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Thread: Micro-Inverters in the Attic

  1. #11
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    Quote Originally Posted by jaggedben View Post
    ..Roof surfaces get really hot too. The Enphase IQ7 has a max temp rating of 65C..
    Never seen equipment listings over 40c max, much less 65C, not even circuit breakers. Maybe 65C is max termination or lug rating.
    Roger Ramjet NoFixNoPay

  2. #12
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    Quote Originally Posted by jaggedben View Post
    ..The Enphase IQ7 has a max temp rating of 65C..
    Found it. Enphase IQ7/Plus.
    Ambient temperature range -40ºC to +65ºC

    Amazing. Never imagined roofs getting that hot behind a panel, in the shade.
    At 65c wire must be 150%+ oversized, per NEC Table 310.15(B)(2)(a)
    Roger Ramjet NoFixNoPay

  3. #13
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    Quote Originally Posted by ramsy View Post
    Found it. Enphase IQ7/Plus.
    Ambient temperature range -40ºC to +65ºC

    Amazing. Never imagined roofs getting that hot behind a panel, in the shade.
    At 65c wire must be 150%+ oversized, per NEC Table 310.15(B)(2)(a)
    Usually with micros one is just plugging a listed module into a listed inverter so there's no wiring subject to NEC rules. We solar guys are also used to using 10awg wire for circuit currents less than 15A.

  4. #14
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    Quote Originally Posted by jaggedben View Post
    Usually with micros one is just plugging a listed module into a listed inverter so there's no wiring subject to NEC rules. We solar guys are also used to using 10awg wire for circuit currents less than 15A.
    True, but microinverter trunk cables typically have #12 conductors.

  5. #15
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    Quote Originally Posted by ggunn View Post
    True, but microinverter trunk cables typically have #12 conductors.
    Seemingly that is still covered by the listing as well.

  6. #16
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    Quote Originally Posted by GoldDigger View Post
    You are potentially overlooking the consequences of Rapid Shutdown requirements in recent Code cycles. One advantage of micro-inverters is that the uncontrolled DC from the panels does not travel outside the array, avoiding some of the rapid shutdown requirements. Bringing the DC inside the attic may trigger those requirements and shutdown at the microinverter itself would not be sufficient.
    the micro inverters will be located within 3' of the point of entry, this is still within the array boundary limits according to 690.12(B) (1), so this means the micros can act as a rapid shutdown source. which is one of the main reasons we have decided to locate them there.

  7. #17
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    Quote Originally Posted by ggunn View Post
    Microinverters typically mount up under the module backsheet inside the frame. I don't see how you could mount modules but not modules with micros. Mounting microinverters in the attic would be, IMO, a wiring nightmare. You'd have to either have a roof penetration under every module or home runs between every module and its inverter. It's not something I would ever consider.

    Some AHJ's I deal with allow microinverter interconnections with Romex but some also require a #8 ground wire.
    the reason we are installing these in the attic is our particular system has no space at all on the roof for the inverters, its a thin film BIPV setup. A home run per string would mean around 10 pairs of armoured and labelled cables heading down to multiple string inverters which is just too uneconomical to consider. Surely loops between micro inverters in the attic is less of a nightmare than a home run from each penetration point?

  8. #18
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    Quote Originally Posted by pv_n00b View Post
    I've seen some resi roof mounting systems that won't allow MLPE boxes under the modules. They are zero clearance systems that attach the modules flat to the roof. I don't see them often because with no back of module airflow it really heats up the modules and reduces the output but they are out there. RSS will probably kill them off.

    Since you will have a lot of roof penetrations OP make sure your sealing technique is 100%. Better yet, use a string inverter.
    we have a very good design for sealing each point of entry but thank you for the concern, and as in an above reply, a string inverter is too uneconomical to consider for our particular system.

  9. #19
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    Quote Originally Posted by jaggedben View Post
    I guess if one extended the DC conductors beyond the length of the module leads then 2017 requirements could be triggered. Otherwise I see it as quite unlikely they'll be outside the array boundary. Perhaps my comment was unwarranted though; yes it could be an issue if one installed them just so.



    Roof surfaces get really hot too. The Enphase IQ7 has a max temp rating of 65C. There are a bunch of reasons I think it's a bad idea but that's not high on the list.
    you are correct, we are going to be using the IQ7+, temperature has been a heated (pun intended) discussion point around here, but we are pretty sure we have it sorted. After reading my other replies to concerns, are there any more reasons this may be a bad idea you can think of?

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