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General input wire advice

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  • General input wire advice

    I have a shed about 150 feet from a utility pole. The pole has a breaker panel servicing the house. I want to buy a Miller stick welder for use in the shed with a max DC weld of about 200 amps (for rare instances, mostly though I'd be at 150-180 amp settings).

    A few general questions to get me in the ballpark before I start talking to electrical contractors and shopping for wire, breakers, panels, etc.

    First, what size wire does it sound like I'd need for the 150 foot run from the pole to the shed ? I would not be running anything else in the shop other than a few 100 watt bulbs while welding (mostly ranch stuff- tractor mods, etc.) and think the duty cycle would be fairly normal or low.

    Second, what kind of buriable electrical conduit should I be looking for for the run to carry the wire ? What's it called and is there a specific number correlating to the wire size you're running through it ?

    And finally, would there simply be a subpanel and single additional breaker at the utility pole, and then another subpanel with additional breaker at the shop ?

    Is there any website that gives tables of wire gauge, amperage and distance ?

    Thanks for any general information on this kind of setup.


  • #2

    I am just finishing up that sort of things. I ran 4-0 aluminum from the meter to the breaker box. I need 200 amps to run my TIG unit. Plus I have serveral other things in the shop, but few would ever be running at the same time as anything else.

    My cabling route is sort the following, in the shop, from the breaker boxes, (I have two for control over each machine or services, in short lots of breakers) it exit the building goes into 3 inch PVC conduit that is buried 24 inches or more under my drive way, I also pulled a phone line and Cat 5 wire and wish I had taken some RG 59 or Rg 6 for TV service also.

    Then the conduit emerges across the driveway, goes up along the side of the house. The 4-0 wire goes across the side of the building just below the siding, with metal cable clamps and concrete screws hoding it up. Then it enters the house next to the houses breaker box. That is where I am hooked up.

    Digging the trench wasn't that hard, I couldn't get a trencher in there which out digging a couple of pits and then it wasn't that far by using a oick axe, shovels, wrecking bars and post hole diggers.

    Hope this helps. Amy questions just ask.



    • #3
      Originally posted by bcarwell View Post
      A few general questions to get me in the ballpark before I start talking to electrical contractors and shopping for wire, breakers, panels, etc.
      You probably should go ahead and contact a licensed electrician in your area. He/She will be aware of the code requirements for your area. Most follow the NEC, but local jurisdictions can, and do, vary in some specific requirements. You might also stop by your local Home Depot, Lowes, or other home improvement center and browse the book/magazine racks I've seen in every one I've ever been in. You should find some publications that will be very helpful.

      The wire gage needed is a function of the length and total amperage it will need to carry, and whether or not it's buried in conduit or suspended in free air. You need to get a handle on the maximum amperage the service will be called on to provide and the total path length of the cable run.

      I believe most codes allow direct burial of Service Entrance (SE) or, in some cases, Underground Feeder (UF) rated cable without requiring that it be contained in conduit. If you use buried conduit, and I recommend that you do, the grey PVC conduit is probably your best bet. Minimum size of the conduit will be determined by the total number of wires and the size of those wires and depth of burial will be specified by local codes based on the frost depth.

      The number, positioning, and content of required panels would be best addressed by someone intimately familiar with your local codes.

      Of course, all bets are off if you plan to do the installation yourself without interference ... er, uh, ... benefit of local Code Enforcement Officers. If so, however, should it come to the attention of those official (some might say officious) watchdogs, be prepared to either tear it all out or pay a much inflated price for a permit and prevail on a licensed electrician to sign off on the work.

      That said, I recently enlarged my workshop and upgraded the electrical service from a 60 amp branch drop from the main residence service entrance panel to a 100 amp service entrance at the shop fed from the utility transformer. The run was about 200 feet in buried PVC conduit (2", if I remember correctly) and I used 2ga copper for the hots and 4ga for the neutral - since the majority of the use is 240v, codes allowed a smaller neutral wire. I think a smaller wire may have met code, but I opted to go larger just in case I eventually needed more than 100 amp on the service.

      In my particular case, since codes required a single point cutoff for all service from the transformer, the feed from the transformer went to a cutoff panel beside the transformer and the 200amp house service and the 100amp workshop service branched separately from there.

      I repeat, get the advice of a local, licensed electrician if you feel the least bit of uncertainty about the requirements for the installation.


      • #4
        Here's your wirre size calculator...

        Here is a link to an on-line wire size calculator. Hope this helps.

        BTW: I helped a buddy in Oregon run power to his garage. He pulled a permit and we did the work. My electrical license is in Texas not Oregon. All the work was done to code and looked great. When the inspector came out he nitpicked it to death. We fixed what he didn't like and called for another inspection (only the first is included in the permit fee). He found four or five new things he didn't like. To make a long story a little shorter, my buddy had to hire an electrician to sign off on the work he and I had done before the inspector would pass it. $150 to sign our permit without ever touching a single wire!!! Then it passed with flying colors.

        Bottom line: Be prepared to hire an electrician if you need a permit.


        • #5
          [QUOTE=triggerman;5042]Here is a link to an on-line wire size calculator. Hope this helps.

          Thanks for the heads-up.
          BTW, I did not see the link to the wire calculator you referenced above. Maybe it was my browser....



          • #6
            get yourself an Ugly's electrical reference book. its packed full of info. will tell you max recommended amps for wire in ground and free air, how many wires you can fit in different size conduit. i used it when i did the wireing for my garage.


            • #7

              Her is the link:


              Give it a try.


              • #8
                My math and rules of thumb still hold true for my place. 4/0 worked just right for me.

                Many thanks for the calculator,



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