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I have a an old 230 volt S.D.LEE arc welder (that I can not find any info about) printed on the front is says "PRI volts 230 max OCV 78 arc volts 25 PRI amps 65.7 SEC amps 230 temp rise 115c 60 cycles single phase model 110-085" I am not sure what that means but I think it means at the welders max setting I need 230 volts at 65.7 amps?

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I rent an old house that looks like its haunted it has an old square D panel 125 amp QO combination panel (also don't know what that means really) lots of empty slots but the combined amps not including the main shut off is 165 amps I think I need a 70 amp breaker for the welder (not sure).

Can I safely add one? If so, what conduit should I use with the 70 amp breaker to run my welder about 45 feet from the panel?

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I really don't want to burn the house down, my landlord probably wouldn't like that either.

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Since you're renting, you should have the landlord hire an Electrician. Doing electrical (or most any) work in a property you don't own, is usually frowned upon. –  Tester101 Mar 20 at 16:05
    
Your S.D.LEE welder was probably a private label built by the Century company (Century was a pioneer in infinite amp control, as the welder advertises on the face). That may help you find more information. A detail photo of the power connector(s) would help also. Electrical work will require the approval of your landlord, at the minimum. Oh, and a little google work shows: Century was purchased in 2003 by Lincoln Electric lincolnelectric.com/en-us/company/Pages/company-history.aspx –  Bryce Mar 20 at 16:08
    
the landlord says I can do whatever I want he plans to tear the house down in a few years –  chase Mar 20 at 16:23
    
what connectors would you like a photo of? –  chase Mar 20 at 16:24
    
What plug is on the end? Are there two? Is there a rating plate where the cords enter the unit? Look up the plug type at the Digital Museum of Plugs and Sockets. –  Bryce Mar 20 at 19:15

1 Answer 1

While the panel is rated 125 amp, you have a 100 amp service. You also have an electric dryer and water heater in addition to the usual lights and outlets. Adding a 66 amp load to all of this is definitely overloading the service.

If you went ahead and installed this welder, you won't burn down the house (at least not from electrical loads, from welding is another story) but you would get nuisance tripping. Every time you struck an arc, the lights would dim. The resulting voltage drop could damage electronic equipment such as computers and TVs, as well as anything else with electronics, which is virtually everything these days.

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thank you for your answer but what if I turn off the breakers for the dryer, hot water tank, and anything else I can? I am the only one living in the house I could have everything off wile welding (outside) –  chase Mar 20 at 17:53
    
A whole house surge protector can help here. And nothing says the dryer/water heater need to be on when welding. –  Bryce Mar 20 at 19:14
    
I don't see how a whole house surge protector is going to help prevent tripping the breaker if he runs the welder and the dryer at the same time. –  Johnny Mar 20 at 19:24
    
The "damage to electronics" would be from spikes, not an overcurrent trip. A 250 amp service won't change that. –  Bryce Mar 20 at 20:26
    
if all the breakers are off will I be able to run the welder or is it simply too much for this old panel? –  chase Mar 20 at 20:43

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