Cable and Breaker size for Welder?

All wire and breaker specs should be in your manual, read it.

There are different ratings for cables based on whether they are in conduit, in walls, used continuously, or used for welders with limited duty cycle, or used for long distance power transmission.

You should be perfectly with with 8 gauge cable going from breaker, but breaker capacity is a different story.

The reason for the various amperage capacity ratings you see is a function of the insulaton. The higher the temperature rating, the higher the amperage capacity. Then factor in the surrounding condition: a sheathed cable will have a lower rating than one if free air. Older cable was tpically 60 C insulation, newer is 75C or 90 C. Result is that you will see ratings for #8 that range from under 40 amps to almost 60 amps.

The NEC (Section 630) allows a dedicated welder circuit to have a larger circuit breaker than normal based on the expected duty cycle of the welder. Depending on what welder you have, this may let you run wire one size smaller (ie #8 instead of #6). This is fine for an industrial setting with a master electican that takes care of a plant. I really HATE to see this in a residential setting.

Depend> I just spent 20 minutes looking on the web for information about cable

OK, I understand different temperature ratings. What would modern #8 Romex be? Does current capacity change if the Romex is in a conduit?

Richard

RoyJ wrote:

You are good to go.

Gunner

"If I'm going to reach out to the the Democrats then I need a third hand.There's no way I'm letting go of my wallet or my gun while they're around."

"Democrat. In the dictionary it's right after demobilize and right before demode` (out of fashion).

-Buddy Jordan 2001

I have a bigger (400 amp) older Miller TIG welder that is hooked up to a 40 A breaker and I can weld at about 180 A. I found that the welder drew 30A just idling and the current actually decreased when I started to weld. I think this has to do with the way the welding current is controlled in these older welders. My newer Thermal arc MIG welder will weld at 150 A without breaking a 30A breaker.

stan

Right, the 30 A is almost entirely the draw of the power factor correction caps. As the welding current increases, it becomes a smaller portion of total current, and compensates for the inductive reactance of the welder transformer. The total draw will be less at full welding current than without the capacitors.

Jon

A few extra dollars spent by the manufacturer to install a solid state relay to turn off the caps, would save the users of its equipment a bundle of money.

According to Ignoramus5429 :

That depends. Since the current is reactive current (out of phase with the voltage), it should not be charged for on a home power meter. However, I believe that some industrial ones may charge for reactive current, to encourage adjusting the power factor correctly.

Enjoy, DoN.

I agree, but some power is still being wasted, wires are being heated etc.

In my own welder, the transformer is not even energized when welding is not being done.

That is correct, some industrial users are charged basically (almost) for kVa and not power.