wiring a 10-2 welder into 10-3 junction box

I need to wire my welder (10-2) from a junction box that has 10-3 wire going to our hot tub.

 

Has the hot tub been taken out of service?

 

no the hot tub is still in service with a 50 amp GFI breaker.

 

There seems like a couple of things wrong with this picture,, first, you cannot share that circuit with any other devices. Second, is it a number 10 wire on this hot tub with a 50A breaker? I dont think this is an appliance that can be overbreakered in that way,,, number 6 wire I believe for the hot tub.

 

The appliance is insignificant. You can never put #10 wire on a 50 amp breaker. Code allows you to oversize your wire, but never undersize it (excepting factory installed fixture wires and such.)

That being said, step one is to replace that 10-3 with a 6-3.

Then, you'll need to run a seperate 10-2 for the welder. (I presume this is a small unit, rated at 24 Amps or less?)

 

Sure you can put a 50A on a 10, just not in this case and not most of the time. But I think it applys to 75C wire in conduit for certain machines such as welders, AC units or motors.

 

Cs, here is a dandy for you... Lincoln 255 feeder listed as, input current @max rated output 49A (230v), name plate rating is 50A and the reccomended wire is number 10 up to 100ft with a 60A breaker. Now, too light for my tastes too as they are rating for 35% duty cycle @max and 60% at 200 output. In the real world this machine draws about 30A under normal settings and came factory with an 8 cord. Just imagine cranking it up a bit on a long run, they certainly are not very voltage drop concious at best. If the input is 208 they do drop a wire size. I had never looked at the instructions until recently as we knew form experience and had them wired with 8 at about 25ft fed with a 50. We get questions in welding forum (not so much on DIY as Hobart) about sizing wire for machines. Every once in a while someone wants to put a larger machine on household service and they underwire and find that it trips on start up. They have heard you can increase breaker size if there are trips,,, but not if the machine is underwired to start with. If they underwire and just plan on keeping output current down then they need to stay with proper breaker to wire size. (this isnt for you by the way but for others dealing with motor or welders) If it is wired for full load and then IF it trips you can increase breaker size and it doesnt mean they can put a 50A machine on a circuit wired with 10 wire and 50 breaker. We could use an electrician on a couple of thse sites, especially if one has interest in welding.

 

Article 630 of the NEC covers welding equipment installations. I have not looked at it in a few years. I will look it over again,

 

If I am missing something in my understanding here I welcome the enlightenment. Usually when I think I have a grip on it I have only about half right,, yha

 

sberry, you make an interesting point regarding duty cycle and continuous load rating. I opted not to dive into that, as it tends to be a bit technical for a DIY forum. Yes, it can be done in certain circumstances. I'm personally of the belief that wire downsizing should never be done in a residentail environment. If onr dove deep enough into code, I'm sure they could find a legal exception to my blanket statement, but not one I'm personally comfortable with.

As to Lincoln's instructions, that's just a bit out in left field. As you stated, voltage drop alone is gonna come into play (normally not an issue at 100 ft. but when your overdrawing your circuit to begin with it becomes an issue.) On top of which, if that welder is seeing heavy use (fab. shop or some such) then your really giving the wiring a workout. At that point, your circuit is a glorified strip heater. I'm surprised Lincoln would give such instructions, especially when you consider the liability issues involved.

 

Cs,, yes, I agree with you about it applying to most uses of this forum. I have another feeder from a few years earlier that is half the size with a max draw of 20A that they reccomend an 8 wire on,,, go figure. I think some engineer types weere sniffin the ink when they wrote that up. Its certainly a NEMA approved piece of equipment but I dont much care for the idea of the 10 wire on my machine either. I want to feed it a healthy diet without having it in the back of my mind that I am going to be cooking some wire. About half the problems assosiated with 120 welding machines are input related, people figure that cause it has a 120v plug it can go in anywhere not realizing it is supposed to be a dedicated circuit, no cords and not a mile from the panel. I stay away from those machines and opt for 230v even in the smaller welders.