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Advice: About to run conduit in slab for main power + solar

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  • Advice: About to run conduit in slab for main power + solar

    I'm about to run conduit into my new build house which will be slab on grade. We will be adding solar, so wondering what you guys would recommend running for extra conduit under the slab into the utility room? This is just for a grid-tie system with the meter at a pole about 200ft from the house underground into the utility room. This is in Maine so its not a double meter.

    I might also run a generator feed someday as well? so any recommendation for a number of conduits and size from outside to the utility room?

    Thanks!

  • #2
    I'd use at least 1" conduit for the solar DC feed, or larger. But you don't want to create a weak spot in the slab.

    Whatever size generator you plan on , use conduit that can handle 2x the expected power of the generator in case you ever upsize it.

    Will you have a dedicated battery / electrical utility room ? insure your generator will be able to directly feed your house for the time the main inverter is down for replacement, plan for a transfer switch that does not rely on the inverters internal transfer switch.
    Last edited by Mike90250; 01-22-2020, 06:53 PM.
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

    Comment


    • #3
      Originally posted by keaton85 View Post
      We will be adding solar, so wondering what you guys would recommend running for extra conduit under the slab into the utility room?
      ...
      I might also run a generator feed someday as well? so any recommendation for a number of conduits and size from outside to the utility room?
      Will you have a main breaker panel and multiple sub-panels?
      Where will those be?

      Where will the inverters be located?

      I would put in a 2" conduit from the inverter location to the main breaker panel.
      I would put in a 2" conduit from the potential generator location to the main breaker panel.
      I would put in a 3/4" conduit from the utility room to the inverter location (for CAT5)
      I would put in a 3/4" conduit from the utility room to near each of the 4 corners of the house (for CAT5 and/or RG6 (TV cable))
      I would put in 3/4" conduits to each wall in the living room (maybe multiple per wall for a larger room. They can be used for CAT5 and/or home theater speaker system.)
      I would put in a pair of 3/4" conduits to the spots that are likely spots to mount a TV (one for power, one for low-voltage cables like RG6 or CAT5 or HDMI)

      And if you'll have multiple breaker panels, I would put in 2" conduits between them. And possibly look at having your breaker panels be "Must be supported by generator" and "don't need if running off generator" - that will probably make installing generator later easier. Or plan for having space that you can add a second breaker panel next to your main one that will be "these circuits supported by generator when needed".

      For the 3/4" low-voltage wiring conduits, I think PVC would work well enough. Even smurf tube would work - but I'd probably do larger (1.5"?") smurf tube (ENT) in that case

      If possible, I'd also run CAT5 and RG6 to each room while it's still studs, and leave the conduits for future-proofing

      Comment


      • #4
        Originally posted by Mike90250 View Post
        I'd use at least 1" conduit for the solar DC feed, or larger. But you don't want to create a weak spot in then slab.
        I agree you don't want to create a weak spot in the slab. So make sure you get your plans in place and you have a good guy reviewing the slab pre-pour so they can make sure it'll be all-good.

        I didn't put anything for conduit from inverter to the roof - so I would plan on a 1" or 2" conduit from the inverter location to a spot that can be used to service the south face of the roof (and that conduit may need to be metal ( EMT or rigid)).
        It may be easier for the conduit to just go up inside the north wall (where the inverter is located) and then curve to follow the roofline, rather than have it in the slab. (of course this depends on how much space you'll have to make that curve. So if you have a thicker wall (ex. 2x10 for lots of insulation in maine) and a thicker roof rafter - and a thicker ceiling joist, and a steeper roof angle you would have plenty of space to make that curve)
        If it won't be easy to go up the wall, then plan for the DC wires to be in conduit in the slab from the inverter location to where they can go up into the attic and out the roof.

        Comment


        • #5
          Wow, Thanks guys!!! lots of great info.

          So this is a small house, only 20X38 so media and ethernet will not by something that is needed. No phone cables, just one or two ethernet drops for APs (inside and outside), although I have not decided to do ethernet/fiber to the outbuilding or just AP to AP. Anyway, this was about solar haha.

          I forget to say this will be grid-tie, with a generator planned and I am in the process of building a 18650 powerwall, although a long way off with only a little over a thousand cells.

          So consenses is lots of 2" conduit in multiple directions to safe guard future plans!

          Comment


          • #6
            Originally posted by keaton85 View Post
            So this is a small house, only 20X38 so media and ethernet will not by something that is needed. No phone cables, just one or two ethernet drops for APs (inside and outside), although I have not decided to do ethernet/fiber to the outbuilding or just AP to AP. Anyway, this was about solar haha.
            JMHO - but ethernet to the outbuilding - and a conduit alongside it. Make that 2 conduits, a 3/4" size for low-voltage, and a 2" for power.

            IMO 20x38 is more than big enough for a media setup and to have ethernet to multiple spots. Even if you don't plan on using it, it may be a good thing for future use of the house as a airBnB or for future sale of the property.

            Comment


            • #7
              Originally posted by keaton85 View Post
              ......

              I forget to say this will be grid-tie, with a generator planned and I am in the process of building a 18650 powerwall, although a long way off with only a little over a thousand cells.

              ....
              I just cringe at the thought of 2 thousand un-reliable power interconnections in your cells. I frankly don't understand how tesla does it with their cars, but that's what robots are for.
              Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
              || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
              || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

              solar: http://tinyurl.com/LMR-Solar
              gen: http://tinyurl.com/LMR-Lister

              Comment


              • #8
                All that conduit under thru a slab sounds like a nightmare. What kind of building is this? Is it a log cabin, ranch, 1
                or 2 story?

                if the meter is remote, you likely will need a disconnect close by. I would check with the utility on the netmeter - is it a 2nd meter also nearby?

                How big is the solar array going to be?
                I would stay away from anything Tesla.

                Comment

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