220 VAC Advise

Big Smitty

Big Smitty

Well-Known Member
I am getting ready to have a couple of 220 VAC line run to my shop area. How many amps should I specify for each line? I want the capability to run a 2 HP grinder motor and a decent size heat treat oven. Thanks Guys!
 
OK so if I go with a 30 amp circuit it will be OK to handle a good size heat treat oven? Thanks for the information!!!!
 
If you go with a 30 amp circuit you are gonna need #10 wire not #12 . #12 is onl good for 20 amps

If you know what equipment you are gonna use already there should be an inspection plate on it that
will tell you full load amps, and max. fuse size. That should get in the ball park of what size circuits you need.
Keep in mind that you should never go over 80% of the circuit rating ,which means a 20 amp circuit is only
good for about 16 amps.
 
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Forgive me

Electrical wire sizing has a lot to do with load but also distance run. If you are adding a circuit to an attached garage with the service right there then #10 is good but if is a detached garage/shop you need to look for a wire size chart based on load/amp and distance.

An example; on the last shop I built I needed to run about 50' underground a total of 40amps thus I installed #8 and one size larger common.

On the current shop if my memory serves I am running #2 and 0 common for 100 amps. 2thumbs
 
I ran one large line (size 2, two conductor and a ground) and installed a subpanel in the shop with breakers for different circuits. The one relatively large run has minimal voltage drop for most of the loads I'm using, and the breakers in the subpanel protect the different sized wiring in the shop.
 
Use 8 in case you put in a bigger panel. I ran #8 to my 50amp panel in my outside garage. I wish now I had put in a 100amp so I could run a big compressor and weld at the same time.
 
I would defenetly put a sub-panel in your shop. At least a 50amp! I put a 100 amp in my garage. If it is a 50 then run an copper 8-3 romex or MMB basically the same thing. If it is a 100amp then run aluminum #2-3 SCR cable. Those would be the easiest and your best bet.

I just looked at my 27" even heat oven and it is a 20amp circiut. The name plate says it pulls 15amps. As for my grinder it has a 2hp 3phase motor on it with a variable speed controller. The controller converts my single phase 240v power to 3phase 240v power and it only pulls 6amps. I have it wired to a 20amp circiut. a single phase 2 horse motor I think will pull around 10 to 14 amps so a 20 amp should be good for it also. Hope this helps.
 
Hmmmm! I am not to sure about this chart http://www.powerstream.com/Wire_Size.htm ! Maybe I am not looking at it correctly but the size of wire and amps it says it can handle seem to be off to me. I have been a journeyman electrician for about 6 years now. For residental wiring this is how it works for COPPER wiring:
14 guage - 15amps
12 guage - 20amps
10 guage - 30amps
8 guage - 50amps
6 guage - 60amps

According to the National Electric Code #12 is good for 25amps so when you derate to 80% it is actually good for a full 20amps. #6 is actually good for 65amps. I would not really worry to much about the derating thing unless you are realy loading up a circuit. If I was going to put in a sub-panel with a 50 amp main breaker I would still pull a #* wire to that panel. If you realy wanted to you could pull a # 6, but then you might as well put in a 60 amp main breaker. I also wouldn't worry to much about voltage drop unless you are getting out there about 100' or more.
 
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go to you county electrical inspector and ask him. He should have all the charts and info on what size wire you should run.
 
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