[RE-wrenches] DC Series Fusing in inverters

[Jason Szumlanski]

SMA inverters typically come with 15A KLKD fuses pre-installed. I have seen
a bunch of blown fuses recently (after cold weather)... It seems that some
dealers are just assuming the 15A fuse is okay for series strings and not
doing the calculations. I've been finding quite a few Evergreen systems or
parallel connected two-string SunPower systems that should have 20A fuses
per NEC 690.8. The problem does seem to be worse where inverters are
exposed to direct sunlight, presumably from fuses that no longer meet their
ampacity rating due to heat.

Anyone else run into this frequently?

Jason Szumlanski
Fafco Solar
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