Jeff, This is a theoretical opinion, not grounded in direct experience ;^) : The well pump may indeed be causing a voltage dip due to its starting surge - wire to AC pumps has been historically sized to permit up to a 35% voltage drop at the pump at startup. Due to tight IEEE929 restrictions, that's well outside the acceptable voltage range for the inverter. But that would be likely to cause only a 5-minute line disturbance shutdown of the inverters, per UL1741.
Undersized wire is more likely to cause a voltage rise, not drop. This would be a separate issue. The wire resistance would cause the inverter's own output voltage to rise to match the grid voltage plus the effects of wire resistance, causing a voltage rise close to the additional voltage source, the inverters themselves. Your observation that each works well by itself supports this theory. Check the AC voltage at the inverters and at the mains panel to see if this might be the case. Note also that some utilities raise line voltage during times of peak load, such as summer daytime air conditioning. Notice when the shutdowns occur, and if the line voltage is higer at these times. Allan at PosE -----Original Message----- I have installed many Fronius grid-tie systems having a single inverter, but recently installed a dual 3K inverter system and are having all kinds of problems with the inverters not connecting to grid due to out-of-range grid voltage or cycle errors. If we shut down either inverter, the remaining inverter usually works fine. The only thing we can identify is the electrician may have under-sized the new feeder wiring as we had to run over 150 feet to the first breaker panel in a barn, which was another 150 or more feet to the main panel and meter base. The sub-panel also serves a large well pump that supplies several different buildings and this may be causing some voltage sags. We are looking into up-sizing the feeders, but I am still wondering if there are other issues or concerns when you have multiple inverters side-by-side at the end of a long grid connection. Thanks, Jeff Yago _______________________________________________ List sponsored by Home Power magazine [email protected] http://lists.re-wrenches.org/listinfo.cgi/re-wrenches-re-wrenches.org List rules & etiquette: http://www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
