Advice for running electrical to detached workshop

2356 Views 24 Replies 9 Participants Last post by clawlan, Feb 12, 2016

clawlan

Discussion Starter · Feb 11, 2016

I have a decent sized detached shed that I am turning into a hobbyist grade woodworking workshop. The shed currently has one buried line going to it; I think 14/2 on a 15 or 20amp breaker. I just recently moved into the home so I am not sure yet if that breaker is dedicated to only the shed or not. Regardless, I know i am going to need more juice running to it, and if I'm going to run wire, might as well future-proof it.

It currently has no real lighting so I recently picked up several 4ft fluorescent shop lights (2 tubes each), 6 of which I plan to hang. Each tube is 32 watts, for a total of 384 watts. As far as power tools, I plan to have all the basic stuff, with a table saw likely being the biggest draw (still 110v though).

Since my knowledge of electrical is fairly basic, I'm not sure how much load I should plan for, if it makes more sense to run several small gauge wires or 1 or two larger gauges, etc. I do understand, of course, the basic principle that the breaker has to be matched to the wire load rating.

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surfing_santa

· #2 · Feb 11, 2016

I would go with one or two ed to large guage wire as most times in a shop you are only using one or two tools at once, however those tools use large currents especially large instantaneous currents that can easily trip breakers that are rated for your power load. However you may want to put things that kick on automatically like air compressors on a dedicated line to help avoid massive surges.

clawlan

Discussion Starter · #3 · Feb 11, 2016

What do you mean by "one or two ed to large guage wire"?

GottaFixIt

· #4 · Feb 11, 2016

That's a lot of light! How big is your shed?

There's a couple of good options.

One would be to install a sub panel and run either 8, 10 or 12 gauge with 2 x 120V legs. This would give the option of 240VAC outlets (like for your table saw). If you do this, you'll probably want to bury conduit and use THWN wire. You'll have breakers in the shed and can branch into several circuits.

Another would be one run of 12/3 and one of 12/2 giving you the ability to install a 240V outlet and a run of 120V outlets & lights. You could use conduit or underground feeder wire (though you probably need to trench deeper without conduit).

If you don't think you need a 240VAC outlet (which I think would be a mistake), then you could run 1 or 2 12/2s.

Option 1 would be the most versatile, but most expensive.

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clawlan

Discussion Starter · #5 · Feb 11, 2016

Nick DIY said:
That's a lot of light! How big is your shed?

There's a couple of good options.

One would be to install a sub panel and run either 8, 10 or 12 gauge with 2 x 120V legs. This would give the option of 240VAC outlets (like for your table saw). If you do this, you'll probably want to bury conduit and use THWN wire. You'll have breakers in the shed and can branch into several circuits.

Another would be one run of 12/3 and one of 12/2 giving you the ability to install a 240V outlet and a run of 120V outlets & lights. You could use conduit or underground feeder wire (though you probably need to trench deeper without conduit).

If you don't think you need a 240VAC outlet (which I think would be a mistake), then you could run 1 or 2 12/2s.

Option 1 would be the most versatile, but most expensive.

Maybe I don't need so much light? Can probably get away with 4 of those. I just got a bunch of them for dirt cheap on craigslist so I figured i put them to good use, haha.

Ah, duh, didn't even think about having a subpanel in the shed, that make so much more sense. Forgive my lack of knowledge on wire, but what do you mean by "2 x 120V legs"? I know that in order to have a 240v circuit, you need two 120v wires, but do legs mean 2 separate cables or a single cable with more bundled wires? (I've been watching a bunch of youtube vids trying to learn about wiring and terminology...)

rjniles

· #6 · Feb 11, 2016

You are only allowed to have 1 circuit to a detached building. That 1 circuit can be:
A single 15 or 20 amp circuit. Or
A MWBC which will give you effectively 2 15 or 20 amp circuits. Or
A feed to a subpanel consisting of 4 wires, 2 hots, a neutral and a ground.

The subpanel can be any any capacity you require and can support multiple circuits in the detached building.

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clawlan

Discussion Starter · #7 · Feb 11, 2016

rjniles said:
You are only allowed to have 1 circuit to a detached building. That 1 circuit can be:
A single 15 or 20 amp circuit. Or
A MWBC which will give you effectively 2 15 or 20 amp circuits. Or
A feed to a subpanel consisting of 4 wires, 2 hots, a neutral and a ground.

The subpanel can be any any capacity you require and can support multiple circuits in the detached building.

Thanks for the great info. I am thinking I will go with option 3. Does that mean the feeder can be on a circuit greater than 20 amps? And just to confirm, x/3 (12/3, 8/3, etc) wire would be the aforementioned 4 wire feed?

Oso954

· #8 · Feb 11, 2016

Deleted

rjniles

· #9 · Feb 11, 2016

clawlan said:
Thanks for the great info. I am thinking I will go with option 3. Does that mean the feeder can be on a circuit greater than 20 amps? And just to confirm, x/3 (12/3, 8/3, etc) wire would be the aforementioned 4 wire feed?

The feeder must be a dedicated circuit from the main (or subpanel) in the house to the subpanel in the detached building. It can be any size you need, 30,40, 60, 100 amps or more. The wire used as the feeder must be sized the the capacity.

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clawlan

Discussion Starter · #10 · Feb 11, 2016

Im going to have to dig up the area where the wire leave the house to see if there is a conduit running the entire length or just to the ground. I can't tell if the wire is THWN but even if it isn't i wouldn't trust that the previous owners used conduit...

rjniles

· #11 · Feb 11, 2016

clawlan said:
Thanks for the great info. I am thinking I will go with option 3. Does that mean the feeder can be on a circuit greater than 20 amps? And just to confirm, x/3 (12/3, 8/3, etc) wire would be the aforementioned 4 wire feed?

If you feed with cable, it would be x/3 configuration, 3 wires plus ground. Better to use conduit and individual THWN wires

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mpoulton

· #12 · Feb 11, 2016 (Edited)

If I were you and I were wiring this shop for future use of unknown additional equipment, I'd install a subpanel with a 100A feeder. That's what I did in my garage. Here's why:

First, it makes very little sense to go to the trouble of running power to a shop if you're not going to install a subpanel. You'd be limited to two 20A 120V circuits at most (that's a single 20A MWBC), but you still have to do all the work of trenching, installing conduit, pulling wire, adding a breaker, wiring the shop, etc. Using a subpanel is hardly much additional work or expense. Maybe an extra hour and $100. It gives you much more flexibility, and you can run as much power as you'll ever need in your shop.

Now, if you're going to install a subpanel, why run anything less than a 100A feeder? Sure, you might not think you'll need anywhere near that much power, but you don't know what you may add later. Welder? Large compressor? If you already have conduit and a subpanel in place, it's not much more expensive to use #1 aluminum and a 100A breaker. Then you'll never have to worry about it later on.

While you're at it, lay at least one extra conduit. It's cheap and easy to drop a spare 3/4" PVC conduit in the trench with your 1-1/2". If you ever want to run cable, phone, network, security cameras, or whatever else through it, it will be there for you.

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clawlan

Discussion Starter · #13 · Feb 11, 2016

great, thanks for all the help. Is there a cheaper place to buy wire than at a big box hardware store?

rjniles

· #14 · Feb 11, 2016

I find that cut wire is cheaper at my local electrical supply. But know exactly what you want if you go there. They suffer fools poorly.

Arrow3030

· #15 · Feb 11, 2016

Not sure if this has been mentioned.
All loads in the detached need to be disconnected with no more than 6 switches.
Sometimes getting a main lug panel isn't as smart as getting a main breaker panel. The main breaker disconnects all loads with one "switch".

Reactions: 1

Plumbvoltage

· #16 · Feb 12, 2016

When I did my garage, I installed a 12 space 100 amp breaker panel and fed it with 3-6ga thwn 2hots,1 neutral and 1-10ga ground in 1 1/4" conduit fed from my main panel with a 60amp breaker and ground rods of course.

60 amps is probably more than you'll ever need unless your running a lot and all at once.

clawlan

Discussion Starter · #17 · Feb 12, 2016

Alright, I think this is my plan based on everyone feedback:

Run a single, 4-wire, large gauge (2ga?) from dedicated circuit in house to a main panel in workshop via conduit.
Drop in 2nd conduit with Cat6 for networking and future low voltage expansion.
Add several circuits of varying sizes for lights, receptacles,tools, etc.

clawlan

Discussion Starter · #18 · Feb 12, 2016

Should the main breaker in the workshop be a gfci?

rjniles

· #19 · Feb 12, 2016 (Edited)

clawlan said:
Should the main breaker in the workshop be a gfci?

No, use GFCI breakers or receptacles on the individual circuits. Receptacles are far cheaper.

What amperage are you planning on feeding the circuit (from the breaker in the house)? Do you want to use AL or CU conductors? AL is 1/3 the price.

#4 AL XHHW will give you 60 amps. Price about 20 cents a foot.

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clawlan

Discussion Starter · #20 · Feb 12, 2016

rjniles said:
No, use GFCI breakers or receptacles on the individual circuits. Receptacles are far cheaper.

What amperage are you planning on feeding the circuit (from the breaker in the house)? Do you want to use AL or CU conductors? AL is 1/3 the price.

#4 AL XHHW will give you 60 amps. Price about 20 cents a foot.

I honestly don't know the difference (beyond Aluminum vs Copper) of the two, but I definitely lean towards cheaper (to google I go...). And 20 cents is way cheaper than what the big box sells at.

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