View Full Version : Welder input Amps question

WireWeld

02-07-2008, 08:56 PM

I recently got a Lincoln power mig 180c and am trying to figure out what power cable I can use for a extension cord. So, I am trying to figure out how many amps the welder draws.. I assume I need to find out the max amp draw so I can figure out what cable I can use.

According to my manual's technical specifications for the welder: for 230v input current is - 20 amps @ rated output. Does this mean 20 amp draw at the listed duty cycle rating of the welder ? That would be 130/20/30%

The welders current range is 30-180.. so when welding at 180 amp output.. it'll draw more than 20 amps ? How do I figure the max input amp draw ?

For a extension cord.. do I need to get one to handle the max amp input draw ? I am trying to figure out if I can use a 12-3 SO type of cable.. or if I'll need to go with a 10-3(about 50 cents more per foot). Also, I plan on only making this cord 25 feet long.

Thanks for any input on this :)

rickairmedic

02-07-2008, 09:27 PM

According to the lincoln site the input is 20A so a 20A circuitt should be ok personally I would go with the 10/3 SO if going 25 feet or more.

Power MIG® 180T K2472-1 208/230/1/60 130A/17V/30% 20A 30-180 Amps DC 14 x 10.15 x 18.6 66

130A/20V/30% 50-500 ipm WFS (357 x 258 x 472) (30)

Power MIG® 180C K2473-1 (1.3-12.7 m/min)

Max. OCV: 33

The 10/3 cord will carry the current better than the 12/3 one and if you ever decide to upgrade welders it will handle 30A so you wont have to make another one :D.

Rick

I replaced the crappy short input cable on a Lincoln SP-175+ with 35’ of 10-3 soow. I also replaced ground cable with a #4 and better ground clamp. May be my imagination but it seems to weld better?? Voltage drop is your enemy.

cutter

02-07-2008, 10:44 PM

Voltage drop is your enemy.

Indeed.

By all means, go with 10-3 minimum.

Wireweld, there are a couple of links in this thread from General Welding Information that you might want to file away for future reference:

Electrical Cords - types, gauges & ampacity (http://www.shopfloortalk.com/forums/showthread.php?t=5758)

Shade Tree Welder

02-07-2008, 11:33 PM

Here is a link to the owners manual.

http://content.lincolnelectric.com//pdfs/products/navigator/im/IM890.pdf

Whenever, running lines if the length is long you should go to a larger gauge wire to minimize voltage loss.

I downloaded the manual and for 240V 60Hz service they call out under input power cord. 50 Amp, 250V Three Prong Plug Nema Type 6-50P I am gonna say you need 8 AWG SO cord.

Aceman

02-08-2008, 12:38 AM

12-3 SO cord will work fine. At 25' voltage drop is NOT an issue. With a 30% duty cycle, the NEC only requires conductors capable of carrying 11 amps. The fact it has a 50 amp cordend is irrelevant.

WireWeld

02-08-2008, 02:02 AM

Thanks for the input..

I did look at those links about power cables in General welding info. And thats why I'm trying to figure out the calculations.

Did anyone notice what I am trying to understand ? The tech specs in my manual says 20 amp draw @ rated output.. and the rated output is 130amp at 30% duty cycle. The duty cycle rating is not the welders maximum welding power capability. It has a 180 amp output max rating, but at what input current draw ? Do I have the wrong theory here ? Am I missing something else ?

cutter

02-08-2008, 02:59 AM

12-3 SO cord will work fine. At 25' voltage drop is NOT an issue. With a 30% duty cycle, the NEC only requires conductors capable of carrying 11 amps. The fact it has a 50 amp cordend is irrelevant.

That may be true but it is poor economy to save a few bucks now & be limited to minimum load requirements for future use.

Thanks for the input..

I did look at those links about power cables in General welding info. And thats why I'm trying to figure out the calculations.

Did anyone notice what I am trying to understand ? The tech specs in my manual says 20 amp draw @ rated output.. and the rated output is 130amp at 30% duty cycle. The duty cycle rating is not the welders maximum welding power capability. It has a 180 amp output max rating, but at what input current draw ? Do I have the wrong theory here ? Am I missing something else ?

Wireweld, I think you are getting hung on a detail that's preventing you from seeing what you need to be thinking about.

1. While you're spending the money for a heavy duty cord, buy a heavy duty cord. You may want to plug another 25 feet or even 50 feet into it someday so don't limit it's usefulness over ten bucks. You may also wind up with a 200 - 250 class welder sooner than you think.

2. Now, look at the attachment below, from page a-2 of your manual; while it does indeed say "30 amps at rated input it also advises to use a 40 amp fuse and "Requirements for Maximum Output" - 25 amp breaker. That says to me that 25 amps is the most you can ever expect your machine to draw. Even so, I would want a cord capable of at least 25%, even 50% more than that and I would prefer to spend my money on one that will be there come what may.

What if you buy a 40 amp plasma cutter next year?

.

Shade Tree Welder

02-08-2008, 07:30 AM

Cutter you grabbed the wrong page out of the manual. You want the top half of page A-112-3 SO cord will work fine. At 25' voltage drop is NOT an issue. With a 30% duty cycle, the NEC only requires conductors capable of carrying 11 amps. The fact it has a 50 amp cordend is irrelevant.First of all rated output is at 130 amps not 180 the machines max. draw, which will be closer to 30 amps at max draw. Also going small will effect arc quality. NEC deals mainly with inductive loads (motors) and resistive loads (welders).

I downloaded the manual and for 240V 60Hz service they call out under input power cord. 50 Amp, 250V Three Prong Plug Nema Type 6-50P I am gonna say you need 8 AWG SO cord.

It has a 180 amp output max rating, but at what input current draw ? Do I have the wrong theory here ? Am I missing something else ?For general estimation

180/130 = 1.38

1.38 * 20 = 27.7 amps.

You need at least 30 amp cord or 10-3 minimum, I would go larger, it is cheap insurance. Oh wait, the manual calls for 8-3.

Nah don't listen to me or the manual, go with 12-3. :rolleyes:

Aceman

02-08-2008, 09:22 AM

First of all rated output is at 130 amps not 180 the machines max. draw, which will be closer to 30 amps at max draw. Also going small will effect arc quality. NEC deals mainly with inductive loads (motors) and resistive loads (welders).:

If smaller cord affects arc quality then by all means go larger.

For general estimation

180/130 = 1.38

1.38 * 20 = 27.7 amps.

You need at least 30 amp cord or 10-3 minimum, I would go larger, it is cheap insurance. Oh wait, the manual calls for 8-3.

Nah don't listen to me or the manual, go with 12-3. :rolleyes:

Here's the NEC answer: Looking in Lincoln's manual, input current on their chart shows 20 amps. But for the sake of Shade's argument lets say it's 27.7(28) amps. 28 amps X .55 multiplier for a 30% duty cycle=15.4 amp rated cord. 12-3 SO cord is rated at 25 amps and is more than enough.

Shade, I don't see anywhere the manual calls for 8-3 cord? It only calls for a cord capable of handling 20 amps. It says the machines power cord has a 6-50p cordend.

Now, if he's planning on buying a bigger welder or connecting a bunch of cord together than by all means buy a bigger cord. But for what he's doing right now, 12-3 is sufficient.

SlagKing

02-08-2008, 11:35 AM

Go with at least 50 feet.

Twice then what you think you need always is smart.

Tom the Seer

cutter

02-08-2008, 12:19 PM

Cutter you grabbed the wrong page out of the manual. You want the top half of page A-1First of all rated output is at 130 amps not 180 the machines max. draw, which will be closer to 30 amps at max draw. Also going small will affect arc quality. NEC deals mainly with inductive loads (motors) and resistive loads (welders).

DUH! You're right.:o

Well, the documents may be forged but the information is correct. :D

I would prefer 8-3 SO too.

Broccoli1

02-08-2008, 05:29 PM

50' 12/3 Cord and whack the ends off and replace with the 6-50 ends

Dooty cycle allows for this size- no problem

or buy for the future

http://www.brwelder.com/indextemplate.cfm?file=shop/Results.cfm

Lu47Dan

02-08-2008, 07:42 PM

With the price of copper wire head up again , I would go with the 8-3 SO cord , so when you buy your next welder (bigger :D ) your cord will be usable with it . My XMT-304 manual calls for an 8-3 conductor up to 85' total conductor length . and that is on a 230V single phase service . On 230V single phase my rated output is 225 amps . And copper wire is not going to get any cheaper anytime soon :mad: :eek: JMTC Dan

the spyder

02-09-2008, 06:32 AM

I recently got a Lincoln power mig 180c and am trying to figure out what power cable I can use for a extension cord. So, I am trying to figure out how many amps the welder draws.. I assume I need to find out the max amp draw so I can figure out what cable I can use.

According to my manual's technical specifications for the welder: for 230v input current is - 20 amps @ rated output. Does this mean 20 amp draw at the listed duty cycle rating of the welder ? That would be 130/20/30%

The welders current range is 30-180.. so when welding at 180 amp output.. it'll draw more than 20 amps ? How do I figure the max input amp draw ?

For a extension cord.. do I need to get one to handle the max amp input draw ? I am trying to figure out if I can use a 12-3 SO type of cable.. or if I'll need to go with a 10-3(about 50 cents more per foot). Also, I plan on only making this cord 25 feet long.

Thanks for any input on this :)

Where in oregon are you?

I have 30 odd feet of 12-3 and 10-3 that I would give you a good price on.

Shade Tree Welder

02-09-2008, 10:37 AM

Here's the NEC answer:

1) Looking in Lincoln's manual, input current on their chart shows 20 amps.

2) Shade, I don't see anywhere the manual calls for 8-3 cord? It only calls for a cord capable of handling 20 amps. It says the machines power cord has a 6-50p cordend.

1) The manual states the the input current is 20 amp at 130 amp output the max output is 180,

1a) Trying to factor in duty cycle is foolish. Miller and Lincoln both determine duty cycles at 40°C (104°F), you seldom have an ambient temp that high when welding. So in reality you have a much HIGHER duty cycle than is reported in the literature, do to much more effiecient cooling with actual ambient. To the degree that you can and I have often got 100% duty cycles out of my old MM 185 buy dropping the temp in the shop!

Sorry for confusing the text book answer with real world experience.

2) Wrong! See attached file. It clearly calls for a 50 amp power cord.

50' 12/3 Cord and whack the ends off and replace with the 6-50 ends.Ed, not a good idea.

Aceman

02-09-2008, 12:46 PM

1) The manual states the the input current is 20 amp at 130 amp output the max output is 180,

1a) Trying to factor in duty cycle is foolish.

That's your opinion. Using your previous calculations of 28 amps 12-3 SO could be used up to an 80% duty cycle.

2)It clearly calls for a 50 amp power cord.

No, it doesn't. It says the power cord has a 50 amp, 250v cordend on it(6-50p). Look at the 140 models chart below. It lists the recommended cord conductor size in a different box(extension cord). Besides, why would they recommend a 50 amp cord fused at only 40 amps?

FYI, 8-3 SO cord is only rated 40 amps. So I guess he should buy some 6-3 cord(rated 55 amps), you know, just in case he might try and run his welder at a 100% duty cycle like you do.

Use caution when using this and other calculators for house wiring, some don't go by the NEC code for house wiring.

Using the calculator http://www.csgnetwork.com/voltagedropcalc.html

10 ga cord.

30 feet long. because 25 feet is always short.

27.7 amps.

It comes up with a 2 volt voltage drop.

===

This is rough math that's close enough for the question.

===

Using ohms law calculator. http://www.angelfire.com/pa/baconbacon/page2.html

230 volts ÷ 27.7 amps = 8.303 ohms. Resistance load of the welder.

2. volts ÷ 27.7 amps = .0722 ohms. Resistance of cord.

Adding the resistance of the cord to the res. of the welder = 8.375 ohms.

230v ÷ 8.375 ohms = 27.462 amps.

27.7 amps - 27.452 amps = .248 amps.

180 amps ÷ 27.7 amps = a ratio of 6.498

.248 amps x 6.498 = 1.6 amps. output loss.

===========

Bottom line is.

Using a 10ga, 30 ft cord.

Will reduce the input current by 0.248 amps.

Assuming 180 amp peak output current. would be reduced to 178.4 amps.

I would go with the 10/3 for an extension cord in your case.

If it was house wiring I would go by the NEC book, but NOT under rate the wire as stated in the NEC book under WELDERS.

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