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I'm trying to get the right info to price out my project.

I plan to install a 200 amp sub-panel in a shed with a 125 to 150 amp feeder breaker. The shed is about 180 feet away from the main panel. The main panel also has no other loads, and is on its own pole.

I was told to get triplex 4.0 direct burial wire, but I'm not sure that sounds right.

What size and type wire would be appropriate for such a project? Am I correct in assuming this sub panel will also need two grounding rods as well?

Thanks in advanced.

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I'd use a 4/0-4/0-2/0-4 Mobile Home Feeder cable for this job

Given that you aren't going to be pushing a full 200A over the cable (which'd require 250kcmil Al, since the 83% reduction in 310.15(B)(7) doesn't apply to your situation), but need a 4-wire cable as your shed is getting powered by a feeder from your service disconnect at the pole, I'd use a 4/0-4/0-2/0-4 aluminum Mobile Home Feeder cable for this job. Furthermore, while you can direct bury MHF, I'd run it in a 2" PVC conduit instead; this way, if you decide to go up to a full 200A, you can repull the wires instead of having to dig everything back up to replace it.

You are correct on the grounding rods

The good news is that you are correct that you'll need two grounding rods at the shed. A 6AWG copper grounding electrode conductor will suffice for connecting them to the shed panel's grounding bar. Note that if your shed panel doesn't come with grounding bars, you'll need to fit the appropriate grounding bars yourself in addition to using them to land your grounding wires and pulling the green bonding screw out of the panel.

TORQUE ALL LUGS TO SPEC

Last but not least, you'll want to use an inch-pound torque wrench and/or torque screwdriver to tighten the various connections to their specified/labeled tightening torques. This is required by NEC 110.14(D) in 2017 and newer NEC editions, and is a good idea anyway as it'll keep your electrical system from giving you the loose lugnut!

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  • Thanks for the great info! What cable would I need in the case that I wanted to go ahead up to full 200A? Also, would all of the same info apply over a shorter distance? I can straight shoot the cable at 140 feet, but wanted to run my cable down my road because I do a lot of digging for tree planting in other areas of my property.
    – crilly
    Apr 12, 2021 at 2:16
  • @crilly -- I wouldn't worry about distance until you got over 250-300' or so, and if you are going up to full 200A, you'd pull 3 250kcmil Al XHHW-2 wires thru the conduit with a 6AWG bare or insulated copper ground
    – ThreePhaseEel
    Apr 12, 2021 at 2:42

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