I would like to confirm the idea that, for transformerless inverters, the PV grounding system's point of return (i.e. where the neutral and ground are connected) should be in the same panel where the PV system is connected. In other words, connecting the PV grounding system to the existing grounding system, if the PV system is connected to a subpanel for instance, could lead to tripping of RCDs upstream of the inverter, up to the main panel. Therefore a dedicated ground should be set up for the PV system.
Transformerless inverter grounding point
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can anyone provide me with a link or youtube video or anything related to pv grounding, especially for non-isolated inverters? -
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Start with manufacturer's recommendations, then follow Article 690 of NEC, then finally do what your AHJ (authority having jurisdiction) requires.Comment
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If the point of neutral-ground bonding is at the main breaker panel while the PV system itself is connected to a subpanel, then unwanted tripping will occur upstream. On the other hand, bonding the PV's neutral with ground at the point of connection (i.e. subpanel) will solve this issue by restricting the tripping to the PV connection. Don't you agree? Please keep in mind that I'm talking specifically about grid-tied unisolated inverters.Comment
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i'm just talking about the case where the inverter is tied to the grid at the level of a subpanel and not the main panel.Comment
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if you draw the diagram, the return path of a fault current emanating from the DC side is not clear if the neutral-ground bond is at the main panel and the connection is made at the subpanel level.Comment
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You are going to have to explain why you think connecting the PV at the sub panel or at the main panel makes any difference at all.CS6P-260P/SE3000 - http://tiny.cc/ed5ozxComment
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The return path of any fault current at the DC side of the inverter will have to pass through the main panel even if the connection is made at the subpanel for instance?Comment
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If fault current (hot to ground but not to neutral) has to go over the EGC all the way to the main panel that is just fine. It is heading for the secondary neutral terminal on the POCO transformer over the POCO neutral anyway, not to some magical "earth" ground connection.
The decision made in the NEC is that normal current should never travel over the Equipment Grounding Conductor (= EGC = ground wire). If you bond at the sub panel, then the EGC from sub to main will be in parallel with the corresponding neutral wire and will share the normal neutral current. Whether or not you want to learn more about why or have differing opinions about relative safety, that is the Code and you are not going to change that.
Whether or not the DC side of the GTI is solidly grounded at any point has no effect on this issue.
Whether or not you have a separate DC ground electrode for the racking and wire raceways has no effect on this issue.
Do not bond neutral to ground at a subpanel.
For a transformerless GTI the only driving force for DC current when some point in the array is accidentally grounded is through the AC side of the GTI and thus back to POCO. It is not an isolated DC circuit on the DC side.SunnyBoy 3000 US, 18 BP Solar 175B panels.Comment
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Does anyone fuse theirs grounds from the array to the inverters? I have a Solar Edge setup and the electrician was worried about back feed. I had only accounted for fusing the positive side of the DC using a Midnight combiner box. He added another box where he could add fusing to the ground wires from the strings. From there I had designed to feed 2 lines (6 ga 4 conductor - 100 ft run to the garage) to an external DC disconnect and then to 2 SE7600's.Comment
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