Phil,
NEC 690.17 says "Where all terminals of the disconnecting means may be
energized..." It would take a pretty rare malfunction of a grid
connected inverter to energize the load terminals of the utility
disconnect. But we have some AHJs that require this label on every ac
disconnect, all the way back to the utility meter, anyway. The warning
is appropriate on the dc disconnect of almost all inverters because the
capacitors in the inverter take a few minutes to bleed off.
To me, the bigger hassle are plaques required by 705.10. Can anyone
give me a reasonable explanation for their value in a utility
interactive system? I can understand if there is a grid backup system -
emergency personnel may need to know where to turn off the backup power;
but a grid interactive inverter shuts down when there service is shut
down. It seems to me that this plaque is likely to send an emergency
responder on a wild goose chase.
Kent Osterberg
Blue Mountain Solar
Phil Schneider wrote:
Wrenches,
Our utilities require an external AC disconnect between the inverter and the
point of interconnection, located next to the meter. In the past, we have
marked this switch with the language in 690.17 (although no AHJ or utility
has required it). Because we generally argue against the necessity of this
switch, I don't feel it is accurate to say that "terminals on both the line
AND load sides may be energized in the open position".
Do other Wrenches post this plaque? Is there a way that both line AND load
terminals of this switch could be energized? (other than an inverter not
paying attention to its UL listing?)
Thanks again for your thoughts,
P.
Phil Schneider
Creative Energies
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