Breaker Size?

[kneedeep]

I have a Miller Thunderbolt AC/DC machine in a shed that has been wired with a 100 amp sub-panel. The feed from the main is about 160' to the Equipment shed with 2/0 Aluminum wire with a ground rod. Most of my welding is repair and medium size fabrication.
My question is, what size breaker would the welder require to operate?

TIA

 

[John Fitzgerald]

Probably a 50 amp two pole breaker would be fine. Three wire #6 copper plus ground to the 50 amp outlet.

 

[gary49]

Receptacle that fits the plug on welders is generally 50 amps. Breaker should be 50 amps. Only 3 prongs on the plug, so 3 conductors, 2 rated at 50 amps, the 3rd conductor is the ground, could be as small as 10 gauge copper for that one. Least expensive cable to use would be #6 aluminum service entrance cable.

 

[John Fitzgerald]

Some locales specify four wires for all 240V circuits. I agree not needed for a welder.

 

[grsthegreat]

there will be a name plate on the welder. my thunderbolt lists 50 amps. dont need a neutral on welder. only 2 hots and aground

 

[medic0648]

Depending on how far from the panel, the duty cycle for the welder, and if you plan on upgrading to a welder with a higher duty cycle here are a couple charts to help. Below 100 amps use the 1st column and multiply using the derating factor for the duty cycle. Or don't de-rate and you are good for 50 amps non continuous use.

 

[Fallon]

Depending on how far from the panel, the duty cycle for the welder, and if you plan on upgrading to a welder with a higher duty cycle here are a couple charts to help. Below 100 amps use the 1st column and multiply using the derating factor for the duty cycle. Or don't de-rate and you are good for 50 amps non continuous use.View attachment 527482View attachment 527483

 

[dragoneggs]

Some locales specify four wires for all 240V circuits. I agree not needed for a welder.

Yes, I understand 4 wire is code in WA state.

 

[Eric102]

Yes, I understand 4 wire is code in WA state.

I wonder if that's a recent change? When I built my house in 2000 the electrician put in a 50 amp 3 wire in the garage for my welder.

 

[buickanddeere]

Personally I avoid derating. I just stick with the standard NEMA guidelines. Wire Current Ampacities NEC Table 310-16 A bit more expensive for the extra copper, but no chance for confusion or problems down the road. I do tend towards overkill though. Makes upgrading easier.

I also go with NEMA L14-50 plugs. 50@ of 120v or 240v power. You need an extra wire for it, but you gain flexibility. Most generators in the 50@ range will use this plug so it makes it easy to go mobile if needed. It also becomes easier to make a sucide cable & back feed your house if needed as well. Although if you couldn't figure out from the cable name, that's not always the smartest move.

How pray tell so you obtain a ground , neutral and two live lines from a three prong plug and receptacle ? Anyone advocating the use of a double male suicide cord and without a fail safe transfer switch. Their opinions should be ignored .