NEC 2017 and RSS - I feel so blessed

 So I'm working on getting an off-grid home built in Alaska. It's not a cabin or a DIY homestead. It's a house by a custom builder that just happens to have to be off-grid. The builder builds to code, which is great, but this is their first off-grid home, so we're all learning some things as we go. One of those things is what the electrical inspectors will want to see for code compliance with regards to my PV installation. 

 Today I get word that after a meeting of the inspectors and some other knowledgeable folks within the State of Alaska including at least my electrical contractor, the inspectors have decided they are going to inspect against the 2017 NEC code as it has been adopted by the state. Yay me! 

 So as I understand it, that now requires my intended roof mounted array to include the remote disconnects within the array itself to limit voltage on the wires to less than 80V within the array. At 30 panels that's a lot of little gizmos to have to add to the system. I wager I may be one of the first in this forum to have to deal with this on a residential install. I can't say as I'm at all happy about it and I'm not sure if I can get around it with a ground mount array or whether I want to do a ground mount array. I didn't really want to before, as the roof was already there, making a great support for 30 panels  and it's already up off the ground to get a little more sun in the late fall and early spring. 

 Does anyone know if the new 2017 NEC RSS options apply equally to ground mount vs's roof mount arrays? Perhaps I'll just start with a much smaller array on the roof and then come back and add ground mount panels after the inspectors are done and gone. 

Comments

  • PhotowhitPhotowhit Posts: 4,764Solar Expert ✭✭✭✭
    Isn't this just a box at ground level that has wires from each string of panels on the roof? and a single shut off? Something like this;
    https://www.solar-electric.com/lib/wind-sun/MNdiscos_all_frontBack.pdf


    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • mcgivormcgivor Posts: 2,393Solar Expert ✭✭✭✭✭
    The changes appear to be for roof mounted arrays for fire related access, this article covers the changes. Hope this helps.  https://www.civicsolar.com/support/installer/articles/changes-article-690-nec-2017
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    900W  3 × 300W No name brand Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal as a backup system. 
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergencies and welding.
  • aksalaaksala Posts: 37Registered Users ✭✭
    @Photowhit, not any longer. That was 2014, this is 2017! It's crazy if you ask me. The code requires voltage to be kept to less than 80V on the wires within the PV array once RSS has been initiated, and wires from the array to the inverter to less than 30V within 30 seconds of RSS activation. 
  • mike95490mike95490 Posts: 8,002Solar Expert ✭✭✭✭
    There is a brand of inverter that has "Optimizers" at each panel or pair of panels, that shuts the system down when commanded.  I don't know if they work for off-grid.
    Powerfab top of pole PV mount | 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 ,

  • littleharbor2littleharbor2 Posts: 1,093Solar Expert ✭✭✭✭

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • PhotowhitPhotowhit Posts: 4,764Solar Expert ✭✭✭✭
    edited July 12 #7
    aksala said:
    @Photowhit, not any longer. That was 2014, this is 2017! It's crazy if you ask me. The code requires voltage to be kept to less than 80V on the wires within the PV array once RSS has been initiated, and wires from the array to the inverter to less than 30V within 30 seconds of RSS activation. 
    Not sue why you think a complete disconnection won't bring the voltage down to '0'.  Solar panels are a loop, is they aren't connected there is no voltage. The inverter might have some very small storage in capacitors, but pretty much instant as well. It would be 2 breakers, one for the solar array and one for a battery to the inverter. Are you saying a single switch must do both, disconnect the array and the inverter?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • BB.BB. Posts: 28,139Super Moderators, Administrators admin
    I think they want less than 80 volts on any point in the array itself when shut down (Voc=<80 volts?).

    Since it is not uncommon to have anywhere from 100 to >500 volts from series connected solar panels (central GT inverters, any >100 VDC Vpanel input charge controllers)--You are left with some hokey disconnect every two panels, or (on quick skim) all of the solar cables must be in metal conduit(?) and "master disconnect" on roof (?).

    Not sure and have not delved into the changes in new NEC...

    Probably would be nice to have a NEC 2017+ thread to discuss the details or just continue the discussion in this thread (if OK with Akasala).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • aksalaaksala Posts: 37Registered Users ✭✭
    BB. said:
    I think they want less than 80 volts on any point in the array itself when shut down (Voc=<80 volts?).

    Since it is not uncommon to have anywhere from 100 to >500 volts from series connected solar panels (central GT inverters, any >100 VDC Vpanel input charge controllers)--You are left with some hokey disconnect every two panels, or (on quick skim) all of the solar cables must be in metal conduit(?) and "master disconnect" on roof (?).

    Not sure and have not delved into the changes in new NEC...

    Probably would be nice to have a NEC 2017+ thread to discuss the details or just continue the discussion in this thread (if OK with Akasala).

    -Bill
    Exactly Bill. I wondered if I could get away with an every other panel disconnect if I absolutely have to go that route. And I have no problem if you want to rename this thread and continue. It's rather crazy since at first I was told that my GC and his Electrical Sub wanted to check with the AHJ to see what they would be looking for. That turned into, "Gee, we're not sure. We'll have a meeting to figure it out." That led to my GC telling me that they said they intend to inspect to the 2017 NEC code as adopted. 

    Fast forward to today. I get a revised quote from a vendor in Alaska which now is supposed to include the RSS equipment. Instead of addressing 2017 code, it lists a birdhouse and the related remote combiner/disconnect from Midnight. I send an email to my GC to say that is 2014 compliant, but not 2017. His response is along the lines of, well often the inspectors only go after the intent for fire and safety and he's leaving it to the Electrical Sub to see if anything additional is needed. I'm just keeping my mouth shut for now. 
  • BB.BB. Posts: 28,139Super Moderators, Administrators admin
    Generally, the inspectors cannot inspect to a code that has not been adopted by "their agency"...

    I don't know how it works in your area--But in my area inspectors are not liable for their inspections or their recommendations/requirements. And have been known to gloss over major issues (like gray market solar panels that did not have UL/NRTL markings) or even if their requirements are wrong/dangerous:

    http://forum.solar-electric.com/discussion/3375/panel-fire-question/p1
    http://midniteftp.com/forum/index.php?topic=142.0
    http://forum.solar-electric.com/discussion/9345/system-grounding/p1 (related to midnite thread)

    See if you can work with them ahead of times and get pre-approved plans (to whatever NEC code) that make sense to you and your installer.

    For my area, the best usage for the inspectors is to point out real concerns you may have with installer/materials/other issues. And let them "enforce" what you think is best with your contractors/installers.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Posts: 4,764Solar Expert ✭✭✭✭
    BB. said:
    I think they want less than 80 volts on any point in the array itself when shut down (Voc=<80 volts?).
    So they want no potential?

    Without a loop/closed circuit there is no measurable voltage.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • mcgivormcgivor Posts: 2,393Solar Expert ✭✭✭✭✭
    There's VOC on an open circuit, so any more than 2 GT panels, more or less, will exceed 80V. The problem could be solved using DC rated relays to interrupt each pair, or individual panels in a series string where the voltage exceeds 40V, thereby satisfying code requirements, it's a major PITA having to add all this complexity to what would be a relatively simple installation. Sometimes it's better to ask for forgiveness rather than permission, but understandably you wanted to adhere to current regulations. Attached is a pdf with relays designed for the purpose, Omron make quality controls equipment which I've used extensively in the trade.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    900W  3 × 300W No name brand Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal as a backup system. 
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergencies and welding.
  • aksalaaksala Posts: 37Registered Users ✭✭
    edited July 13 #13
    I found this informative video on Midnight's site. It's mostly about the 2014 rules and how to use the Birdhouse and Remote Disconnects and breakers, and it's good info. But for 2017 just fast forward to 45:20 and start watching.  :'(

    https://www.youtube.com/watch?time_continue=296&v=SSYSUerLGUU
  • Dave AngeliniDave Angelini Posts: 4,120Solar Expert ✭✭✭✭
    Having done quite a few homes in Alaska I am surprised by your problems.
    Most homes offgrid are built to code and wired for AC power. They are tested for the certificate of occupancy with a generator running.
    There is zero DC wiring except to the batteries and from the disconnect outside the building.
    As Bill said very few AHJ's are up to 2017 and for Offgrid most do not care as long your "people" did not make an issue of this.

    But, there are exceptions and you will have to do what they want and if it is really stupid and mindless, fix it later. Good Luck!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • Dave AngeliniDave Angelini Posts: 4,120Solar Expert ✭✭✭✭
    One of my solar wrench buddies had to do this below. Is your power system in non-habitable space?

     The really bad news is they are working on 2020 right now :'(   You will have to undo some what they make you do as 2017 opens new ways to lose offgrid power and you get to come home to spoiled food in your refrigerator. Yuk

    I believe there was a big improvement for off-grid systems as relates to RS
    in the 2017 NEC - the diagrams in 690.1(b) all show the PV system
    disconnect clearly now.  If you check out the diagrams you can see that
    energy storage/battery circuits, including the battery-based inverter
    whether AC or DC coupled, are outside the PV system boundary, thus not PV
    system circuits, thus not subject to RS.
     I agree with you, Ray, as a purely off-grid solar installer and
     troubleshooter. I think all that was accomplished in NEC 2017 on this issue
     is that non-habitable structures, like the common off-grid 'power shed'
     don't need 690.12 RS anymore.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • aksalaaksala Posts: 37Registered Users ✭✭
    Having done quite a few homes in Alaska I am surprised by your problems.
    Most homes offgrid are built to code and wired for AC power. They are tested for the certificate of occupancy with a generator running.
    There is zero DC wiring except to the batteries and from the disconnect outside the building.
    As Bill said very few AHJ's are up to 2017 and for Offgrid most do not care as long your "people" did not make an issue of this.

    But, there are exceptions and you will have to do what they want and if it is really stupid and mindless, fix it later. Good Luck!
     I was surprised as well Dave, and I believe it was made an issue only in that the Electrician wanted to know what the inspector is looking for. That prompted the inspector to ask for a meeting with their peers to go over the recent code revisions. Since the 2017 RSS stuff goes into effect January 2019, we may just be able to play the birdhouse game at 2014 code. This is Mat-Su borough, so if you do any future work in that borough and it's done to code, beware. 

     And FWIW, the thought had already crossed my mind that we could just wire up the 6848 and the battery bank and generator and call it good. I could then do the solar later after we occupy. 
  • Dave AngeliniDave Angelini Posts: 4,120Solar Expert ✭✭✭✭
    edited July 13 #17
    Yes or just use a generator. Whatever they want they get! Then they leave and that is a good thing also.

    I sent you a private message.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

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