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Preparing a 8.4kWh Solar System for Self Install

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  • frankiek3
    started a topic Preparing a 8.4kWh Solar System for Self Install

    Preparing a 8.4kWh Solar System for Self Install

    I'm currently gathering the materials for a 8.4kW solar system mounted on south facing house and (attached) garage roofs, with asphalt shingles. 3 strings in 11-11-8 with:
    Trina 280w panels
    UniRac SolarMount racking
    SMA Sunny Boy SB7.7-1SP-US-40 inverter

    The panels will all be mounted in landscape with vertical railing on the house rafters and horizontal on the garage. Roof slopes are 45degrees.

    Shading: 2 dormors on the house roof and also the garage roof is 2ft lower than the house roof. I'm going with SMA TS4-R-O optimizers (Tigo) on the 16 shaded panels.

    We are on 2008 NEC (PA).

    It would be easier to run PVwire down to the inverter, as I was planning on buying 3 x 50ft MC4 10awg PVwire cables, but I spec'd this in case:
    DC side: 6awg solid bare ground wire connecting to 5 groups of panels then into entry junction box, 6 x 10awg PVwire with crimped on MC4 connectors to the same entry junction box on the side of the house above the garage roof. 6 x 8awg THWN-2 in Flexible Metal Conduit through attic then into the garage down to inverter (which should have an integrated DC disconnect).

    AC side: 8-3 Romex to a MidNite Solar AC Surge Protector then down to the Main Service Breaker Box (200amp busbar with 200amp main breaker) in the house basement. 40amp breaker located at the bottom of the box (opposite side of main).
    Although digitally locked off when main is off:
    2008 NEC 705.22 Disconnect Device (6) "Capable of being locked in the open (off) position"
    So I guess I'll buy a breaker lockout for the only case of work being done on the inverter side with the main on.

    The plan is to drill up through the center of the rafters from the attic. Geocel 2300 for sealant.
    UniRac Rails: I have to cut a bit of the 8 208inch rails and cut a 240inch rail into 4 rails. For a every other rail in each, I'll drill a 7/32inch hole into the rail for the Ilsco grounding lug.

    I still have to source which perminant labels for code to purchase.

    Let me know what you think. Any input is appreciated.

    Edit: Added updated setup
    New image in my next reply.
    Old image for reference: Roof (Vertical) 2 171015220604.png
    Last edited by frankiek3; 10-19-2017, 01:42 PM. Reason: Updated setup

  • frankiek3
    replied
    I ended up getting 30 Trina TSM-295DD05A.05(II) Black/Black at $0.62/Watt for a system total of 8.85kW STC (from Tandem Solar Systems).
    I also purchased the Unirac Pro mounting to satisfy Trina's warranty.

    It has been cold here so my install is going slow.
    ​​​​​​​I'm actually cutting down my trees myself with the necessary personal protection equipment. Climbing is fun, but cutting through frozen wood isn't.

    Leave a comment:


  • frankiek3
    replied
    I bought the 10awg THWN-2 off eBay, since the big box stores only sell it with that rating in 8awg and larger.

    I also bought 100ft of 6awg solid bare wire to do the 2 runs of ground wire that will go into a NEMA 4X entry junction box (din rail with terminal blocks). One run for the garage and one run for the house, combined into one 10awg THWN-2. This plus the metallic conduit also being an EGC path seems OK, thoughts?

    I have decided on 3/4inch EMT down to the SMA inverter with grounding bushings at both ends. Rigid nonmetalic conduit RNC (PVC) for PV wire runs on the roof that wouldn't have support otherwise, a few feet here and there mostly 3/4inch but will need 1inch to the junction box from the house roof to stay under 40% fill.

    Trina hasn't gotten back to me, should I be worried buying from them?
    I think I'm going to switch to the pro version of Unirac mounting if they require the extra space.

    Leave a comment:


  • frankiek3
    replied
    Originally posted by foo1bar View Post

    What's underneath these areas of the roof?

    I would want the firemen to be able to cut a vent in the high-point of any room under the roof.
    If it's all one open space then 3 feet of difference (whether on N or S edge of the peak) is not going to matter.
    OTOH, if you have the kitchen completely under the array and it has no roofspace that's not under a solar module, I wouldn't want that.
    (why am I using kitchen as an example? Because a lot of household fires start there)


    I would think they'd have provision for midclamps like unirac, ironridge, etc.

    I'd email them saying "I need some clarification of the installation guide. I was planning to use Unirac with Unirac's grounding midclamps. Those clamps leave a .25" space between modules. On page NNN of the Trina installation guide it says you need 0.4 inch between adjacent modules. Does that mean I can't use Unirac's midclamps? Or is there a different rule for midclamps? "

    Possibly with your situation where you've got some modules offset from the others it'll be a problem for you.

    BTW You may have challenges in getting everything to be good w.r.t having the rails land in the right spot on the modules (not too close to the middle or too close to the edge) - especially with your staggered layout.

    Vented attic under the roof above the dormers, one and a half story house with the single open room upstairs being an oversized bedroom. Most of it is drywalled off for 4ft sections of vertical walls. North roof seems to be adequate.

    Thanks for your suggestions. I'll contact Trina and see what they say. If all else fails I can go with a different panel or [Edit] use pro style mid clamps for a 1inch space.

    The center group of panels will certainly be the hardest to install centered, but I believe it can be done.

    I already have the Fall Arrest equipment for installing: anchor, proper rope, harness, lanyard. I think I might go with a ladder attachment to have another person bring me the panels from the ground.

    I'm still thinking about what to use to hold the cable for gaps between the panels. Raceway or conduit for the less than 1 1/2 foot gaps.

    Edit: As most THHN/THWN cable is rated as THWN-2 only at 8 awg, I'm back to that, but I'll still go with 10 awg PV wire.
    Last edited by frankiek3; 10-19-2017, 01:55 PM. Reason: Additional info

    Leave a comment:


  • foo1bar
    replied
    Originally posted by frankiek3 View Post
    For fire safety code PA is on the 2009 IFC, before solar was introduced into the code. But I'm open to suggestions on safety. The North facing roofs have plenty of clearance. I would only be worried about the load on the sides.
    What's underneath these areas of the roof?

    I would want the firemen to be able to cut a vent in the high-point of any room under the roof.
    If it's all one open space then 3 feet of difference (whether on N or S edge of the peak) is not going to matter.
    OTOH, if you have the kitchen completely under the array and it has no roofspace that's not under a solar module, I wouldn't want that.
    (why am I using kitchen as an example? Because a lot of household fires start there)

    The Trina install guide also has a minimum of 0.4inch between panels. Unirac midclamps leave a 0.25inch minimum space, but I don't know if they can be install at 0.4inch.
    I would think they'd have provision for midclamps like unirac, ironridge, etc.

    I'd email them saying "I need some clarification of the installation guide. I was planning to use Unirac with Unirac's grounding midclamps. Those clamps leave a .25" space between modules. On page NNN of the Trina installation guide it says you need 0.4 inch between adjacent modules. Does that mean I can't use Unirac's midclamps? Or is there a different rule for midclamps? "

    Possibly with your situation where you've got some modules offset from the others it'll be a problem for you.

    BTW You may have challenges in getting everything to be good w.r.t having the rails land in the right spot on the modules (not too close to the middle or too close to the edge) - especially with your staggered layout.

    Leave a comment:


  • frankiek3
    replied
    It seems that most installers go with a solid bare 6AWG ground wire vs green jacketed 8AWG, so I guess I'll do that too.
    Last edited by frankiek3; 10-19-2017, 01:56 PM. Reason: Spelling

    Leave a comment:


  • frankiek3
    replied
    Originally posted by sensij View Post
    No clearance requirements to consider for fire safety?

    Have you found a source for 8 AWG MC4 connectors? Looks like it might be kind of overkill... 10 AWG and 12 AWG are much more common.

    The grounding for the rails sounds sketchy. Don't you need 1 lug per row, not per group? Looks like 6 or 7 lugs with the row design as shown.

    Have you verified your mounting design complies with Trina's installation instructions? On the garage roof, just 24" between rails centered in the 65" long side doesn't look like enough support, and even 32" in the house roof might be pushing it.
    Thank you for the responses.

    For fire safety code PA is on the 2009 IFC, before solar was introduced into the code. But I'm open to suggestions on safety. The North facing roofs have plenty of clearance. I would only be worried about the load on the sides.

    I did find a source for 8 AWG MC4 connectors, but I think I'll go with 10 AWG.

    The rails are all connected in each group due to the offset in top and bottom rows, but I don't mind adding more grounding.

    32.5inch is the limit between center clamped rails on the long end in the install guide. I will need horizontal rail on the garage for 8 panels.
    I have a horizontal layout clamping to the short side, also updated the house side. I think the extra 0.5inch can be accomplished with putting the L-feet in the middle of the panels.

    The Trina install guide also has a minimum of 0.4inch between panels. Unirac midclamps leave a 0.25inch minimum space, but I don't know if they can be install at 0.4inch.

    ​​​​ Roof (Vertical) 3 171017155204.png
    ​​​​​​
    Last edited by frankiek3; 10-17-2017, 03:53 PM. Reason: Update image

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  • ButchDeal
    replied
    Originally posted by sensij View Post

    The grounding for the rails sounds sketchy. Don't you need 1 lug per row, not per group? Looks like 6 or 7 lugs with the row design as shown.
    Yep every other rail needs to be grounded. Usually the rails with the optimizers are grounded and this assumes grounding clamps or webs and grounded joints are used.

    Leave a comment:


  • sensij
    replied
    No clearance requirements to consider for fire safety?

    Have you found a source for 8 AWG MC4 connectors? Looks like it might be kind of overkill... 10 AWG and 12 AWG are much more common.

    The grounding for the rails sounds sketchy. Don't you need 1 lug per row, not per group? Looks like 6 or 7 lugs with the row design as shown.

    Have you verified your mounting design complies with Trina's installation instructions? On the garage roof, just 24" between rails centered in the 65" long side doesn't look like enough support, and even 32" in the house roof might be pushing it.

    Leave a comment:

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