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Discussion Starter · #1 ·
I have an 80'-85' run of 8/2 wire from my panel to the garage to power my 230v welders. I'm planning to add a 230v A/C unit in the garage and want to branch off this circuit. I know the A/C unit draws 8-9 amps. My MIG only draws 20amps and the TIG draws up to 70amps max. Want to be sure if TIG welding with the A/C on that it won't be a problem.

How many amps is safe or allowed by code for this wire size and length of run?

Thanks
Craig
 

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I would say wire size is OK, but you better have a good breaker to handle that load, especially when TIG welding at the same time. Are you sure your TIG draws 70 amps that sounds like a lot. You also know branching off your main circuit may not be legal either, some States and even Counties frown on that, Don't ask me how I know,:rolleyes:
 

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Discussion Starter · #5 ·
If I'm reading the back of the TIG right it says 70amps max. at the max. output. Its only a 185amp output TIG. My MIG is 180amps output and only draws 20amps. I won't ever be running both welders so max amp draw would be 78amps at 230volts. Typically though most stuff I TIG is at 100amps output or less so it probably closer to 40amp draw maybe? Panel has 2-40amp breakers in it for this circuit.

Craig
 

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Wire is way too small. I would run 100 amps to garage with #2 copper protected by 100 A breaker in house panel. mount another breaker box in garage with separate breakers for each unit. 15 A # 14 for AC 20 A # 12 for mig 80 A #4 for tig. Here conduite is required. Rigid conduit ( buried feeder) 12+" deep. others deeper. We can use a romex type feeder but must be 4' deep and rated for direct burial. Your 8 amp AC may catch fire before blowing a 100 amp service if you were to tie them all on one. Besides your code would most likely require separate protection for each unit.
 

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Discussion Starter · #8 ·
I can't believe that it would be that far undersize atleast for just the welders. According to the links I've seen so far the 8/2 is good for 40 amps at 110volts, so it'd be good for 80amps at 208/230 volts.
I've welded alot on this circuit in the past 2 years and never popped a breaker nor has the wire even gotten warm. So it can't be all THAT far off in size.
Pulling new circuits to the garage is a MAJOR PITA at this point since the panels are in the basement on the opposite end of the house. No good chase to pull wires thru.

Craig
 

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If I'm reading the back of the TIG right it says 70amps max. at the max. output. Its only a 185amp output TIG. My MIG is 180amps output and only draws 20amps. I won't ever be running both welders so max amp draw would be 78amps at 230volts. Typically though most stuff I TIG is at 100amps output or less so it probably closer to 40amp draw maybe? Panel has 2-40amp breakers in it for this circuit.

Craig
To do this right and per code you would need at least a 100amp 240v circuit to feed the welders and use #4 wire. Even though you may never use both welders at the same time each welder is required to have at least a 125% overcurrent protection {breaker} for the largest welder would come out to be 70x125%=87.5 amps so you would use a 100amp breaker. As for the A/C ,just keep it by itself and you won't have any problems.
 

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Discussion Starter · #11 ·
Thanks Matt. So if I just pull another wire to the garage for the A/C would 10/2 work? It'd be about 60' to the panel. Then use 2-15amp breakers in the box? The A/C unit draws 8-9 amps.

Thanks for the help everyone.
Craig
 

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I have an 80'-85' run of 8/2 wire from my panel to the garage to power my 230v welders. I'm planning to add a 230v A/C unit in the garage and want to branch off this circuit. I know the A/C unit draws 8-9 amps. My MIG only draws 20amps and the TIG draws up to 70amps max. Want to be sure if TIG welding with the A/C on that it won't be a problem.

How many amps is safe or allowed by code for this wire size and length of run?

Thanks
Craig
Calculation is 2XLXKXI = wire size 2x85ftx12.9 is k factor x I is amps = 153510 is circular mills of the the wire size if you look up the circular mills in the National Electric Code book that = #8 wire. Now if you look up #8 wire in table 310-16 apacity chart #8 wire is good for 50amps. Welders need 100amp circuit.
 

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I can't believe that it would be that far undersize atleast for just the welders. According to the links I've seen so far the 8/2 is good for 40 amps at 110volts, so it'd be good for 80amps at 208/230 volts.
I've welded alot on this circuit in the past 2 years and never popped a breaker nor has the wire even gotten warm. So it can't be all THAT far off in size.
Pulling new circuits to the garage is a MAJOR PITA at this point since the panels are in the basement on the opposite end of the house. No good chase to pull wires thru.

Craig
Craig you can't add the 2 wires together for a total of 80 amps each leg is good for 50amps and they both will go to seperate bus on the panel. There are alot of variables when it comes to welding and what they draw for amperage that circuit may be ok when your at a low duty cycle or in low amperage setting on the welder but if you turn it up that wire will heat up and could possible cause a fire.What kind of electrical panel do have if its a Federal Pacific panel thats why the breaker has not tripped. There is a saying about that type of panel is You Can Weld and nothing ever trips !Even on a 20amp breaker, beware if thats what kind of panel you have.
 

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Your Tig is rated at full load amps , under normal welding conditions you are not drawing near that amperage I woul say a good guesss would be near 20-24 amp.

If you welding and the AC is on your are probably near the MAX ot the number 8 wire. Never the less it is not a safe and not within the means of what continious duty was rated for.

You should run #3 (100 amps) and feed a sub panel ( no main) feed from your home on a 100amp breaker. You dont need a "main break" breaker panel in your garage just a panel to carry the breakers for your equipment.will be less expensive
 

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As Matt said some Federal Pacifics are unsafe. Also there are some counterfeit, chinese Square D's out there which are unsafe and difficult to distinguish. I like Square D's value and buying new from a reputable source you should be OK. Also, you need a 2 pole breaker not 2 single poles allowing one to trip and the other to be live.
 

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I would suggest you use PVC rather than rigid pipe where you need bender/threaders and more expensive.

Run PVC you can buy you condilets and you can use a heatgun /propane torch to make your own bends and it is easoer and less expensive even though you have to pull a ground wire.
 

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Discussion Starter · #19 ·
Hold on.....look at this from a Precision TIG 225 (mine is only a 185 model). I must not have been reading something right on the back of my machine. This says 42amps max at rated duty cycle. So mine has got to be less than that.

 
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