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Thread: J box and combiner

  1. #1
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    J box and combiner

    Attached pdf I have the following questions:

    1. Does the j box for each String require overcurrent protection?
    2. Does their need to be combiner or can the feeder cables from each panel go straight into inverter?
    3. Does pv source circuit in this case would be from String 1 to inverter, String 2 to inverter and their is no pv output circuit? If not then where would pv source circuit be and pv output circuit be?
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  2. #2
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    see: https://www.solaredge.com/sites/defa...gn_and_nec.pdf

    wherein on page 5
    Over Current Devices The SolarEdge power optimizers include automatic reverse current protection which prevents current from flowing from the inverter input circuit back into the PV module. The majority of SolarEdge systems may be installed with only two strings. In a two string configuration there are no other parallel connected sources of fault current between the module and the power optimizers so no overcurrent devices are required in accordance with 690.9 (A) exception a. For systems with three strings or more fuses may need to be installed in both the positive and negative conductors as required by Article 690.35(B). For more information refer to the Technical Note “String Fusing Requirements in SolarEdge Systems” in the following link: http://www.solaredge.com/files/pdfs/...quirements.pdf.

    But the above following link has 3-string illustrations without OCP.

  3. #3
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    Quote Originally Posted by BillK-AZ View Post
    see: https://www.solaredge.com/sites/defa...gn_and_nec.pdf

    wherein on page 5
    Over Current Devices The SolarEdge power optimizers include automatic reverse current protection which prevents current from flowing from the inverter input circuit back into the PV module. The majority of SolarEdge systems may be installed with only two strings. In a two string configuration there are no other parallel connected sources of fault current between the module and the power optimizers so no overcurrent devices are required in accordance with 690.9 (A) exception a. For systems with three strings or more fuses may need to be installed in both the positive and negative conductors as required by Article 690.35(B). For more information refer to the Technical Note “String Fusing Requirements in SolarEdge Systems” in the following link: http://www.solaredge.com/files/pdfs/...quirements.pdf.

    But the above following link has 3-string illustrations without OCP.
    In the pdf their is no combiner. All wires go to junction box and then to the inverter. Question #2 is their need for combiner or inverter takes care of that?

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  4. #4
    Join Date
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    Quote Originally Posted by codequestion View Post
    Attached pdf I have the following questions:

    1. Does the j box for each String require overcurrent protection?
    A j-box is just the place where the PV wire is spliced to the THWN that's run inside conduit. If overcurrent protection is required, it could be with a fused combiner that goes in place of the J-box, or it could be with a fused combiner on the ground next to the inverter.

    2. Does their need to be combiner or can the feeder cables from each panel go straight into inverter?
    Debatable, and it depends what code cycle is being enforced. Read the second link Bill posted, it really addresses the issues in detail.
    I'll add: the 2014 NEC doesn't address optimizers at all and some AHJs may interpret the strings as source circuits and require fusing. 2017 NEC defines the optimizer string outputs as 'DC-to-DC Converters', and you may be able to avoid fusing based on new wording in 690.9, but it's not crystal clear. In practice, fusing serves no real purpose in this SolarEdge system, because the optimizers effectively prevent overcurrent faults.

    There are no 'feeders' involved here, btw.

    3. Does pv source circuit in this case would be from String 1 to inverter, String 2 to inverter and their is no pv output circuit? If not then where would pv source circuit be and pv output circuit be?
    Strictly speaking, the pv source circuits are between each module and its optimizer. There is no PV output circuit in this system.

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