Building a machine shop behind the house? How to wire it?

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  #1  
Old 04-02-07, 02:13 PM
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Building a machine shop behind the house? How to wire it?

I have been searching all over the web trying to find some information about getting power to my shed. The shed will be quite close to the house, like 5 feet from the well (although in the opposite corner of the breaker box, if that matters).

I plan on having a 220V CNC mill running most of the time Im in there, with the ability to have other machines such as a 110v band saw, a 220v welder, lights, a computer (for research / calculations, and to run the Mill), a drill press, a bench grinder, a small A/C window unit, and possibly even a small radio, all at nearly the same time. I obviously dont know the exact power requirements, but I

Does anyone know of any websites where I can read up on things specifically regarding routing power to external buildings being added on to the main houshold? Would it be legal for me to do most or at least some of the wiring work myself (just lying the wiring, digging the trenches, etc, but obviously not hooking it up)? Could somebody give me a rough estimate ($200? $500? $1000? $3000? $5000? $10,000?) on about how much this would cost to have professionally done, or to do it myself if possible?

I live in Oklahoma if that is a concern.

Thank you.
 
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  #2  
Old 04-02-07, 02:28 PM
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> 220V CNC mill, 220v welder

We'll need to know the power requirements of these machines to make a reasonable guess; watts, amps, or horsepower is okay. If you already have the welder picked out, post the make/model. Also, the square footage of the building plus number of tools running at the same time.

> Does anyone know of any websites where I can read up on things
> specifically regarding routing power to external buildings being added on to
> the main houshold?

There aren't many websites, but many of the electrical how-to books at the home centers have chapters on subpanels to outbuildings. Your situation is a bit more complicated because of the mill and the welder. These are very high draw tools which are not typical on a residential service so special consideration needs to be made.

> Would it be legal for me to do most or at least some of the wiring work

Most of the time yes. If you want an electrician to do the hookup, you must meet with him before you start the project so you can decide on the split of the work. Also, he can't legally hook up anything you may have done incorrectly so you'll need his approval from the start. You'll also need to get in writing which work is covered under his permit/license and which is done by you.

> Could somebody give me a rough estimate

There are a few things we need to know to get an idea. First, the approximate electrical requirements of the mill, welder and any other large tools; the size of the building including heat and A/C loads; and, the size of your existing residential service (100A, 150A, 200A...) and the approximate electrical demands of the house including electric heat, A/C, elec. range, hot tub, etc.
 
  #3  
Old 04-02-07, 03:07 PM
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Thanks. The shop will likely be a 12 x 16 wooden shop. Walls will be insulated. I imagine I wouldnt need more than 500 watts of light, considering that they would be smaller ones focused where I was working, but Ill still say 1000 in case I get scared of the dark or something. Most of the time I wont have the AC window unit on except on the hottest days or days without much wind. The CNC mill has a 2HP motor, so around 1500ish Watts, and then I guess round it up to maybe 2500 or so including the 4 stepper motors. Then the 1/2 HP drill press, so another <500 watts (just rounding up). The welder uses about 20 amps or less since I mostly only use it for light duty (use a torch for major things), which is about 4400 watts. The small AC unit I would get would use maybe 5 amps (550 watts). The band saw uses 1 HP, so lets say 800 watts. The bench grinder Id get would surely be 1 amp or less (110 watts max).

No telephone, internet, or plumbing would be out there. No heating other than a little propane heater (which would be more than enough heat anyways), and any cooling would be obviously done by the small window-unit.

This would be a worse-case scenario in that obviously I couldnt run everything all the time and will always be energy-concious, but I dont want to try to turn something on and everything shuts off or something.

This is mostly just to get all that stuff out of the garage and into its own complete workspace so I can work comfortably. But it is definately not anything fancy, and will be for the most part just to get the job done.

*edit*

Oh and the compressors I am looking at to replace my current 25Gal range up to 7 HP peak (likely during startup) so add in like 4500 watts to cover that. But I might go with something smaller (maybe).

So:

Mill: 2500
Drill: 500
Bench Grinder: 110
Compressor: 4500
Welder: 5000
Band Saw: 800 watts
Lights: 1000 watts

Then lets say like another 5000 for additional or upgraded machines / appliances / tools.

Rounding that up again that turns out to be almost 20Kw. Realistically I could see myself doing MAYBE 10Kw at a time, like if the Mill is going, the compressor is running, and I have some other tools / lights / amenities going (radio / AC). Maybe nearly 15Kw if I have those things on, plus the welder (which generally is only used for tack welding sheet metal, but you never know), plus another person in there working with me.

But I am just trying to give myself plenty of room. Like protection, it is better to have it and not need it, than need it and not have it.
 

Last edited by JMcDonald; 04-02-07 at 03:53 PM.
  #4  
Old 04-02-07, 03:46 PM
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Okay, that doesn't sound too bad. You could probably get by just fine with a 60A subpanel feeder to the workshop. Assuming you have enough capacity in the main house panel, this should be a fairly straightforward job.

I would install a 100A panel in the shed with at least 20 spaces so that each tool can have its own circuit. The panel can be fed with copper #6/3 UF-B underground cable from a 60A DP breaker in the main panel. Assuming no complications with the house main panel or service, you're probably looking at somewhere between $1,000 and $1,500 for an electrician to get power out to the shed. Although that depends a lot on the labor rate in your area and the feet of cable between the main and the subpanel. You can probably negotiate to do some of the grunt work too.

Are you looking to have a pro wire up the tools also or do you plan on doing those yourself?
 
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Old 04-02-07, 03:52 PM
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To add:

With the compressor, I think it would be a good idea to upsize to at least a 100A subpanel feeder. This could be enough to overload your main house service which may need to be upgraded. I think my best advice is to get three estimates from electrical contractors. Your needs are complicated enough that someone should really see it onsite to get a feel for what you need.

If your electrical need in the shed is large enough, it may make sense to split your service at the meter and bypass the house panel entirely. This type of job should be evaluated and done by a professional, but may be overall cheaper because it would avoid an upgrade of the house panel. The only way to know if you need this is to do a demand load calculation of the existing house and of the proposed new building.
 
  #6  
Old 04-02-07, 04:43 PM
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Wow thanks alot! Extremely helpful!

By wiring up the tools, do you mean doing the internal wiring of the building and placing / wiring the outlets myself? If so, then yes I will do that as long as it will be legal. I wouldnt have a problem with most of this stuff except for the legality issues, I think. All the tools themselves, however, do actually use plugs that can be removed (not like Id be moving a 700lb mill around much though, hah). I also budgeted about $2000 for it so hopefully I wont have any problems.

Ive run lots of stuff in the garage with two people (welder, compressor, ~2000 watts of light, power tools, etc, which could have easily been close to 8k watts, so I dont think I should have too much trouble with it).
 
  #7  
Old 04-02-07, 08:16 PM
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If you do the job yourself, you're probably looking at somewhere in the ballpark of $500-1000 in materials. But there are a lot of variables involved in this, so it's hard to really say with any accuracy without actually sitting down and measuring cables and having a set design to go off.

In my area, you must be a licensed electrician OR the homeowner to do electrical work on your home. I believe most areas are the same way. Either way, make sure to pull a permit and get everything inspected, the inspector will make sure you don't burn your house down

One option you have is to get a professional electrician to install the panel and the feeder cable. He/she'd be used to running conduit and pulling cable, and will know how to do the calcs, connect the new ground rod and properly treat the neutral, etc. And you could DIY the "easy stuff" from there!
 
  #8  
Old 04-02-07, 09:51 PM
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Thanks! Yeah I just wanted to find out how reasonably and how likely it would be for me to legally to some or most of the work to reduce cost. I also wanted to find out about how much it would cost (within a wide range, like I mentioned). Both of those questions were answered! Thanks alot guys!

A plasma cutter would be nice also.. but at 8-9 Kw it might be a bit much for a single machine, heh.
 
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