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Discussion Starter #1
New to me acreage with 30'x40' shop (Lester building), no power currently...getting ready to run 100 amp service when ground thaws.

Shop will be used to for woodworking and automotive work. Biggest power draws currently will be Campbell Hausfeld Pro-180 mig welder, 240v 60 gallon air compressor, old-school table saw. May add plasma cutter and heater down road.

At previous house I had electrician run 240v line to garage. I pulled that breaker box from old house and plan to use in the shop.

Air Compressor: Box already set up with 20A/240v circuit breaker. Compressor will be ~30 feet from the box, by my calculations I should be able to use copper 12AWG, correct?
 

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Air Compressor: Box already set up with 20A/240v circuit breaker. Compressor will be ~30 feet from the box, by my calculations I should be able to use copper 12AWG, correct?
12 AWG should be fine at that distance (be sure to include both vertical and horizontal runs in your total length measurements.). Here's a decent calculator:

Voltage Drop Calculator

"utilizing a #12 Copper conductor will limit the voltage drop to 0.87% or less when supplying 20.0 amps for 30 feet on a 240 volt system."

 

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Maybe I missed it but what is the current draw on the compressor?
 

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Discussion Starter #4
Maybe I missed it but what is the current draw on the compressor?
Thanks RodW.

Gizmo2: not sure on current draw from compressor. The 20A/240v circuit worked in previous house.

Welder: Box already set up with 20A/240v circuit breaker. Want to put 240v outlets on east and west side of the shop. East side will be 15' from box, then will run line up wall, across truss, then back down wall to west side of shop, another 40' of wire (~55' total). Calculator calling for copper 10AWG(?). Can I run 10/3 to junction box, branch off to first outlet with pigtail, then run remainder over shop to west side? Note: Will only be using one outlet at a time.
 

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Maybe I missed it but what is the current draw on the compressor?
I maybe stupid but why do you need to know the start up and running load in amps? Just use the 20 amp breaker and #12 wire and if the breaker trips or the wire melts you go bigger or buy a new compressor! DAH!:dunno::lol:
 

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I maybe stupid but why do you need to know the start up and running load in amps? Just use the 20 amp breaker and #12 wire and if the breaker trips or the wire melts you go bigger or buy a new compressor! DAH!:dunno::lol:
Hopefully they make an equivalent to this for building wiring:

Lucas Replacement Smoke Kit
 

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Can I run 10/3 to junction box, branch off to first outlet with pigtail, then run remainder over shop to west side? Note: Will only be using one outlet at a time.
Oops, I guess you can.
 

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Go with 10AWG and don’t look back. The breaker is to protect the wiring, not the device. The breaker has to be sized correctly due to the wiring. 14AWG uses 15a on 120, 12AWG uses 20a on 120, so on and so forth.

So if you need to use 20a on 240, you can go 12AWG and still be fine as long as your run is short enough to be appropriate. 10AWG would be better and you can still legitimately use a 20a breaker. You can always go larger wire size for the breaker size, but not the other way around.

10AWG isn’t that much more expensive and allows a fudge factor and for future upgrades. :thumbup1gif:
 

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I don't think so if you want it to be NEC compliant.
No, it’s fine. He can run many outlets on the one circuit. The breaker is to protect the wiring, not the devices. If he runs more than the breaker can handle, it trips. It won’t overheat the wiring and potentially cause a fire.

There may be a limitation on how many outlets on a circuit, but he’s not going to exceed it in this case.
 

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Discussion Starter #10
I don't think so if you want it to be NEC compliant.
Country life, so no inspections needed. But safety is #1 concern...I don't want to burn down the shop.

Would I need to run a separate 240v line to other side of the shop, and have it on it's own breaker?
 

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But safety is #1 concern...I don't want to burn down the shop.



This is the reason the NEC was put in place in the first place. I would suggest getting the advice of a qualified electrician in your area. Maybe have one do the 100 amp feeder and install the breaker box. Then get his recommendation on breakers and wiring needed for the load. In todays world if it installed incorrectly the installer could be held responsible when an issue arises possibly voiding the insurance policy. I have seen electricians work with people and let them do some work. Also bear in mind the fact in your rural area you can slide by with no inspection but when it comes time to sell you may be required to get it inspected to complete the sale. It happened to my son who got somewhat lucky in that the inspector knew the electrician that he had worked for in the past, and did not find any real issues. Gotta remember certain things don't cost they pay in the long run. In doing my own electrical work I consult that same electrician with questions
 

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No, it’s fine. He can run many outlets on the one circuit. The breaker is to protect the wiring, not the devices. If he runs more than the breaker can handle, it trips. It won’t overheat the wiring and potentially cause a fire.

There may be a limitation on how many outlets on a circuit, but he’s not going to exceed it in this case.
I'm not aware of it as far as the NEC is concerned!:dunno:
 

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Discussion Starter #13
I would suggest getting the advice of a qualified electrician in your area. Maybe have one do the 100 amp feeder and install the breaker box. Then get his recommendation on breakers and wiring needed for the load.
YES! That is the plan!

Rough calculated power usage for air compressor, welder, table saw, mini-fridge, lights, hand tools, etc. estimated need total of 56 amps (if all running at same time). Allows room to add in a 5000w electric garage heater...would put me at 71 amps total usage. 100 amps should cover my current and future needs.

I plan to bury the line myself, then have electrician hook up to the house and the shop. And will certainly pick his brain on other components as well.
 

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Country life, so no inspections needed. But safety is #1 concern...I don't want to burn down the shop.

Would I need to run a separate 240v line to other side of the shop, and have it on it's own breaker?
Sorry, I was thinking of dedicated circuits. As dieselshadow pointed out, just be sure the breaker size does not exceed the conductor ampacity.
 

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Gizmo2: not sure on current draw from compressor. The 20A/240v circuit worked in previous house.
IMHO, Hire an electrician.
 

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IMHO, Hire an electrician.
Getting an electrician to do the panel sounds like a good idea since you haven't done that level of work before. If you want help with the overall design so you don't have to pay more for advice, I've had great luck in this forum: Electrical Wiring - GardenWeb
 

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Discussion Starter #17
IMHO, Hire an electrician.
Nope.

My Dad a retired carpenter. Between Dad, brother and me, there is not much we cannot do...well, we aren't the most knowledgeable on electrical...so I read, research, and ask questions.

Taught myself how to build computers, photography, photo-editing, welding, auto-body-repair, auto repair. Dad used to build houses from the ground up, and brother is a school teacher...super handy.

Part of the fun is setting up the shop...researching, planning, visioning...

I do draw the line at the electrical box. I will get in there to add a new circuit, but for the most part, it scares the hell out of me.

I've wired three basements (remodel and finish), and tend to over-engineer things (you should see the shelves I built in garage...)

"Overkill is underrated!"
 

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Daubs, At least check with a qualified electrician on ground fault requirements...AFCI, Arc Fault Circuit Interrupter... A short in a tool, a damp floor, and you're in a heap o trouble!
As a side note, I believe NEC limits the number of receptacles to 10 on a single breaker. Bob
 

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Just a couple of thoughts that I use when wiring my shop. I tend to over engineer as well but I don't get problems down the road.

Mark what breaker run each outlet is on at the outlet. Then if you do have to run a couple of hogs they can easily be on different breakers.

Breakers and wire are fairly cheap compared to your convenience. It is easier to add extra runs at the beginning than later. If your shop is like mine, it will grow. You can always stub them off for now in a box and leave the breaker off.

You may only run one or two things at a time. If you get a friend or helper in there that could more than double as you both do things at the same time. Plan the outlet groupings accordingly.

Consider switched outlets in your plan. They can be useful for some things. I put my outdoor sensor lights through light switches as sometimes I want it truly dark.

Don't forget outlets on the outside of your shop. Use GFCI. A GFCI breaker can cost as much as several GFCI outlets.

Make sure the runs are critter proof if the building isn't. I once had a rabbit eat through a plugged in fan cord. The fan stopped but the rabbit didn't. I was just lucky there wasn't a fire.

Checking with a good electrician is great advice, as well as looking at NEC yourself. Both are conservative for good reason. The electrician can also advise on any local codes. Safety should be paramount.

Think critically and ask questions. Anyone else remember the aluminium home wiring craze? Now some places require you to replace the aluminium with copper before you can sell.
 

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Daubs, At least check with a qualified electrician on ground fault requirements...AFCI, Arc Fault Circuit Interrupter... A short in a tool, a damp floor, and you're in a heap o trouble!
As a side note, I believe NEC limits the number of receptacles to 10 on a single breaker. Bob
Could you quote a section number for us wanting to know where to find it?:munch:
 
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