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  • New sub panel

    I need to run electric to a new out building and i just wanted to check my thinking.

    I will putting a few lights, 1or2 20amp circuit outlets, and a 30 amp 220v for an air compressor.

    I plan on running 2-2-2-4 al service wire to a panel with a main breaker (used for the disconnect) the out building is about 150' from the service panel I am pulling from. it is a 200amp service just serving a garage, lights and water heater for a 1/2 bath and an oil furnce.

    Question is with that distance is it still ok to put a 100amp breaker or should I go smaller?

    Do i need a ground rod since i am running one from the main panel?

    Is this overkill for all that we need?


    thanks

  • #2
    Re: New sub panel

    If you are running underground you will need to use conduit and use the proper wire like THHN. You must upsize the wire because of the run. 150feet is quite a ways and it also depends on your load. Thing is, your load may be small now but later you may increase it so I would plan for that. Therefore the wire size may vary depending on the load calculation. Once you have the wire to the out building panel which will require 2 hots, a nuetral and a bond wire (4 wires) you will treat the sub panel like a sub panel by seperating the nuetrals from the bonds in the panel and sinking 2 ground rods at the out building. The code has changed on this from the past. it used to be you could run 3 wires. 2 hots and a nuetral treat the sub panel as a main panel in the outbuilding with a ground rod(s) and tie the nuetral to the bond. No longer though.

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    • #3
      Re: New sub panel

      I do not understand are you telling me that i can not put al service wire in conduit? I was planning on running conduit,but It says it can be direct burial.

      Also what size should I run for a 100amp sub at 150'?

      thanks

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      • #4
        Re: New sub panel

        If it's direct burial cable, you don't need conduit, make sure it's buried deep enough though. As for the 100amps - that 2awg is not acceptable for sub panels. You would need to either A- Down size your breaker to a max of 90amps, probably lower for the run, or B- upsize your wire to a minimum of 1awg for the 100amps, but probably larger because of the run again, to 1/0awg. You must also have a disconnect at this other building as well. IF you were to bury the cable directly it would need to be down a minimum 24" to the top of the cable, or conduit (I'm guessing pvc) 18" to the top of the conduit, so a bit deeper...

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        • #5
          Re: New sub panel

          thanks Badabing, I am going to run conduit just incase the wire would ever need changed. and it will offer more protection. Burying it is not an issue, because we are already have to bury a water line out to the building. We will be getting a backhoe. Do you think I could get away with just putting a 80amp breaker Never plan on runinning anything else out there. Even the air compressor will only get used once in a while

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          • #6
            Re: New sub panel

            80amps should be fine. Since you are running conduit, it is much easier now to run larger conduit and cheaper, if you ever need to upsize the wire. It's also easier to pull the wire through larger pipe. I'm also not sure where you live, but if if you have frost, put expansion fittings at each end so when it freezes it doesn't pull the conduit from the house and break it.

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            • #7
              Re: New sub panel

              Originally posted by trykonxlgold75 View Post
              I need to run electric to a new out building and i just wanted to check my thinking.

              I will putting a few lights, 1or2 20amp circuit outlets, and a 30 amp 220v for an air compressor.

              I plan on running 2-2-2-4 al service wire to a panel with a main breaker (used for the disconnect) the out building is about 150' from the service panel I am pulling from. it is a 200amp service just serving a garage, lights and water heater for a 1/2 bath and an oil furnce.

              Question is with that distance is it still ok to put a 100amp breaker or should I go smaller?

              Do i need a ground rod since i am running one from the main panel?

              Is this overkill for all that we need?


              thanks
              If you buy a main breaker panel you require no other disconnect. Sure you can install a 100 amp main breaker panel, in the out building. It is only a disconnect. The breaker that feeds the sub panel must be the correct size for the wire you are using. 2-2-2-4 while compliant for a 100 amp feeder (breaker) is to small for the voltage drop (distance). You will need to increase wire size. What type of wire are you using. Tell us the letters on the jacket so we can figure the VD.

              Here is a VD calculator. http://www.liteco.ca/Portals/_Rainbo...calculator.htm

              Yes, you need a ground rod or two.
              I would use at minimum 2" PVC conduit or larger.
              Licensed Electrician

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