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Limited power- Unisaw or no?

1K views 10 replies 6 participants last post by  bigblockyeti 
#1 · (Edited by Moderator)
Ok- current setup is 20 amp service to my small shop. I'm pushing the limits with my current equipment- only tripped it once with all the lights, older craftsman tablesaw and a shop vac.

Anywho, I started digging into my existing service. 4 10ga wires run underground.

So question: can I install a subpanel feeding off a dual pole 30 amp breaker in my main panel? It'd be limited to 30amps overall of course, but that would give me the option to get a 220v saw. Maybe a 20amp 220v circuit and a 20amp 120v circuit in the sub panel?

Thoughts? Is a 220v vintage Unisaw ok off a dual pole 20amp breaker? Or does it need a larger feed And I should forget the bigger saw and use what's working?

New shop in a year or so so I'm not going to run larger feed to this one at this point.
 
#2 ·
Well, technically what you want to do will work. But if the feed is 10-2, you won't have a neutral for the 120V circuit. I suppose you could tie the ground and neutral together together (I've seen "pros" do this). No doubt this will start a very long discussion of the "code" and what's right/wrong with your idea…..but the bottom line is you're idea will work (again, technically). If you need an approval of some sort, you may not be able to get it.
 
#4 · (Edited by Moderator)
Yes, I have 10-3 running out there.

I haven't been able to find a 30amp subpanel with a main breaker and more than three breaker lugs yet though… buying a larger 100amp subpanel is excessive, even if it's limited by the 30amp breaker in the main.

So a vintage 220v Unisaw draws less than 20a? Original motor, haven't seen a data plate yet though.
 
#6 ·
You can run a 3hp saw on 240/20A. The 100A sub may actually be cheaper then one more specific to your size needs. If it were me, I'd put in the (1) 240V and (2) 120V circuits. Put the 240 on breaker slots 1-3 and 120V on 2-4. Label your outlets so you can device your loads as evenly as possible.
 
#9 · (Edited by Moderator)
You're going to have a tough time putting a subpanel in AND running 120 AND running 240 off it.

even the 70A sub panels I've seen only have room for a single double pole breaker or 2 tandem single pole breakers.

if you want both 240 and 120 off the sub panel, you'll have to get a 70A subpanel, wire up 4 of the 1/2" breakers in it and use the "middle two" with a breaker link for your 240v circuit and each of the outer breakers will be your 120v circuits.

obviously, you'll also have to make sure that the 10/3 is coming off a 30A breaker in your panel.

at least it's my understanding that this will be what is required.
(even with the two 120v and single 240v circuits, you'll be limited to the 30A total draw)
 
#10 ·
You re going to have a tough time putting a subpanel in AND running 120 AND running 240 off it.

even the 70A sub panels I ve seen only have room for a single double pole breaker or 2 tandem single pole breakers.

if you want both 240 and 120 off the sub panel, you ll have to get a 70A subpanel, wire up 4 of the 1/2" breakers in it and use the "middle two" with a breaker link for your 240v circuit and each of the outer breakers will be your 120v circuits.

obviously, you ll also have to make sure that the 10/3 is coming off a 30A breaker in your panel.

at least it s my understanding that this will be what is required.
(even with the two 120v and single 240v circuits, you ll be limited to the 30A total draw)

-
That's my plan as of now- although I'll pick up a 100amp panel so o have more spaces.

Or maybe a load center that doesn't have a main breaker (don't need one since I will have less than 6 breakers)

Thanks all- you pointed em in the right direction
 
#11 ·
When in doubt, Unisaw! You should be fine with your setup and you'll appreciate having a Unisaw now vs. getting something smaller and then wanting to upgrade later.
 
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