Greetings,
I want to install a branch circuit in my home workshop to supply 240 VAC power to my tig welder. The circuit will be designed to provide 100 amps to the welder. I intend to use #2 or #3 stranded copper THHN conductors based on the recommendations of Miller (the welder manufacturer). The say I need a minimum of #4. The circuit will include a Square D 100 amp fused safety switch and a Hubbel receptacle configured to match the welder.
My question is…what size conduit should I use to route the conductors from the load center to the outlet? The Hubble outlet enclosure is made to accept 1-1/2″ conduit but I’m certain the size and number of conductors has a bearing on the conduit size.
If I have left out any important details or variables, just ask.
I haven’t started the work yet so I can adjust my strategy based on the info you all provide. I want to do it right but I’m not that familiar with the NEC.
Your advice, as always, is appreciated.
BillB
Replies
Around here, a typical installation like that would use #2 wires with a #6 ground in a 1 1/4" conduit.
As President, Chief Rector, Divine Ruler and Chief Secretariat of the InterGalatic Foundation for the Creative Abolition, Destruction and Demoralization of 1 1/4" conduit, I hereby request that you do not use 1 1/4" conduit. It is evil. It is also bad. Use 1 1/2" conduit instead.
~Peter
A run like this would probably be in EMT, not plastic. I take it you don't like 1 1/4" conduit?? I wouldn't either if the pull was very long.
Welders are in a category all their own, with their own code rules. When you replace the welder with a different model, the old circuit may not be enough.
At any rate, the first thing that becomes clear is that the shop will almost certainly have other electrical circuits in it - even if it's only for the lights. This means that you must now have a panel in the shop, have an outside disconnect, and a ground rod in addition to the ground wire.
You would feed the welder from this panel.
Distance, plus the fact that buried wire is considered a 'wet' location, suggest that you might very well need #1 to feed a 100 amp panel. There's really no reason not to start with a 125 amp panel, though - and larger wire.
I recently did such a run using 1-1/2" PVC. While not bad, all things considered I now wish I had run 2" PVC. The cost difference is minimal.
Again, considering the length and difficulty of the run, you might consider running even larger aluminum feeder wires to this new panel.
As I read his post, he is intending only to run wire to a receptacle for his welder, not rewire his whole garage.
The length of the run of conduit would probably determine which size he chooses.
Hello,
Bojangles is correct. My workshop is already complete and functioning. I simply intend to add a new outlet and use the conduit to protect the wiring from the outlet up into the truss space, where it will then be routed to the existing service panel.
The total run of the wire will be about 14 feet from the panel to the outlet.
I was under the impression that the size of the conduit was important due to heat build-up from the conductors. In my case, the conduit wouldn't be more than about 10 feet long.
On the topic of underground conduit, I agree that the 2 inch or larger is best. I put two runs from the house to the shop. One carries the electric and the other carries cable TV, phone and internet. Worked great except my teenage son, trying to be helpful and after all the other wires were in place pulled the cable t.v. through the conduit and neglected to pull another fish wire with along with it.
It was a good lesson in planning ahead for him.
BillB
The size of the conduit has nothing to do with heat buildup. It is assumed that it is the same for any size conduit. But rather determined the number of equivalent current carrying conductors. That won't be a factor in your case.Min conduit size is determined by the percentage of space that is filled.So it is determined by the size of the wire and the insulation type (different thicknesses for different types). And to a minor degree by the type of conduit. Different types of conduit has slightly different ID's for the same nominal size..
William the Geezer, the sequel to Billy the Kid - Shoe
You're correct; his original question was limited to simply running a circuit for his welder. Thee are two problems with that idea, though.
The first is that welding circuits go by different rules than 'ordinary' circuits. This isn't a problem if that circuit will be only for a welder - but a view of this forum will show how things change over time. Later use of the welding circuit for a different type of load can very easily lead fires and other major problems.
The second issue is that I doubt that the welder is the only thing in the garage that will need electricity. There's the rub; add anything else, or if there already is anything else, and code requires the 'complete rewire.' He's not allowed to just run another circuit out there.
If it takes a 1 1/2" go ahead and use it. That is better than a concentric washer breaking out some day. The wire goes in easier and cost is nil.