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Thread: Garage Shop Power Recommendations?

  1. #1
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    Garage Shop Power Recommendations?

    Looks like a power upgrade for the house might be coming up...we have an outdated 100 amp service panel, and it looks like we'll be able to get it upgraded in the near future. (Time to replace the worn-out HVAC system with something a bit more efficient, and the power upgrade would be part of the project.) In the process, I'm hoping to add the power my shop has been lacking. (I'm currently running the whole shop on two 15 amp 110v circuits, one of which is shared with the washer and gas dryer.)

    I doubt I'll be able to swing getting all the wiring run, but I'd like to get a sufficient subpanel in the shop for current and future needs. That would include 110v and 220v circuits.

    I think ideally I'd want four 220v circuits and four 110v circuits. I figure the biggest simultaneous load I'd have in the future (after some serious tool upgrades) would be something like this:

    220v:
    Compressor 5hp 30 amps
    Dust Collector 5hp 30 amps
    Lathe 3hp 20 amps

    110v:

    Lighting 15 amps
    Bench Power 30 amps (two 15 amp circuits)

    How do I go about figuring out how big of panel to install in the garage? Is it as simple as adding up the amperage I anticipate using (with some wiggle room factored in)? Am I really looking at needing a 125 amp -- or bigger -- panel? And would this number be added to the total needed for the main house panel? In other words, say the house needs a 200 amp panel, would we now need a 325 to 400 amp panel to accommodate the subpanel in the garage?

    Thanks for any advice -
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

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  2. #2
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    vaughn, i`d suggest consulting with your `lectrition and see what he says about installing two 200 amp panels one for the house and one dedicated for the shop....most utilities don`t charge extra to hook up 400 amp service, in fact lotsa new homes are pulling 6-800 amps with all their gizmos. it`s better to know you`re covered if you find deals on tools than having to pass due to insufficient power. tod
    [SIZE="1"] associated with several importers and manufacturers.[/SIZE]

  3. #3
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    Thanks for the tip, Tod. I was wondering about that approach. Didn't know if it was possible to have two main panels.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

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  4. #4
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    Quote Originally Posted by Vaughn McMillan View Post
    I figure the biggest simultaneous load I'd have in the future (after some serious tool upgrades) would be something like this:

    220v:
    Compressor 5hp 30 amps
    Dust Collector 5hp 30 amps
    Lathe 3hp 20 amps

    110v:

    Lighting 15 amps
    Bench Power 30 amps (two 15 amp circuits)
    Vaughn,

    (I'm not an electrician, so bear that in mind, I just read these forums a lot...)

    what you are listing there are the circuit capacities. That doesn't mean that your lights are actually going to draw 15 amps (for example).

    Here, I googled up an ohm' s law calculator. According to that, if you have 4 banks of fluorescents at 70 watts a bank (two 35 watt bulbs), you are drawing 2.33 amps. So the circuit capacity may be 15, but that doesn't mean you're drawing 15.

    You need to calculate the actual normal draw of your compressor and lathe, and so on, and that will tell you what you need to know.

    The other bit of advice I'd use is the fact that I've seen many folks who seem to get along fine with a single 40 amp sub-panel in their one-person shop.

  5. #5
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    What Art said. Your load will rarely if ever be the full load rating.

    You could put a 60 amp panel in and probably never trip it. BUT, I would just put in a 100 amp sub panel in the Shop. That should give you plenty of slots for breakers and more than enough capacity. I have 100 amp panel in the lab (feed from the main upstairs) and never had a problem.

    Your electrician can give you advice too since he will be the one at your house and having to pull the wires. Thats always the hardest part. Getting wire from one place to another.

    Like Art, I am not an electrician but I learned what I know from a good one.
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  6. #6
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    I went overkill on my shop electrical and got a 200 amp box (separate service from the house) because I wanted the breaker slots, not because I needed that much power. I guess I could have gotten the big box, and put a 100 or 125 main breaker in it and would have accomplised the same thing. Jim.
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  7. #7
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    The first step in getting the shop set up when we bought our place in GA was to run electrical service from the disconnect panel on the side of the house to the shop building. I hired an electrician for this phase of the job. We decided to set a 30-position panel so I'd have plenty of space to isolate circuits. I estimate the maximum load condition to be around 60A, but if you add up the breakers I've installed the total is 330A. I have eight 220V circuits and 14 110V circuits, which fills the panel. Overkill, maybe -- but the additional cost to provide that much isolation was minimal.
    Bill Arnold
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  8. #8
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    Hi Vaughn,

    YOu are going to love all those new little electrons running around in your shop!

    When I added a sub-panel to my garage, the electrician recommended a 60 amp panel.

    I have two 220 20 amp circuits and a couple more 4-outlet 110 receptacles and added three new and NICE fluorescent lights above the major work area.

    Those 20 amp recptacles are now 30 amps. Luckily the electrician used 10 ga wire.

    What would I do differently?????

    I would have gone with a 100 amp subpanel (my 60 amp panel only has two more slots) and added 4 220 circuits and 6 more fluorescent lights.


    Joe

  9. #9
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    I've a 100 amp panel - because it was easy. The house I live in once had central electric heating. The previous owner converted to gas and just coiled up the 100a 220v line in the attic . All I did was reroute the cable back down to the main panel area (cut a lot off of course) and used it to feed the sub panel for the shop.

    The shop has 12 circuits - 4 220v, 1 15a lighting, 1 30a for the AC, and the balance in 20a.

    One thing I think I would change, I would add a second 15a for lighting or up the one to 20a. I like a lot of light and want to be able to add more fixtures without worrying about overloading. Many would advise having two lighting circuits so, should you ever pop the circuit, you will not be standing in the dark with a running tool. Seems that the chance of this happening if you have the lighting on its own circuit is pretty slim.

    Another thing to mention is that, in spite of the fact that I thought I was in overkill mode when I installed all the wiring as far as outlets go, I have found that I have needed to add 3 more duplex outlets and have need for at least two more. Outlets are like clamps - you can never have too many!

    Last item - I installed one drop from the ceiling over the workbench. I find this to be my most used outlet. I should have put another over the saw table as it often doubles as additional workspace.
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  10. #10
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    Thanks for all the suggestions, guys. Like Jim, I'm leaning toward a bigger panel just for the ability to have more isolated circuits. I've done a fair amount of 110v wiring, but I'm pretty green when it comes to 200v, so I'm not sure how many 220v circuits to plan on. I keep thinking of other tools that would likely live on 220v (like a vacuum pump), so I want to make sure I have enough capacity for them.

    Rennie, I'm thinking of having two or three power drops from the ceiling. It's either that or have power cords on the floor across the places I need to walk.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

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