Situation: SMA5000TL with two strings of Rensola 260s was functioning perfectly
fine. We had to remove system for customer to repair roof after nasty hail
storm (no damage to modules). Reinstalled system and all commissioned fine.
Week later - customer calls and says Arc Fault light is on. Team goes and
believes a not fully tight wire at fuse at roof-top Soladeck fuse holder not
tight… resolved… no - one week later another call and same light.
Troubleshooting: take top module covering Soladeck roof enclosure off and check
strings individually. We open the strings at the microfuse individually
(ungrounded system, both positive and negative conductors are fused.)The string
not on seems to have a small but present small voltage that quickly bleeds down
to millivolt levels. Check all connections, briefly think that the single
removed module might be damaged but check Voc and Isc and check off as
functional. Two strings enter the DC disconnect separately and make 414 volts
+/- a very small level. But the A string bleeds off voltage approximately
10-12 volts if the voltmeter is left on the terminals for 20-30 seconds instead
of taking a quick, “point” reading.
Question: what would cause this slow bleed and could this be why I don't see
an arc fault light immediately but only have a few days?
Howard "Scot" Arey
Solar CenTex
254-300-1228
"Use the Texas Sun!"
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