
Mike Hawkins:smile3:


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## Alchymist (Jan 2, 2011)

You will only do this once, bump it up to #4 wire and grab a 20 circuit 100 amp main breaker panel for the sub panel, preferably a Square D QO. The ground wire can be downsized to a #6. Panel itself won't cost you much more, and the little cost premium will buy you plenty of headroom. You will eventually need it, don't underestimate. :yes:


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## Jesse Blair (Oct 9, 2016)

Well, one thing I didn't mention is that this won't be my permanent, long term shop. I will for sure go all out when I build my house and shop. This shop building is on family property, and I will likely only be using it for ~2 years, so I want to keep it simple and cheap. The only 220v tool I foresee having in those two years is a jointer. My compressor is a 110v model, and the rest of my tools are 110v.

If I do need a 220v circuit later, all I'll have to do is get a breaker, outlet and run the wires, so not a big deal to do later.


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## Alchymist (Jan 2, 2011)

Jesse Blair said:


> I have just installed a new building to use as a woodshop, separate from the house, and I'm about to run power to it and wire it all up. I have a game plan, but I wanted to run it by any people here who may be electricians, or have knowledge on such things. I also know local codes dictate many things, but just for a general opinion I'll ask anyway. I'm planning to run a 60A breaker from my 200A service panel to a sub-panel in the shop. I have ample room on the main panel to do this. I plan to run #6 THHN/THWN in buried conduit out to the building, to another 60A breaker in the panel. According to what I've read, the wire I'll be using is rated for 65A, which should be just fine, especially considering I'll never approach 60A all at once. I was wanting to use service entry cable rated for burial, but that is a bit more costly, and harder to work with in my situation. I'm thinking 3x 20A circuits will be fine for me. I could do 4x 15A circuits, but I'd like the little extra overhead to avoid tripping breakers if I happen to have more than 1 large draw tool running at once. All of my tools use 110V, and I don't foresee needing 220 in the future. Should be fine with 2 circuits for outlets, and one for lighting, air filtration and dust collection. Aside from that, I'll have to verify if I need 1 or 2 ground rods for the sub-panel. I'm pretty sure it's 1, but I'm not positive on that.
> 
> Does this sound reasonable? From what I understand, it should meet local code, and should be perfectly safe.


Were you planning to pull three wires or 4? Didn't really clik on that in your initial post, but if you were only planning on three wires for 120 volts @ 60 amps, I would suggest that you add one more wire and double your capacity. If your original intent was three wires, you could add the 4th, drop to #8 wire and a 40 amp breaker in the main panel, and still have more power available than three wires at 60 amps.

If you were planning on 4 wires and a 60 amp feed, you actually can pull 120 amps of 120 volt load. (60 amps @120v on each leg). I would still go with a 20 circuit sub, as they aren't that much bigger or expensive than the smaller ones.





Jesse Blair said:


> Well, one thing I didn't mention is that this won't be my permanent, long term shop. I will for sure go all out when I build my house and shop. This shop building is on family property, and I will likely only be using it for ~2 years, so I want to keep it simple and cheap. The only 220v tool I foresee having in those two years is a jointer. My compressor is a 110v model, and the rest of my tools are 110v.


IF you are sure you won't need much in the way of 240 volts, a 40 amp breaker on #8 wire will give you 80 amps total of 120 volt power, and you can run as many 120 volt 20 amp circuits as the box will hold. You can still add a 240 circuit if you should run into the need. (The total # of breakers can add up to more than the breaker feeding it in the main panel, or the main breaker in the sub. Be aware that if you do use a sub panel with more than six breakers, it must have a main breaker.


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## woodnthings (Jan 24, 2009)

*just a small detail ....*



Jesse Blair said:


> Well, one thing I didn't mention is that this won't be my permanent, long term shop. I will for sure go all out when I build my house and shop. This shop building is on family property, and I will likely only be using it for ~2 years, so I want to keep it simple and cheap. The only 220v tool I foresee having in those two years is a jointer. My compressor is a 110v model, and the rest of my tools are 110v.
> 
> If I do need a 220v circuit later, all I'll have to do is get a breaker, outlet and run the wires, so not a big deal to do later.


This "detail" affects the entire line of thought and all the answers. You already have the answer you need.... just add a breaker and wire a receptacle. :|


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## Steve Neul (Sep 2, 2011)

Jesse Blair said:


> I have just installed a new building to use as a woodshop, separate from the house, and I'm about to run power to it and wire it all up. I have a game plan, but I wanted to run it by any people here who may be electricians, or have knowledge on such things. I also know local codes dictate many things, but just for a general opinion I'll ask anyway. I'm planning to run a 60A breaker from my 200A service panel to a sub-panel in the shop. I have ample room on the main panel to do this. I plan to run #6 THHN/THWN in buried conduit out to the building, to another 60A breaker in the panel. According to what I've read, the wire I'll be using is rated for 65A, which should be just fine, especially considering I'll never approach 60A all at once. I was wanting to use service entry cable rated for burial, but that is a bit more costly, and harder to work with in my situation. I'm thinking 3x 20A circuits will be fine for me. I could do 4x 15A circuits, but I'd like the little extra overhead to avoid tripping breakers if I happen to have more than 1 large draw tool running at once. All of my tools use 110V, and I don't foresee needing 220 in the future. Should be fine with 2 circuits for outlets, and one for lighting, air filtration and dust collection. Aside from that, I'll have to verify if I need 1 or 2 ground rods for the sub-panel. I'm pretty sure it's 1, but I'm not positive on that.
> 
> Does this sound reasonable? From what I understand, it should meet local code, and should be perfectly safe.


Basically it sounds like a good plan. I'm running my shop off a 50 amp breaker and I'm using industrial equipment. What is unknown is how far the sub-panel is from the main. You may need to upsize the wire a gauge if you are 100' away. 

Keep in mind wiring a sub-panel is different than a main breaker box. You wire all the neutral wires to one bar grounded to the main box and all the ground wires to the bar connected to the earth ground rod. It's kept separate so if the neutral is interrupted it doesn't feed power to the ground which would make the body of your tools hot. The neutral is considered a current carrying wire.


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## Jesse Blair (Oct 9, 2016)

Oh yeah, forgot the distance. It's roughly 50' (50' run of wire, not 50' building to building), so not a huge run. And yes Steve, I'm aware of the bonding/grounding deal with subpanels. Thanks for the reminder though.

And I was planning on pulling 4 wires (3 conductors plus a #6 ground). I may actually bump up to #4 wire, just in case I want or need more. What's another $50 now to save hassle later. The box I was eyeballing is an 8 space 100A subpanel box. I don't expect I will ever have enough circuits to fill that up. At most I would have 3 single pole 15 or 20A breakers, and _*maybe*_ a single 2 pole breaker for a 220v circuit.

Thanks for the input guys. Now I just need to trench... always fun... I have a backhoe attachment for my tractor, but I don't want an 18" wide trench if I can help it, and I don't really feel like paying the money to rent a ditch witch. Maybe I'll hand dig it with a spoon.


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## Steve Neul (Sep 2, 2011)

I made a homemade sub-soiler for my tractor to trench with. Then I cut the width of a hoe to about 3" wide to clean out what falls back in the hole. I ran a trench a hundred yards one time for a house I was going to build to run water, power for small power tools and compressed air. Where I'm at you can bury a water pipe 6" and it won't freeze in winter.


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## Jesse Blair (Oct 9, 2016)

I used to have 9" wide bucket that would be far better, but it's long gone. I may see if I can rig something up. Maybe I can cut a curved blade into some plate steel that will make a trench just wide enough to cram some conduit into. Rig it up to the backhoe attachment somehow... hmmm. I'm only trenching about 25-30', so I may be able to throw my back out and dig it by hand if I have to.


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## woodnthings (Jan 24, 2009)

*Use a ripping tooth*

https://heavyhitch.com/store/heavy-hitch-accessories/heavy-hitch-ripper/

There's a rip tooth or sub soiler for a 3 point hitch, maybe not a backhoe though. Easy enough to weld up something narrow. I'd follow it with some 1/1/2" plastic pipe for protection and maybe a pull line for a phone line or .....


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## Jesse Blair (Oct 9, 2016)

Ohhh! Wait, I think I have something similar that will work. Didn't occur to me until I saw the picture you posted. The only trouble I may run into is that everywhere within a few miles is one giant limestone slab. I'm about 3/4 of a mile from a limestone quarry/cement plant. The yard has little outcrops of rock sticking up everywhere. 18" depth may be out of the question in a few, if not all places. I'm surely not about to pull out a jackhammer to bust up rock on top of trenching...


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## TimPa (Jan 27, 2010)

Steve Neul said:


> Keep in mind wiring a sub-panel is different than a main breaker box. You wire all the neutral wires to one bar grounded to the main box .... The neutral is considered a current carrying wire.



the neutral bus in a sub panel installation in a detached building, is kept isolated from the box. the green bonding screw that attaches the bus to the panel is not installed. 


and yes, you will need the ground system, ground rods and grounding conductor. However, you need to ensure it is installed to your local code!


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## Jesse Blair (Oct 9, 2016)

Ended up going slightly overkill. Found some 2-2-2-4 mobile home feeder cable for pretty dirt cheap. It's stiff and oversized, but should still work for me. It's also rated USE-2, so should be good for direct burial, though I'll probably still run it through 1.5" PVC conduit. Got a 100A box, 8 space model and all of the accessories to hook this monster cable to the bars. Ended up deciding to go with 4 15A circuits for now, which will still leave me plenty of headroom for a future 220V circuit, or more 110's. Now the fun begins... Wiring to me is almost as bad and boring as painting a house.


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## Alchymist (Jan 2, 2011)

Jesse Blair said:


> Ended up going slightly overkill. Found some 2-2-2-4 mobile home feeder cable for pretty dirt cheap. It's stiff and oversized, but should still work for me. It's also rated USE-2, so should be good for direct burial, though I'll probably still run it through 1.5" PVC conduit. Got a 100A box, 8 space model and all of the accessories to hook this monster cable to the bars. Ended up deciding to go with 4 15A circuits for now, which will still leave me plenty of headroom for a future 220V circuit, or more 110's. Now the fun begins... Wiring to me is almost as bad and boring as painting a house.


Looks like you're almost there ....
I'd still run #12 for 20 amp 120v circuits - cost is minimal for the upgrade. There are things like circular (Skil type) saws that can easily pop a 15 amp circuit under full load. BTDT.

Just look at the ratings on these:
http://www.lowes.com/pl/Corded-circular-saws-Circular-saws-Saws-Power-tools-Tools/4294607773

https://www.google.com/search?q=ski...rome..69i57.3739j0j8&sourceid=chrome&ie=UTF-8


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## Jesse Blair (Oct 9, 2016)

Yeah, after thinking about it further, that's the smart way to go. I had originally planned that. Not sure why I changed my mind at the store and grabbed the #14 and 15 amp parts... I guess I saw the $15 difference in 100ft rolls of romex and my cheap instinct kicked in. :icon_smile:

Already wired up 4 outlets, but that's easy enough to rerun and redo. Luckily, romex is cheap and so are outlets and breakers. Stupid me!


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## Steve Neul (Sep 2, 2011)

You can always save the 14 gauge for lighting. That's really what it's intended for.


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## Jesse Blair (Oct 9, 2016)

Steve Neul said:


> You can always save the 14 gauge for lighting. That's really what it's intended for.


Yeah, I'll find a use for it. Went back and swapped out the outlets and breakers and spent another $105... ugh. I guess it'll be worth it not having to walk to the panel to reset the breaker every time a tool bogs down cutting through hard woods... :laughing:


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## Jesse Blair (Oct 9, 2016)

I'm 95% there. Worked ALL day today, trenching, laying the conduit and cable, and finished up a few loose ends on the interior wiring. All I have left to do is drill a 2" hole in the sill of my house to pass the conduit through, run it up to the main panel and wire it up there. Looking forward to flipping a light switch for lights, and not using an extension cord for everything. Tomorrow there will either be power, or a fire...


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## m.n.j.chell (May 12, 2016)

Waiting to hear/see which of the options happened !!!
light or fire ???


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## Jesse Blair (Oct 9, 2016)

:icon_smile: I was feeling a bit lazy today, and burned out on doing wiring. Maybe I'll finish buttoning it all up in the next day or two. Worked on another project instead... with my extension cord...


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## Keptheart (Mar 9, 2017)

Asking politely as an electrician, how did your wire up go? There's a few things you should know about installing a sub panel. First and most important thing is that you MUST have your grounds and neutrals on separate bars and the sub-panel neutral must not be bonded to the sub-panel enclosure. My other question is how did you connect into your main panel back at the house as 2-2-2-4 is some really thick stuff and my guess was that it was a bugger to tap into a standard 2 pole 100amp breaker. I know of many ways it can be done with that cable, but they're a little complex. The only reason I'm writing this is because most wood guys are as good at electrical work as electricians are good at wood working. I would also hate to see something happen that brings an insurance inspector who flags the whole shop. Generally, with electrical work, there's so many rules and regs that the common person doesn't understand enough about to see the need to follow them, but it's nothing to play around with, as you might know what you did and how you did it, but the next guy coming along to do some electrical work there, is going to be at great risk long after you're gone. Let me know if you need some direction, I'm more than willing to guide you (or anyone here reading this) through to make it right if theres any questions.


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