Extension Cord for ARC welder

The problem is the welder plug cord isn't long enough for me to run through the tack room wall from the alley outside, to reach the 220 socket located inside the tack room. The cord is only 5 feet long and I need about 8 feet. Is it okay to put an 8 footer on it or are these things purposely kept short for power? Will this cost more than the $100 I paid for the welder (with a helmet, two chipping hammers, 3 boxes of 7011 rods, and other stuff)? I am hesitant to put longer leads on the welding lines themselves as they would have to run around the tack room door and out through the gutter to get to where I will be using the welder.

If my explanation of all this is readable enough to make sense to someone I'd appreciate your input.

John T Retired Electrical Engineer

• Hobby farm

The electrical code allows substantial derating for wire and connector ampacity for welders. Article 630 allows you to derate the nameplate primary amps by a factor that depends on the nameplate duty cycle when selecting branch circuit conductor ampacity.

A difference in length between 5 feet vs 10 feet will not have voltage drop issues.

You are better off extending the primary circuit than extending the welding leads. Welding cable is a lot more expensive than 240 VAC wiring.

One possible path is to just extend the air compressor branch circuit and add another receptacle. The problem with this is that you would then be sharing the same circuit between the air compressor and the welder. Unless you have provisions to lock out the compressor while welding, you risk overloading the branch circuit and popping the breaker, if both happen to operate at once.