im wiring up the garage and want to add a circuit for my welding machine (miller thunderbolt 155dc/255 ac) which has a tag on it saying 47 amps/240 volts... heres the situation if i put on a 50amp brkr, i then have to go to #6/3 wire... i only need /2 wire as its strictly 115volt.. this is going to be inspected so i need to use the proper wire, i was wondering if backed down to a 40 amp brkr and used #8/2 if i could get away with that..ive run it on 40 amps b4 no prblm thats not the question its wether the inspector would let it go... 8/2 wire is available 6/2 can be ordered in for a premium price (more that the price of 6/3 as its rare....anyone help me with this? oh ya im approx 40ft from the service panel
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electrical question
- Thread starter RAMBIN
- Start date
Charles (in GA)
Well-known member
Are you running Romex or some sort of jacketed wire such as UF? or do you plan on using conduit?
If the max draw on the machine is 47 amps then you need a 60 amp breaker, minimum, as you do not want to exceed 80% of the breaker capacity on a regular basis (80% of 60 amps is 48 amps). I realize that you will probably never max out the welder, but you have the potential to do so, and should allow for it. You want your welder to preform properly, and if you do get a heavy job where you are drawing alot of current on a 40 amp and #8 wire you will probably have voltage drops that cause the welder to no function OK, then you will be dissatisified.
40 straight line feet from the panel? Be sure and allow for going up and over and back down if necessary. Personally, I would take #6 to a very small subpanel (4 or 6 breakers) at the welder and install a breaker in the subpanel to act as a disconnect at the welder outlet, and mount the outlet right off the subpanel. Just take #6 3 wire/w ground to it. This also gives you the potential to run other 240v or 120v outlets off the subpanel. I did this for my air compressor but I used 3/4 conduit and loose individual wires, three #6 wires and a #10 ground.
If the inspector sees the welder and what it draws, then he is going to insist on a 60 amp breaker and #6 wire.
Never heard anyone complain about overdoing wiring, but you sure will unhappy if you under do it.
Charles
If the max draw on the machine is 47 amps then you need a 60 amp breaker, minimum, as you do not want to exceed 80% of the breaker capacity on a regular basis (80% of 60 amps is 48 amps). I realize that you will probably never max out the welder, but you have the potential to do so, and should allow for it. You want your welder to preform properly, and if you do get a heavy job where you are drawing alot of current on a 40 amp and #8 wire you will probably have voltage drops that cause the welder to no function OK, then you will be dissatisified.
40 straight line feet from the panel? Be sure and allow for going up and over and back down if necessary. Personally, I would take #6 to a very small subpanel (4 or 6 breakers) at the welder and install a breaker in the subpanel to act as a disconnect at the welder outlet, and mount the outlet right off the subpanel. Just take #6 3 wire/w ground to it. This also gives you the potential to run other 240v or 120v outlets off the subpanel. I did this for my air compressor but I used 3/4 conduit and loose individual wires, three #6 wires and a #10 ground.
If the inspector sees the welder and what it draws, then he is going to insist on a 60 amp breaker and #6 wire.
Never heard anyone complain about overdoing wiring, but you sure will unhappy if you under do it.
Charles
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in the 10+ years ive had the welder ive never had to operate it wide open.. 1/8 7018 will only burn so hot....its 40 ft as the wire will bend from the brk'rs to the welding plug 50amp plug from the manufacturer..it doesnt need romex or conduit the wiring is going to be in the wall cavity its new construction..
trovato
Well-known member
When I've done wiring to install an outlet, the inspector checks the wiring and the outlet. He did not need to see what I plan on plugging into it. Who's to say you won't buy a bigger welder tomorrow? I'm not trying to tell you to do anything substandard. I would just be more concerned about what is right than what the inspector would say. This is based on New York experience, so I don't know if Canadian inspections work differently.
Also, for high amp circuits like this, I have used aluminum. It's way less expensive than copper. Everyone starts to get nervous at the mere thought, but aluminum wire is really quite safe for this sort of application. As long as you do it right and use anti-corrosion paste at the connections, there won't be any problems. That's what your service entrance probably already is. Again, this is based on New York. Check local regulations for where you live.
Also, for high amp circuits like this, I have used aluminum. It's way less expensive than copper. Everyone starts to get nervous at the mere thought, but aluminum wire is really quite safe for this sort of application. As long as you do it right and use anti-corrosion paste at the connections, there won't be any problems. That's what your service entrance probably already is. Again, this is based on New York. Check local regulations for where you live.
Junkman
Well-known member
They must do things differently in Canada, but in the US, you can't run loose wires in a wall cavity. It is either romex or in conduit. Better check with your local code authority if what you want to do is allowed.
trovato
Well-known member
I thought when he said 6/3, 8/2, etc. he was talking about cable... Gauge-slash-number of conductors.
trovato
Well-known member
Confusion here is the term "wire" vs. "cable". A single conductor vs. multiple conductors in an outer sheath.
Charles (in GA)
Well-known member
trovato said:Confusion here is the term "wire" vs. "cable". A single conductor vs. multiple conductors in an outer sheath.
Mutiple wires in a jacket = "Romex" which is actually a brand name, but is so commonly used as to become a trade name for jacketed mutiple conductor wire. That was my initial question. If 6/2 w grd is harder to get and more expensive than 6/3 w grd, then use the 6/3 w grd.
Inspector may expect the breaker, wire and receptacle to be sized the same (Ie. amp ratings) or may not care that that there is a 40 amp breaker and #8 wire feeding a 50 amp rated receptacle. Never know about inspectors. I realize wire isn't cheap, but you will never regret doing the job right, and you only do it once (hopefully)
Charles