Circuit breaker sizing for garage welder and compressor

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Old 04-14-08, 01:40 PM
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Circuit breaker sizing for garage welder and compressor

Hi,
I have electrical subpanel in my garage and want to install the electrical hardware/wiring for 2 tools. Need help to select correct amperage circuit breakers and wire sizes:

1st tool. Miller MIG welder; 230V 60hz single phase, Input amps at rated output=28, Max Recommended Standard Fuse Rating= 30 (supposed to choose breaker with 'time current curves comparable to a time delay fuse').

2nd tool. Ingersoll Rand air compressor; motor tag reads 230v 60hz single phase, 5 hp, Full Load Amps=22.5

Thanks in advance.
 
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Old 04-14-08, 02:45 PM
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Since you have two tools, I would run two circuits, as the welder will probably need a 50 amp breaker. What is he configuration of the plug on the welder? The compressor will be fine on a 30 amp one.
 
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Old 04-14-08, 02:52 PM
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TX for the help!

The welder plug is three prong- one circular prong and two flat prongs parallel with each other but different widths.
 
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Old 04-14-08, 03:48 PM
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Old 04-14-08, 04:12 PM
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Hello monster69SCJ,

You say you have a sub panel in your garage but it would be helpful to know what size breaker serves the garage, the wire size and distance.
 
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Old 04-14-08, 04:49 PM
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Your manual is stating the welder needs a 30 amp breaker. That means #10 wire.
 
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Old 04-15-08, 10:49 AM
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Yes, the welder plug looks like the photobucket jpg. So welder has a 3-wire cable? How to connect to subpanel since I thought 4-wire would be needed at circuit breaker (red and black wires to breaker poles, white and copper ground to bars)?


I'll check tonight for breaker size serving garage along w/ wire size and length.

Thanks very much to all of you for the help- it's really really been a big help and greatly appreciated!!
 
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Old 04-15-08, 11:52 AM
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Originally Posted by monster69SCJ View Post
Yes, the welder plug looks like the photobucket jpg. So welder has a 3-wire cable? How to connect to subpanel since I thought 4-wire would be needed at circuit breaker (red and black wires to breaker poles, white and copper ground to bars)?
Only 120/240v appliances such as dryers and stoves usually need four wires. You welder is straight 240v therefore no neutral needed.
 
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Old 04-16-08, 12:54 AM
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most resdential stick welder aka buzz box typically have 6-50R allready installed which it mean it is starght 240 volts so you only need two hot conductor and ground wire but however senice you mention your owner manual stated max 30 amp OCPD [ it can be either fuse or circuit breaker ] then you have to follow the manufacter instuction for this

you can run with 10-2w/g NM or #10 THHN/THWN [ if you run this in the conduit ] but however if you go with NM route make sure you remark the white conductor so you know it is hot conductor { use any colour marker as long it is not green}

Now next step the air compressor you should get by with 30 amp breaker but the code have specal area related to the motor you can go larger breaker only if due hard starting then you can go up much as 250% [ per nec code ] but normally 150% is plenty big for most motor useage.

22.5 X 125% = 28.125 so with 30 amp breaker you should be fine there.

and the other thing that if you are in line if sight of breaker box you are ok but if not in sight of breaker box for some reason then you must put in a disconnect switch [ unless your compressor manufacter do have sometype of disconnected switch set up allready ]

Merci,Marc
 
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