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Old 07-23-2006, 08:22 AM   #1
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Help w/Welding Machine Extension Cord

I am looking to make an extension cord for my 30a 230v MIG machine and have been getting conflicting advice. It needs to be 50ft or 16m long and I hope to plug it into my dryer receptacle (230v, 30a plug, 40a breaker). I have been told by some that I need 8-3 SOW extension cord and by others that claim to have tried this say I can use 10-3 SOW. Which is correct? 8-3 SOW will run me about $17 a metre (which is very depressing) and obviously if I can get away with 10-3 I would much rather do that.

Here are the MIG machine specs straight from the manual if it helps
INPUT - Single Phase Only
Volts/Freq: 230v/60hz
Input Current: 20a - rated output
Rated Output (230v Input)
Duty Cycle: 30%
Amps: 130
Volts: 20
Output Range
Welding Current Range: Dc output 30 -175 amps
Maximum Open Circuit Voltage: 33
Recommended Input Cable & Fuse Sizes at Rated Output
Fuse Size: 40a
Input Amps: 20
Power cord: 50a, 250v three prong plug (NEMA type 6-50P)
Input Supply Conductor: (Copper, type 75*C wire in conduit) 8 AWG
Ground Wire Conductor: (Copper, type 75*C wire in conduit) 10 AWG

alos if it helps the machine came from the factory with a 12-3 8ft power cord


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Old 07-23-2006, 10:27 AM   #2
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this was taken from another forum:

Re: 10/3 extension cord for Lincoln 175 welder
Originally Posted by Weld35
wow I can't believe all the differnt oppions here. I get 8 10 12 ????????? I have 10/2 to the outlet I'm sure that will be fine with a 30 breaker. I'll run 12/3 extension cord and see what happens.

Author: MAC702 vbmenu_register("postmenu_47270", true);
WeldingWeb Foreman

"99 is correct: Lincoln's manual does indeed say to use #8. Yet, the Miller manual for the SAME CLASS machine says #14!! Now, as an experienced industrial/commercial/residential electrician I can see that Lincoln is going WAY overkill by assuming a 50A circuit at 100% duty cycle, which the NEMA 6-50 hardware is capable of. The machine itself can be powered by #14 up to 67 feet, like the Miller manual recommends. The Miller manual is using the derating factors available to welding machines. The Lincoln manual is using the maximum ampacity of the plug. They went completely different directions from "normal" 30A residential circuitry. I've always hated the lack of information provided by owners' manuals in this area, but this was especially weird.

So, in short, #14 will work up to 67 feet to meet minimum NEC Codes that apply to welding machines. #10 will meet ampacity requirements of a 100% duty cycle machine, something to which your machine could never come close. #12 is where I make a compromise as it provides more than the minimum and at GREAT cost savings over #10. The only excuse for a #8 recommendation is CYA.

Now, the wiring in the wall I would make #10, as the cost savings here are not nearly so great as they are with extension cords, and you never have to deal with the extra weight, size, and coiling resistance anyway.


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