Quote:
Originally Posted by virginiajim
I have a problem with the PV attachment upstream of the transfer switch so it stays connected to the grid when the grid goes down. Doesn't this allow the PV's to feed (backfeed) the dead grid which energizes it and poses a problem for anyone working on it?
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NO! If the inverter is attached to the "dead" grid side of the transfer switch, and the inverter is a grid-tie UL 1741 approved inverter, then the inverter will remain inactive until the grid comes back online and the grid STAYS online for a period of time. In the case of my Enphase microinverters, that period is ~5 minutes of stable 60hz with voltages inside a set range. If either the frequency, or the voltage goes out of range, the 5 minute timer resets and doesn't start counting down again until the out of range issue is resolved. UL 1741 approved inverters require NO human interaction to shut them down when the grid goes down. They shut down automatically in fractions of a second. It is sometimes referred to as "Anti-islanding". You can use your favorite search engine with the "UL 1741 and Anti-Islanding" to read about this feature.