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I am doing something similar to Running Service to Outbuilding. I tried asking for clarification there, but couldn't figure out how to. Sorry to start a new Q. If there is a better way, I'd appreciate feedback for the future. Also, FYI, this is asking for details related to a broader question I asked (400 Amp service to 225 amp and 150 amp panels). Hopefully, the below reflects what I learned there :)

I have a 2 car detached garage in Washington state, across a dirt county road from the main house (50-75 feet - need to measure). I want a 70 amp feeder to it (50 amp 240v car charger, 2 garage door openers, well pump, lights, GP receptacles). I've tried to plan the best I could based on the previous post and reading NEC 2020. I'd appreciate feedback on my plans, detailed below.

I believe I need a disconnect at the garage, so I'm planning a panel with a 70A main breaker, and 3 breakers for 3 branch circuits. E.g., Eaton BRP10B100, BR270, BR250, BRP115A1CS, and BR120. I don't also need a disconnect on the outside of the garage, do I?

I plan on running wires from the main house in a 1" PVC conduit in a trench 20" deep with 2" of sand, then the conduit, then sand, then dirt back to grade. I plan on using 3 wires of 4 AWG AL XHHW-2 and one 8 AWG solid copper wire. I believe I also need an 8 AWG solid copper wire to a copper grounding rod at the garage.

Similar to the $3K+ 400 AMP Meter Combo on the other question, I plan on using a much less expensive version, the Siemens MC0816B1400RLTM. The description of this says "This 400 Amp meter-load center combination is provided with one 200 Amp main breaker that feeds an 8 space, 16 circuit interior with feed-thru lugs that can be used to feed a load center down stream." Does that mean I can add lugs downstream of the 200A breaker and have my feeder wires connected there? Or do I first need another 70A breaker installed after the 200A breaker and before the feeder wires?

Tom Getzinger
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  • One more note. On two of the XHHW-2 wires, I believe I need three bands of electrical tape on each end: one with white (for the neutral), and one with red (for the second hot? not sure of correct term). Is that right? I can get colored XHHW-2, but only in 500 or 1000' spools. – Tom Getzinger Aug 12 '20 at 16:59
  • Is the road between the house and garage public or private? If public, it may honestly be easier to get a second service placed there. You would have to deal with right-of-way permits, and locating your private utility in the pubic right-of-way whenever someone wants to dig in the vicinity. – PhilippNagel Aug 12 '20 at 17:15
  • It is a public road (county road). I originally asked about a 2nd service. That becomes costly each month, as there is a minimum monthly charge for each service. I doubt anyone would want to dig there - it's a public road, but my house is on one side, and my garage on the other. This is one of many houses built similarly on this road. With that said, I will definitely check with the county what is involved in doing this. – Tom Getzinger Aug 12 '20 at 17:20
  • Reading more, I think I need 2 AWG XHHW-2, not 4. I was looking at the 90C column. I also saw comments about going up to 1 or 1/0 for futureproofing. What conduit size do I need for 2, 1, or 1/0? – Tom Getzinger Aug 12 '20 at 17:22
  • One more question. Any requirement or even recommendation for the width of the trench? – Tom Getzinger Aug 12 '20 at 17:39
  • You do not need red tape. black, white and green are all that is required even on a 3 phase job unless a wild leg then it is required to be orange. – Ed Beal Aug 12 '20 at 17:48
  • What's the BR270 for? There's no earthly reason to replace the disconnect switch with a "100" on the handle, with a disconnect switch with a "70" on the handle. That does not help you in any way. Better to spare that money and put it into more panel spaces. – Harper - Reinstate Monica Aug 12 '20 at 18:01
  • Do you have any expectation to want to bring other utilities over there? Water? Data? – Harper - Reinstate Monica Aug 12 '20 at 18:10
  • OK so that $600 panel is a meter + dual main (once upgraded) plus mini-subpanel on one side. Come off that into the house to two subpanels. OK works for me. Shame it's so expensive, but we're all at teething pains with this new outside disconnect requirement. – Harper - Reinstate Monica Aug 12 '20 at 18:23
  • The BR270 is the main breaker in the garage. I don't believe the 100A panel comes with any breakers (is that what you meant by the 100 handle?). I could get a 100A, but then I'd definitely need beefier feeder wire, right? No need for data. Once the well goes in, water will flow across the street to the house, but that's on the opposite side of the property from the garage. – Tom Getzinger Aug 12 '20 at 19:20
  • $600 sounds way cheaper than the ~$3,500 for the Square D the other person had. And, yes, full plan is 200A to house main panel (I assume that can be main lug on the other side of the wall from this panel), and on the mini-panel, have 40A go into the house, 70A go to the garage, and 60A go to another outbuilding next to the main house (a bunk house). I'm still wondering if the outbldg feeds can just be lugs on the mini-panel (since there is a 200A breaker between them and the meter) or if I need breakers in the mini-panel and again in the outbuildings. – Tom Getzinger Aug 12 '20 at 19:21
  • To answer my own Q above, I believe I should use 1.5" Schedule 80 PVC conduit to go from the house under the road to the garage. I believe that will work for 2 or 1 AWG. Not sure on 1/0, but I probably won't go that thick. – Tom Getzinger Aug 12 '20 at 19:44
  • With further research, I think you are right, Harper, the 100A panel does come with a 100A breaker. But, if I stick with that, do I need to size the feeder wire to support 100A? I would think if I don't, I risk potentially overloading the feeder wire. Maybe not now, but if someone adds more circuits in the garage... – Tom Getzinger Aug 12 '20 at 20:07
  • @TomGetzinger -- you are correct in starting a new question btw, so there's absolutely no need to be apologetic about it :) – ThreePhaseEel Aug 12 '20 at 23:02
  • Thanks ThreePhaseEel. I just didn't want a ton of repeated info. Harper, if I go with 1 AWG AL in 1.5" conduit, I believe the 100A breaker in the garage is enough. If I wanted to limit to 70A, I could place a 70A breaker in the mini-panel. I still haven't seen an answer to whether I must have a breaker there or if the one in the garage is sufficient. If I don't hear back, I may just use lugs there. If AHJ says I need a breaker, that's an easy add. – Tom Getzinger Aug 13 '20 at 00:42

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