Jeff, I had this same hesitation when we first fired up our AC coupled system. When speaking with Steve at outback and he was pretty sure that the generator would put out dirty enough power that the Fronius inverter would not like it and shut down. He was correct-it goes into an error mode as soon as the geni kicks on. Once the generator shuts down the Fronius senses the frequency is back within range and resets itself. Turned out to be a simple solution and has been operating flawlessly for almost a year now.
Good luck! Mark Dickson Oasis Montana Inc. _____ From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jeff Yago Sent: Tuesday, July 28, 2009 6:55 AM To: RE-wrenches Subject: Re: [RE-wrenches] AC coupled with grid and backup generator We are completing a residential 4 kW solar system that is on the grid, but has backup battery-powered Xantrex 6 kW inverter, AC coupled Sunny-Boy inverter, and a 17 kW Kohler generator. The larger generator is to allow operation of a ground-source heat pump during winter which is not supplied from the inverter fed panel. We have added a relay cut-out for the Sunny Boy AC output to prevent over-charging the batteries during utility outage, but have some concerns about back-feeding the generator through the 100 amp 240 VAC transfer switch when the Sunny Boy thinks the grid is still up. Will the Sunny Boy try to couple to the generator like it will the inverter which will be feeding other house loads during an outage and if so, any risk? We have wired an aux. switch contact on the transfer switch to also lock out the Sunny Boy output using the same relay control as being used for high battery voltage cutout, but this is adding other issues related to needing multiple relays due to different relay coil voltages. Anyone smoked a large generator by back-feeding from inverter when the loads are reduced or shut off? Thanks, Jeff yago _____ Netscape. Just the Net You Need.
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