View Full Version : newbie: will 12-3 wire handle 220v 30amp circuit?


t100
05-07-2010, 04:16 PM
need to wire my portable tig welder. it's a Miller Maxtar 150STH with Auto-Line. the machine can be hooked up to either 110v or 220, single phase, it will automatically sets up itself accordingly.

it comes with a 6ft 110v plug, and I have a 20amp 110v extension cord already. now, I need to rig up a 220v extension cord. I have 50 ft of good American made construction grade 12-2 wire(2 wires plus ground, total of 3 wires), will it handle 30amp?

nate379
05-07-2010, 04:21 PM
110v/220v are you in Europe? I'm just asking because here in the US it's 120v and 240v.

12 AWG would be ok for it on a welder, but I'd go with 10AWG for a cord that long.

Todd.Brock
05-07-2010, 04:27 PM
The ground is assumed when you are referring to romex. 12/3 has 3 conductors and a ground. 12/2 has 2 conductors and a ground. It is my understanding that 12 ga wire is only good up to 20 amps. Its not for making an extension cord, although I have seen it done countless times. For an extension cord, I would use 10 ga. SOOW which is neoprene (I think) exterior, stranded, insulated and resistant to oil,water, abrasion, etc. You can get it at lowes. Feel free to chime in if Im wrong!

t100
05-07-2010, 05:04 PM
label on the wire says good for 15amp 110v. does it make it 30amp when increase the voltage?

I have total of 50 feet wire, but only need 25ft to make an extension.

sberry
05-07-2010, 05:20 PM
For the welding machine the 12 is fine, not for general use circuits. That machine will only pull 20 on 240 wide open and is duty cycle rated. I believe it comes with a 14 cord so the supply wire you are using is a size bigger which is great.

nehog
05-07-2010, 08:17 PM
label on the wire says good for 15amp 110v.

Something is wrong there... Aside from the 110 volt issue (the US is 120/240), if it is a 12 AWG copper cable, the 15 amp spec is wrong.


does it make it 30amp when increase the voltage?


No! Amps are amps, voltage is voltage. neither is related WRT wire size. Drawing 50 amps through the wire at 10 volts will generate as much heat as drawing 50 amps at 1000 volts...



I have total of 50 feet wire, but only need 25ft to make an extension.

If true 12 AWG wire, you should be OK, but what does the specification plate
on the welder say is the current required at 240 volts?

t100
05-07-2010, 09:32 PM
Something is wrong there... Aside from the 110 volt issue (the US is 120/240), if it is a 12 AWG copper cable, the 15 amp spec is wrong.

http://i638.photobucket.com/albums/uu105/nwstindy/CIMG0057.jpg

No! Amps are amps, voltage is voltage. neither is related WRT wire size. Drawing 50 amps through the wire at 10 volts will generate as much heat as drawing 50 amps at 1000 volts...

I thought that was the idea of hi-voltage power transmission, same amperage by using higher voltage to utilize smaller transmission line wire diameter.


If true 12 AWG wire, you should be OK, but what does the specification plate
on the welder say is the current required at 240 volts?

I pulled the ol' operator's manual. it says for 12ga. wire extension, maximum length is 91ft.

trythis
05-08-2010, 07:46 AM
Does that 91 feet include the 12 gauge wire in the wall? If you have a 100 foot 12 GA run to the outlet from the breaker, you would need to run a different 10GA wire circuit to a 20 amp receptacle, then you could use your extension cord.

Professur
05-08-2010, 08:05 AM
The 15A on that package is referring to the end connectors. They're rated at 15A. The wire would go to 20A, with better connectors. They build extension cords like that to reduce voltage drop over the length of the wire.

bradleys
05-08-2010, 11:02 AM
I thought that was the idea of hi-voltage power transmission, same amperage by using higher voltage to utilize smaller transmission line wire diameter.


High voltage transmission is used to increase the "power". Multiply amps times volts, and you get watts, which is the measure of power. The amperage capacity of a wire is related to its resistance and the amount of heat you're willing to accept from the wire. The amperage is relatively fixed for a given wire size and metal and insulation. Increasing the voltage gives you more power. There's also "voltage drop" which is related to amperage, and is more important with lower voltages.

Google for "ohms law pie chart". You'll find a variety of graphical quick references which explain the relationships between ohms, amps, volts, and watts.

TheGrooveking
05-08-2010, 11:20 AM
Guys a few things need to be cleared up here, first off NOT all 12 ga wire can handle 20 amps! One of the things that allows for instance THHN 12 ga. wire to carry 20 amps is the temperature rating of the insulation, so don't automatically associate 12 ga with 20 amp capacity.

Secondly, the length of the conductor matters, a 100' extension cord of 12 ga is not what you want for even 20 amps, if you search around you'll find amp ratings/ wire gauge / distant charts that will show you what you need.

As to the electrical service you provide a welder or any other electrical item the key to doing it correctly is basing the equipment full capacity need as your 80% of the electrical feed. So if your welder requires 30 amps, then you'll want to put it on a 40 amp circuit. I know many will argue that you won't be running the welder at full output, but if you need it, you need it.

TheGrooveking

nate379
05-08-2010, 01:00 PM
I have never heard of doing that for a welder. Usually you run a 30 or 50 amp circuit depending on how big the welder is. For a 50 amp run, 10 gauge is ok per NEC as well.

t100
05-08-2010, 01:49 PM
sorry for the confusion, I was hoping to pull a quick answer, being too lazy to hit the books.

30 or 50amp circuit will not work on this suitcase welder. it's small, size of couple lunch boxes. it's designed to be mobile, not for production. the argon bottle I bought for it is only 2 feet tall. you can lift the welder with your pinky.

http://www.millerwelds.com/resources/articles/GTAW-TIG-Welding-Larsen-motorsports/

for home, the extension cord will be pigtailed directly to the breaker. for track side, will be plugged into a 3k generator.

I was taught always use bigger wire, smaller breaker. I need a 20amp breaker, at least use the wire can handle 30amp. that's why I'm asking.

I have this 100' of 12ga cord, 50' will be used to make a 110v extension. if I can get away with using the left over to make a 25' extension cord for 220v, why not. it'd be better if I buy 25' of 10-2 wire but it more heavy and another $50.

still seems 12ga is border line workable.

I'm kinda hesitate to cut this $100 extension cord.

nate379
05-08-2010, 02:18 PM
Why would a 30 or 50 amp circuit not work if the welder only pulls 20 amps? :headscrat

Don't know who taught you the bigger wire thing but they must have had money to burn for no good reason.

Generally 20 amp circuit is 12 gauge, 30 amp is 10 gauge, though for a welder you can go smaller per NEC because it's not a constant load. Outlet gets marked welder use only. When I wire a 50 amp outlet I just run 6 guage though, just in case I want to plug in an RV, hot tub, oven, dryer,etc, etc to it.

Also are you in Europe or Asia? You keep saying 110v/220v and that is confusing everyone in here. In the United States it's 120v/240v.

sberry
05-08-2010, 02:32 PM
Going to higher V, 240 improves performance of the wire in a sense, one needs to remember this type of machine is duty cycle rated, it doesn't run at 20A draw continuous, overloading this wire, the 12 is not an issue with this machine no matter how big the breaker is. Only reason to have a 30 is nuisance trips that might come from a 20. At extreme distance a larger wire would be more helpful as would running it on 240 vs 120, but,,, most of this is moot with this particular unit, the operator would never be able to notice the difference with 10 vs 12. As to the electrical service you provide a welder or any other electrical item the key to doing it correctly is basing the equipment full capacity need as your 80% of the electrical feed. So if your welder requires 30 amps, then you'll want to put it on a 40 amp circuit. I know many will argue that you won't be running the welder at full output, but if you need it, you need it.
Actually the wire could be undersized with a welder.

sberry
05-08-2010, 02:34 PM
Not that anyone thinks this is a great idea but some installations may be legal for a welder with number 12 wire and a 50A breaker.

t100
05-08-2010, 05:19 PM
Why would a 30 or 50 amp circuit not work if the welder only pulls 20 amps? :headscrat

Don't know who taught you the bigger wire thing but they must have had money to burn for no good reason.

Generally 20 amp circuit is 12 gauge, 30 amp is 10 gauge, though for a welder you can go smaller per NEC because it's not a constant load. Outlet gets marked welder use only. When I wire a 50 amp outlet I just run 6 guage though, just in case I want to plug in an RV, hot tub, oven, dryer,etc, etc to it.

Also are you in Europe or Asia? You keep saying 110v/220v and that is confusing everyone in here. In the United States it's 120v/240v.

I'm in Indy, label on the welder says 115v/230v. I think everybody gets what I'm talking about 110/220v.

20amp breaker is all I need. this is a portable welder not production. I want to have to use the 12ga as long as it's safe. I need to fit everything in the suitcase box.

mrb
05-08-2010, 05:34 PM
ive got some L6-20 twistlocks (these are the 20 amp 240v 3 pole version for this application) if you need...............

sberry
05-09-2010, 09:42 AM
20amp breaker is all I need. this is a portable welder not production. I want to have to use the 12ga as long as it's safe. I need to fit everything in the suitcase box. Yes, it is safe. I got mine tucked in a grab bag too. There is a cord there but I guess its not in the pic. I ran mine on 240 in the shop to test when I got it but since have never used it, always on 120, thats where its convenience shines. 1/8 6011 and 3/32 7018.

yotarover
06-17-2010, 12:30 AM
well in that case what size drop cord should i run for my HH140
my building where i'll do most of the welding is ( 63 1/2 ') from the nearest 120v outlet .

the box in the house is old school shotgun shell type fuses with 4 screw in 30amp's

my house was built in 1965 will the wiring hold up to welding?