UPDATE - Amps through No. 6 wire

I was planning to look at welder of which I knew little except it was bigger (power-wise) than my AC-225. I did end up buying it. I was hoping to keep it in the same place and use the same plug.

That ain't going to work.

The welder is a Idealarc TIG 300/300; It is physically too big to use where my current plug is, so I will be installing a new hook-up to the back of the garage (about a 25-30 foot run).

I have some questions:

The machine tag says it draws 106 amps, and recommends a 150A breaker and No. 3 copper wire (rated for 75 degrees C). Based on NEC/NEMA charts you all linked me to last week, a 109 amp draw ought to use No. 2 wire, and if we base it on the 150 amp circuit, it ought to have 1/0 wire. Can they recommend the thinner wire based on non-continuous use, i.e., the 60% duty cycle ?

The recommended wire chart in the owners manual (see link, I hope) has a usage rate of 109 amps "With Cond." but a higer input rating of 117 amps "Without Cond." Does anyone know what the abbrieviation "Cond." stands for? "Conduit" does not make sense to me, and I don't see any reference to it in the manual.

Lastly, I plan to use a 120 amp breaker rather than the 150 recommeded (I doubt I will ever use the maximum power range on this maching which is 125 to 375 amps DC welding) Anyone see any issues with using a 120 amp breaker?

Thanks again.

Tim

• Tig 300/300 Operator Manual

Remember than in the future - this run of 3ga wire is only for a welder - you can't try to change it to a 150 amp draw for other things in a few years. :)

Welders have special instructions, and what is written in the manual should be good to go - even if it is outside what the 'regular' rules of the NEC are, you are falling into a special use situation.

--->Paul

I had a small addition put on my house a few years ago, and had the service increased to 200 amp - mainly for the jacuzzi tub and because I knew I was getting a welder sooner or latter.

The new houses they build in town are rather large and 200 amp seems to be the norm these days - no extra charge for the bigger service.

That's not what the chart does. The input amperage and the recommended breaker size goes UP in the "without cond." columns. As does the recommended wire size.

If it meant "without conduit", I would think you would not have to worry as much about heat building up, I would think all the amperages would stay the same, but you could go DOWN in wire thickness.

I think it has something to do with how the machine is put together.

Note, when I checked to make sure my link worked, I noticed that manual had been updated in 1988(same manual number as the one the former owner gave me IM-265-A), and that the input amps and recommneded wire size had been down-sized for the "With Cond." machines, which apparently means "With P.F. Capacitor" according to the updated chart. Does this sound right for being the same as "Cond."?

Note that the cover of the manual (my hard copy and the pdf file) says to use another manual for machines made before Feb 1971. My machine was apparently made in 1975. The owner gave me what appears to be the original quote he got from teh welding supplier - it was written in Dec. 1975.