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How many circuits and amperage needed for my attached garage workshop?

How many circuits and amperage needed for my attached garage workshop?

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  #1  
Old 08-02-11, 12:51 PM
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How many circuits and amperage needed for my attached garage workshop?

I need help figuring out what kinds of circuits to add to my garage.

I'm setting up my workshop in my attached garage. The garage is currently wired with one 15a circuit. I will have at least 5 power tools (drill press, table saw, compressor, etc.) and plan to add additional circuits. My circuit box has three open slots. I'll leave the 15a to power the lights and garage door.

Here's my question - would adding three 20a circuits be good for my setup (all tools will not be used simultaneously) OR would a sub-panel be a better choice (even though more expensive)? Also, if I stick with just adding three more circuits, does it make sense to add 30a instead of 20a?

Thanks for the advice.
 
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Old 08-02-11, 12:59 PM
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I think 20 amps is the limit on a 120 volt circuit. I would think 3 20 amp circuits would suffice but do you foresee the possibility of any 240 volt tools down the road?
 
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Old 08-02-11, 01:13 PM
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Originally Posted by kevinf. View Post
I will have at least 5 power tools (drill press, table saw, compressor, etc.)
There is a very wide range of possibilities in those tools. We need to have a better idea of the voltage and horsepower of the motors.

would adding three 20a circuits be good for my setup (all tools will not be used simultaneously) OR would a sub-panel be a better choice (even though more expensive)?
I would probably lean toward a subpanel, but depending on the sizes of your tools and your work habits even a single 20A circuit might be sufficient.

Also, if I stick with just adding three more circuits, does it make sense to add 30a instead of 20a?
General purpose circuits may be no larger than 20A. Tools that consume more power than that need to have individual circuits specifically installed for each machine.
 
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Old 08-02-11, 01:35 PM
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The tools are table saw-15a, 3/4 hp drill press, miter saw-15a, band saw-2.5a, air compressor (don't have yet), shop vac.

Also, I will use one of the circuits to power outdoor lighting...at most 2000w.
 
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Old 08-02-11, 01:37 PM
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The thought of adding a big 240 volt air compressor to my garage makes my mouth water....
 
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Old 08-02-11, 01:44 PM
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If it runs on 240 volts it isn't very big.
 
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Old 08-02-11, 01:56 PM
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Not to you but it's as big as I'm gonna get
 
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Old 08-02-11, 07:59 PM
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I would Install a 20A MWBC. The 2000W of Lights will need to be on their own 20A circut. If they are Low Voltage you will also have to account Transformer losses and Power factor.
 
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Old 08-02-11, 08:07 PM
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I agree with ibpooks. Install a small subpanel and feed it with 240 volt and 30 - 60 amps. This will give you a great deal of flexibility now and in the future for adding other circuits as needed. As a bonus you will only use two spaces in your main panel. A sub panel will only run about $40-50 plus the wire and the breaker.
 
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Old 08-03-11, 10:00 AM
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BTW, 2000W of lighting at a "shed" would be bright enough to peel paint. You can probably get by with much, much less than that.
 
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Old 08-03-11, 01:12 PM
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BTW, 2000W of lighting at a "shed" would be bright enough to peel paint. You can probably get by with much, much less than that.
He just said outdoor lighting. It might be landscaping lights, halogens, or other stuff.
 
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Old 08-03-11, 04:19 PM
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My guess is xmas lights. Think the Griswalds.
 
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Old 08-03-11, 08:56 PM
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My guess is xmas lights. Think the Griswalds.
Not even close for that. Think 400A+ Panel for that.
 
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Old 08-04-11, 11:57 AM
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The outdoor lights will mostly be for landscaping and the seasonal xmas lights.

Can anyone give me a ballpark on the going rate to have a 240w sub-panel added and line run through pipe (exterior of drywall) and across my 3 car garage ceiling? The breaker is outside, on the left side of the garage and the panel would need to be on the opposite side of garage about 30' away. I think one could just punch the new line through the back of the existing breaker and through the interior garage drywall, then routed up over and back down.
 
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Old 08-04-11, 12:24 PM
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Can anyone give me a ballpark on the going rate to have a 240w sub-panel added and line run through pipe (exterior of drywall) and across my 3 car garage ceiling? The breaker is outside, on the left side of the garage and the panel would need to be on the opposite side of garage about 30' away. I think one could just punch the new line through the back of the existing breaker and through the interior garage drywall, then routed up over and back down.
How many breaker spaces do you want? How many amps?
 
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Old 08-04-11, 12:42 PM
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Originally Posted by Justin Smith View Post
How many breaker spaces do you want? How many amps?
Based on what you said earlier: "I would Install a 20A MWBC. The 2000W of Lights will need to be on their own 20A circut. If they are Low Voltage you will also have to account Transformer losses and Power factor."

I don't think I'll need too many, maybe 4 or 5 slots of 20a each.
 
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Old 08-04-11, 01:17 PM
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ok. I'll do my best here.
The big box orange has 6 space panels for less than $20.
10AWG THHN is about 27C/ft, however you may have to buy a spool as they do not cut it at my supply house.
a 3/4'' stick of EMT is a little under $3.
My supply house carries prebent pieces for a buck or two.
Breakers cost around $5 for a single pole and $10 for a double pole.
 
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Old 08-04-11, 01:39 PM
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Thanks for the parts list and I really appreciate the all the advice from everyone.
 
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