Thanks Bill. It's the "Claim Dance" that concerns me. I sent an inquiry to AEI Tech Support asking about the grounding status of the Array during operation. It was a simple question: Regarding AEI Solaron PV Systems: Is the PV array normally grounded during operation?
I would be more than happy to share the response except for the little "you might get sued" notice at the bottom of their response... <Start Quote> This message, including any attachments, may contain information that is confidential and proprietary information of <REDACTED>, Inc. The dissemination, distribution, use or copying of this message or any of its attachments is strictly prohibited without the express written consent of <REDACTED>, Inc. <End Quote> Their response is that the arrays are NOT ground referenced during operation. Specifically that the array is floating during operation. The neutral conductors are grounded when the system is not operating. This information suggests that 690.35 is in play. All of the AEI system designs that I have seen only have OCP & Disconnecting means in non-neutral conductors. How did that happen? These things have been in the field now for 3 years. How does it still keep happening? In light of the information above, do you (or anybody) still think the neutral conductors should be marked white? I am not opposed to bi-polar or floating arrays. Frankly, I believe that properly designed and installed floating arrays are inherently safer than grounded arrays. My primary concern is that some/most/all of the AEI systems going in these days may not be properly designed and installed, per 690.35. I have additional concerns around whether or not the arrays are actually operating at >600V, which would require >600V fuses, disconnects, cables, modules.... You get the picture. I have personally done some testing (on systems with inverter-integral PV tie) which indicates that the arrays are NOT operating at >600V. I have questions about whether or not my Fluke picks up actual voltage in a high-freq switched array, but I can state conclusively that I never saw voltages >600V in any portion of the arrays during operation. (Read this as "I'm less concerned about this issue than the previous") I have NOT performed these same tests on a system equipped with the Remote PV Tie, and am reserving an opinion on that until I do or someone can conclusively demonstrate that system voltage is <600V. I have followed up with a request for AEI's position on the 690.35 matter as well as their recommendation(s) for marking of the neutral conductors. I guess I will have to follow up with a request to disseminate, too. Opinions & thoughts? -Matt _____ From: Bill Brooks [mailto:[email protected]] Sent: Monday, May 03, 2010 5:17 PM To: [email protected]; 'RE-wrenches' Subject: RE: [RE-wrenches] AEI Solaron Inverters - DC Grounded or Ungrounded Matt, They claim to use a bi-polar array with 600Vdc per pole. All bipolar arrays must be grounded, so they must be grounded. They claim to be grounded through the ac service transformer while operating. They are fundamentally similar to many ungrounded designs. So, it IS grounded during operation every time the transistor closes, which is very fast, so they don't spend much time ungrounded during operation-maybe never because they are operating on 3 phases. The neutrals would have to be white. Bill. From: [email protected] [mailto:[email protected]] On Behalf Of Matt Lafferty Sent: Monday, May 03, 2010 1:28 PM To: RE Wrenches Subject: [RE-wrenches] AEI Solaron Inverters - DC Grounded or Ungrounded Wrenches, Can anyone DEFINITIVELY tell me whether the DC systems on AEI Solaron based plants is grounded or ungrounded during operation? Have you tested your theory in the field? What marking requirements do you suggest for the neutrals? Thanks! Matt Lafferty
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