I agree with 3 hp being the 17 or 18A,,, but the unit in question was 13A,,, That is Ingersolls version of 3 hp,,, ha

 

I really think he needs to have a licensed electrician wire his circuits.

 

Hey mike, I'm not disagreeing with you for any reason other than the only authority's calculations that are gospel in doing any electrical projects should be the NEC. I would have to say that if following code requirements has made his garage project too complicated then I too think he should hire a licensed electrician as these are the rules that should be followed and have been made only for the sake of safety. Hopefully he will keep going with his project, I agree.

 

ATTN:bob-63-292:
Wiring for new tools is cool. I have been using a Lincoln 225 stick welder in my backyard for quick repairs, but when I need to crank it up to settings above 100-120 amps (welding heat/power) settings, the 30 amp 220v clothes dryer circuit that I plug my welder into can't handle the load, If the repair job that requires higher settings on the welder can't be moved, I have to pull the kitchen range out and plug my welder into the 50 amp receptacle . It is not fun to pull your stove out, finish the job, and then re-install your stove. Wire the welder outlet for 50 amps. Wire the compressor outlet for the "motor-start"amperage and make sure that the compressor motor has its own over current protection to protect itself while it is running. You will need to get an "electrical work permit" from your local city hall to add the new electrical circuits. The permit is cheap, and while you are applying for it, the inspector may be available to answer all of your questions concerning wire sizes, voltage, circuit breakers, etc. (Unless he/she is out of the office inspecting work done by other permit holders - they have to work too!) Electricity is around us everyday and most of us aren't familiar with how it is routed(by wire) and how much is used (watts,amps) and how to plan future use. A wonderful book has been available, It is titled:Wiring Simplified. The book is published by:
Park Publishing, Inc.
511 Wisconsin Drive
New Richmond, Wisconsin 54017
The wiring book will answer many questions any amateur electrician may have, and will help a person to plan their own electrical work.and remind the amateur that his/her work must be inspected&approved before it is put into operation. By the way, "Wiring Simplified" is available in most hardware stores or building supply outlets. If you cannot find a copy anywhere handy, go to a bookstore and the ISBN number is as follows:ISBN 0-9603294-8-x Good luck with your wiring!
I'm in the process of building a workshop that will prevent plugging my welder into the kitchen range outlet!

 

Doesn't this apply if only one motor is on the circuit? If more that one is on the the same dedicated branch, then it is sized by using 175% of the largest motor times 60% of the remaining motors fla. What I'm trying to say is. If there is a chance that you will use a large floor mounted grinder, or any other motor on the same branch, then you will be back to square one. Which means new breakers and wire. Just a thought.

Clay

 

Clay, you are probably more up on multiple motors than I am as its been a while since I have read much of the section on motors and it usually gives me a headache anyway. I think (just a thought) that most of that relates to refrig and ventalation equipment or similar applications with multiple motors on the same process although I spose it could also deal with seperate appliances on the same circuit. It would almost certainly fall under the "industrial with proffesional supervision" type thing. Most guys here should certainly have one appliance to a 230V circuit in most cases and lots of times on other forums we tend to recomend matching the wire size to breaker rules just so some unsuspecting type doesnt come along after the fact and assume cause it has a 50A breaker that its a continious 50 a circuit. The thing that often comes to mind is a welder circuit being used as a kiln circuit when propeerty changes owners. Just imagine someone coming along and saying ah-ha, a 50A circuit and not knowing it is on 10 wire, socking that kiln on it for 8 hrs and going off to bed.,,, just some babbling on my behalf, worth looking up though.

 

You also need to remember that the AMP rating is for "Two Legs of the Circuit 240Volts plus ground" So you rating will divided by two not one. So you only need a Two Pole 30 and number 8 wire size.

I use my fluke 336 to check FLA and in rush at start-up to be sure the motors are working right.

 

The max you can load a breaker by NEC (national electeical code) article 210 is 80% for lights, appliances ect. A welder if portable can have a breaker overcurrant rated at 200% of welder rated amperage,the conductors to the welder at 50% minimum of rated amps. This is for portable welders only and operated as a nonautomatic welder, article 630-31 (A) sub (1). I'm a licensed aircraft mechanic and a I.B.E.W. electrician. Carl.....................o&o>..................... .............................

 

you really need a 50 Amp breaker to run the welder and the compressor