[RE-wrenches] Interesting question

Jason Lombard openhandsolar at gmail.com
Mon Feb 9 12:36:52 PST 2009


This is from an installer in St Croix about and issue he had. Any thoughts?

                I have a client w/ an older solar array. They are at least
as old as 1991, and I installed 1 new panel and new SW4048 and L-16 bats in
Jan 2000. The 24 modules are Solarex "SX 110" but they have a 2.1 Isc and
 they measure 17.5" x 42 " each  I believe they are @ 35W each.  They are
wired 4 modules  in series , 6panels@ 48V nom.  w/ 2 panels parallel in J
box on roof w/no fuse, or diode.  3 pos

power leads go down to SQ D fused Disconnect (3, 10A FLNR fuses).

After opening PV disconnect at array site,  and measuring Voc on each input
terminal (@ 75Voc each) I measured Isc . I got 3.9 on West, 1.9 in middle,
and 3.9 on east. After I had finished w/this measure, I Heard a loud pop,
and when we inspected array found 1 panel w/cracked glass and an electrical
blow out on underneath on back sheet of module.

This was the East panel, and measuring Isc on all again, got 3.9 West, 1.9
Mid, and 1.9 Isc East.

I did not wire the array, though I did rewire the j box w.new busses.
Interestingly, each 48 V panel has 2 Pos wires, each measuring 75 Voc .;
 i.e. each output circuit (to 10A fuse) has 4 Pos wires coming into it.
Though I did not confirm w/isc test, I imagine that 2 wires were used for
Pos on each 48 V panel. There are also a total of 4 –ve wires for ea panel
as well, all –ve on 1 buss.

All panels were in direct sun when this blowout event occurred.  Also, all
modules had severe darkening of cells.

Care to  comment on this, what happened and why?


-- 
Jason Lombard
Open Hand Solar LLC.
Certified Sustainable Building Adviser
www.openhandsolar.com
505 795 8646

"I'd put my money on solar energy… I hope we don't have to wait 'til oil and
coal run out before we tackle that."

—Thomas Edison
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