Setting up shopmaster 300- Wiring from panel to welder

[H2o]

Hey all, Been a while since i posted here.

So I am finally getting around to setting up my shopmaster 300. I have 240v service (actually measured it as 250v) to my garage on a 200 amp panel, residential service. This panel is dedicated to garage. Single phase.

Miller recommends a 125Amp breaker, even thought the machine is rated for 110Amp of incoming power if I remember right. It seems like the code recommends a 2 gauge copper wire or 2/0 gauge aluminum wire. But when i used a wire calculator, actually inputting the length of wire, I seems the 2 gauge aluminum wire is acceptable; I calculated a 1.955 voltage drop with 0.81% voltage drop (3% seems like the norm).

The run is approximately 25' to the panel.

Our contractor (long gone) had installed the 2 gauge aluminum wire. Looking to do things legally and if it means pulling that out I will do so.

Are there any electricians or well seasoned pros that can shed some light on this?

[Broccoli1]

Due to the duty cycle of the Shopmaster you are allowed 6g as the minimum

http://www.millerwelds.com/om/o322a_mil.pdf

[H2o]

So this chart "2-9 Electrical Service Guide" is from the panel to the plug or device?

[Broccoli1]

So this chart "2-9 Electrical Service Guide" is from the panel to the plug or device?

Both.

You need a minimum 6g wire to go from the main panel to the disconnect.
same gauge wire inside a Cord to go from the Disconnect to the machine.

Since you are using this at 240v you can use SJO cord ( J= Junior) rated for up to 300v

SO cord is rated 600v

[H2o]

One last question, I realize the manual states min gauge size, but does the building code supersede manual? Are there any electricians here that might know?

I am thinking worse case scenario, for insurance purposes if there was a problem. Some insurance companies like to deny claim, even thought fire had nothing to do with elec set up.

[H2o]

And are there any issues with using aluminum wires from panel to machine?

[WillieB]

630.31(A)(2) is a chart. Based on duty cycle of the welder, you get a multiplier you use with other articles to get conductor size. A 30% Duty cycle welder needs only .55 times the ampacity as a 100% machine. Keep in mind this only addresses the question of will it overheat? As for determining will adequate voltage be delivered? you need to calculate voltage loss. When power leaves the utility transformer some potential is lost in the form of heat. Each conductor on the way to the welder will lose voltage, each must be calculated. Most utilities deliver 240 Volts, most welders are designed for 230. They will perform acceptably at 5% under their design voltage. A 230 Volt machine works OK at 218.5. If you start with 240, you can lose 21.5 volts and be OK. Too often we hear of people calculating only the welder circuit, that power has to get to the welder circuit first.

[WillieB]

And are there any issues with using aluminum wires from panel to machine?

Aluminum is less conductive than copper, it must be larger to do the same job. A bigger concern is corrosion, more precisely, oxidation. Aluminum in contact with other metals will suffer galvanic corrosion. Terminals must be rated for aluminum, and be larger than if they are used with copper.

[Broccoli1]

Aluminum is less conductive than copper, it must be larger to do the same job. A bigger concern is corrosion, more precisely, oxidation. Aluminum in contact with other metals will suffer galvanic corrosion. Terminals must be rated for aluminum, and be larger than if they are used with copper.

If I read it correctly he had an electrician run #2 Aluminum wire for this circuit- that will be plenty for the Shopmaster.

[WillieB]

I recommend Noalox by Ideal for all aluminum terminations. It works. Get out a magnifying glass, make sure all terminals are rated AL_CU. Might have a digit between, that's temp rating. Often temp rating of terminal will limit amperage. A 90 C conductor must be limited to 75C if connected to a 75C rated terminal on either end.

[H2o]

Thanks

Thanks all for all your comments. I did put some dialectic grease on there that i had for cars. Should be same/similar stuff. I put sufficient quantity and really tightened it. Seems like the breaker connection is actually aluminum so it may be less of an issue.

[WillieB]

I believe, though I may be wrong, that Noalox has zinc, which serves as an anode to prevent oxidation in the sense galvanizing protects steel.