No announcement yet.

wire sizing

  • Filter
  • Time
  • Show
Clear All
new posts

  • wire sizing

    I have a shed that I want to run some power into. I will be using a 225 Lincoln arc welder, a few lights and an automatic door opener. Obviously there will be a couple of recepticles, no more than 6 or 8 probably. Its for personal and not commercial use.

    Will a 100 amp box be enough and what size wire should I use to get there? it will be coming off a 200 amp service about 80 to 100 feet away and run through conduit underground. I don't want to undersize the conduit when I bury it nor do i want to waste the money on oversized fittings and wire.
    Work hard, Play hard, Sleep easy.

  • #2
    plumber, 100 amps is plenty for a 50 amp welder. #2 gauge wire in a 1.5'' conduit will work fine. i suggest that with that open ditch , run an extra couple of conduits. low voltage security, telephone, and cable can go in 1. maybe a set of switch legs for a 3 way lighting circut in another. don't forget that new water and gas line too. maybe an air line too.


    hope you don't blow a fuse when you read the flat rate thread
    phoebe it is


    • #3
      What is the rated volts ,amps, and/or watts for your welder?
      If it is 50 AMPS then you'll need more than 100 amps, depending on how many tools will be used at same time.

      #2 AWG is rated at 115-130 for 167-194 degrees Fahrenheit.
      Run a 8 AWG ground with a ground rod for the sheds panel.

      If you are also going to put in an electric heater you may want to use a 125 amp panel instead just in case you use a few tools at the same time. It sounds crazy but I'd do it that way in my future shop
      I would then have two 20 amp breakers for the 4-5 outlets and the remaining outlets and the garage door opener on the other.

      Depending on the needs of your arc welder it should have a dedicated circuit.

      One 15 amp circuit for the lights. Some people will just tie the lights in with their outlets. I don't think there is a code issue doing this but if you trip a breaker when you're working at night.......

      Hope this helps
      "Diplomacy is saying nice dodging until you can find a rock." Will Rogers
      "If a Monkey can do your job, are you in the right profession?


      • #4
        If you have accses to an electrical code book Article 310.60 shows the wire insulation type and the rated amperage and certain temperatures.

        some basics.....
        #14 awg 15 amp breaker for lights
        #12 " " 20 amp breaker for outlets and garage door opener
        #10 " " 30 amp breaker.... used for clothes dryer
        #8 " " 50 amp breaker... used for stove

        I'd have my outlets GFCI protected and rather than get a GFCI breaker 2 GFCI outets will do fine. With the line side from one powering your garage door.
        "Diplomacy is saying nice dodging until you can find a rock." Will Rogers
        "If a Monkey can do your job, are you in the right profession?


        • #5
          I ran 4 gauge wire from my main 200 panel to my garage 100 amp panel. Run is right at 100 ft. I put in several breakers 20 amp for tools, a couple 15s for lighting. And run several outlets for my welder, Exhaust blower and DC system, all 220v My welder is a Lincoln AC/DC 225 and I have not had a single electrical problem in the 14 years since I built the garage.
          info for all: --- "I like long walks, especially when they are taken by people who annoy me."


          • #6
            Most stick welders require a 50 amp circuit. With some lights on too, your current draw will probably be around 50 amps. 100 amps is more than plenty for that garage, however I wouldn't go less. You can get away with 3 AWG copper or 2 AWG aluminum for 100 amp service. Aluminum is as good as copper when it comes to feeders and is much easier on the wallet.

            Personally I wouldn't install the wire in conduit unless you live in a region that has a lot of rocks in the soil, you are burying below a concrete or gravel driveway, or you have alot of burrowing type animals such as gophers, woodchucks, etc. Underground conduit retains water and if you don't use the proper wire it will eventually lead to failure because the water will break down the insulation. So either use URD which is a direct burial wire or use conduit and a wire that has a W rating such as THW/THWN or RHW. Also when using a complete conduit system you should consider using expansion fittings on the vertical risers. I would use 2" conduit because there isn't much price difference between the 1-1/2 and 2 and when pulling wire in distances the extra room makes it much easier.

            You need to run 4 wires from you house panel to your new garage panel. Two hot legs, one neutral, one ground. This is a bonding issue in which the code calls out that any remote breaker panels must have an equipment ground bar and you cannot bond the breaker enclosure to the neutral bar with the green screw/copper strap provided by the manufacturer. The neutral/ground bond must occur only at the first disconnect which would be your house panel or possibly a disconnect between the meter and the house panel. Grounding/bonding is an extremely complex and sensitive issue to which most electricans don't have a full understanding of the issue. I won't claim either to completely understanding it, but the 4-wire feeder is a must. For 100 amp service a 6 AWG wire is sufficient and can be bare or insulated.

            Polar sparky made a good suggestion, I would not use the GFI circuit breakers, they are overpriced for this application. Just use a couple of receptacles. I never use to believe in running the garage door opener on a GFI protected circuit. But I now include the door opener receptacle on the GFI circuit because the it can "sometimes prevent" damage to the electronics of the opener in the instance of a small voltage surge.

            IMO, I would definately throw in a couple of 1" - 1-1/4" conduits for future needs. One conduit for low voltage and one for line voltage stuff. Conduit is cheap and you will appreciate the few extra bucks you spent later if you decide to add.

            Wow, that was a little long. But hopefully you have a better understanding with everyones suggestions.
            Last edited by sparkynames; 01-29-2006, 05:53 PM.


            • #7

              Have you considered asking the power company to run seperate dedicated line to the shed? Dont know about your area but here in Alabama they ran a dedicated line and seperate account to my barn. Of course, I pay more since I dont benefit from the tiered structure they have for charging for it.

              I did not require a second transformer or additional poles.

              It is impossible to make anything foolproof because fools are so ingenious.


              • #8
                Thanks for the replies everyone. After doing a little additional research and since there have been new and unexpected demands on my free and spare time it looks like I will have to buck up and hire a good electrical contractor to do this for me. Since I am spending the money for these guys now anyway I will be upgrading a lot in my home and other shop as well.

                Rest assured it will not be a flat rate outfit..
                Work hard, Play hard, Sleep easy.