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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:14.0pt'>I was called to do an evaluation of a SB / SI AC-coupled system installed by others. One of the 4 SB’s(9000watt TL) had a hard arc fault error which could not be reset. Apparently a fault since commissioning (sic).After checking all visible connections, I isolated each one of three sub-arrays feeding this inverter’s combiner. With only sub-array 1 connected (fuse holders closed) the inverter powered up normally. So I opened up 1 (and 3) and closed circuit 2 fuses. Open circuit voltage OK. I powered up the inverter and immediately heard a loud pop. One of the interconnects in that sub-array literally blew apart and opened up. So I isolated arrays 1 and 2 and tried 3 alone. Same thing, vaporization of an interconnect. FYI – no fuses were blown on either defective circuit, but I guess that’s not surprising in this scenario.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'>So the inverter operates fine and only “good” sub-array is #1. I’m curious as to why when all three sub-arrays were combined, there was not a meltdown of 2 & 3 connections before the AFCI error shut the inverter down, but individually the faulty circuits were not caught by the AFCI circuit before the damage occurred. Thoughts anyone? Thanks.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'>At least I know where the loose connections are / were……<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'><o:p> </o:p></span></p><p class=MsoNormal><b><span style='font-size:14.0pt'>Kirk Herander<o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:14.0pt'>VT Solar, LLC <o:p></o:p></span></b></p><p class=MsoNormal><b><i><span style='font-size:14.0pt'>Proven PV provider since 1991<o:p></o:p></span></i></b></p><p class=MsoNormal><b><span style='font-size:14.0pt'><a href="www.vermontsolarnow.com">www.vermontsolarnow.com</a><o:p></o:p></span></b></p><p class=MsoNormal><span style='font-size:14.0pt'>dba Vermont Solar Engineering<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'>NABCEP<sup>TM </sup>Inaugural Certificant<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'>VT RE Incentive Program Partner<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'>802.863.1202<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>