Installation Questions

Hello--this is the roof that will support 32 LG 330W panels with the integrated Enphase IQ6+ microinverters. I'll use S5 clamps plus railing to put the panels in portrait mode. I am going to use three strings(11+11+10 perhaps) and take those wires to a junction box in the upper row of the array(have any recommendation for a decent junction box that could fit under/attach to the railing?). I wanted to run conduit through the house to the area you see with the red circle. I would take the three circuits down the conduit, to the basement, back out to the outdoor wall to an Enphase IQ combiner box, then a single set of wires to a disconnect, then back into the house to the main panel. Grounding for the racking would be via bonding the panels, ground wire and lug across the railings, then down the side of the house to the ground rod in the ground. I know I don't really want to bring the ground for the racking into the house with the wiring for the 3 strings. Does this all sound reasonable? I appreciate any and all tips and comments.

Thanks

Kevin

Comments

  • BB.BB. Super Moderators, Administrators Posts: 30,637 admin

    Welcome to the forum Kevin.

    First question is shading? I don't know the time/season of your photo--But any shading on a solar electric panel pretty much kills its output (Enphase, because they are per panel, don't have as bad of shading issue as central inverters where shading one or two panels can "kill" the entire output of a series string.

    And trees go/leaf out in spring through fall...

    Second, do you know what version of the NEC your local uses? Newest versions of NEC have lots of roof "no solar" requirements so that fire personnel can have walkways and access to the roof surface for ventilation (if you, heaven forbid, ever have a fire).

    And have you looked at the billing rules for GT Solar for your utility? In a fair number of locations now, the rate plans are starting to be biased against GT Solar (lower payments for energy you generate, may even need a separate GT solar meter in a few locations), high(er) monthly connect fees, etc.

    If you have lots of little critters that like to chew, metal conduit and screening around the array to keep them from nesting underneath...

    Running the ground wire down the th outside of the house (suggest 6 AWG minimum, or use actual ground braid for lightning control systems--If you are in a lightning prone area).

    If the array runs from "one side of the home to the other", then you probably want ground rods (and cabling) down the opposite sides of the array.

    And, the lightning ground rods need to be bonded (6 AWG minimum again suggested--Review your NEC code for details/requirements) back to the main ground rod/system/green wire/neutral bonding for your main panel (lots of distributed ground is good for lightning. Having one ground wire to connect the array frame to your main panel ground required so that if there is a short circuit somewhere, the AC fault current can trip a breaker in your main panel/prevent the metal work from becoming hot and an electrocution hazard).

    And if you have lightning in your area, adding good quality surge suppressors on your AC main panel, and ideally in at a J-Box where your AC runs on the roof enter your home), is a good idea too.

    https://www.solar-electric.com/residential/circuit-protection/surge-protection.html

    Mfg's documentation:

    http://www.midnitesolar.com/pages/spd/spd_documents.php?productCat_ID=23&productCatName=Surge%20Protection%20Devices&model=MNSPD-300-AC&product_ID=601&act=products

    http://www.midnitesolar.com/pages/spd/videos.php

    My suggestion is to make sure you GT solar actually saves/makes money for you. In the decades past, the rate plans favored the GT Solar owner. In present times, and as we head into the future, the rate plan GT Solar subsidies are slowly going away (and in some places like Hawaii, Nevada, and parts of Canada), GT Solar has either been disallowed, or has become financially not-viable.

    Looks like you may be still under construction--Conservation is generally your best bet for "investing" your money. It is almost always cheaper to conserve than to generate power (lots of insulation, mini-split heat pumps, Energy Star rated appliances, using laptops vs desktop computers, etc.).

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • FatawanFatawan Solar Expert Posts: 71 ✭✭✭

    Hi Bill

    Shading--it's a mountain lot, so different amounts of shading at different times of the year, but good sun after midmorning year round.

    Code--we are years behind. I think 2012 or so. I am not certain of that, but it is many years behind. I recall looking up the rules on having a walkway for firemen and we did not fall under those rules because that roof is only a 2:12 pitch. At that pitch, we could go edge to edge.

    Ground--Where the ground wire/braid will come down will be right at the main panel ground rod

    Surge protection--good idea

    Building a super efficient house(staggered stud walls, triple pane windows, best heat pump, etc.). The utility here in my state is promoting solar, giving us a $.60/watt rebate upon installation. It's a net metering state, so we reset the clock once per year on our output that has gone back into the grid. With the federal tax credit also in the mix, it makes a lot of financial sense.

  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭

    If you get snow there, you may also want to pre-install fall protection anchor points. They may be handy for installation purposes, and metal roofs can be really tricky if you need to clear snow, bird bombs, etc.

    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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