[RE-wrenches] AFCI error on SunnyBoy

[Kirk Herander]

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.

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.

At least I know where the loose connections are / were..

 

Kirk Herander

VT Solar, LLC 

Proven PV provider since 1991

www.vermontsolarnow.com

dba Vermont Solar Engineering

NABCEPTM Inaugural Certificant

VT RE Incentive Program Partner

802.863.1202

 

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