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Wrenches, I am serving as a consultant for a homeowner with an array of solar equipment that doesn't do what he wants, a common story. He wants independence in the event of an extended utility outage. To cut to the chase: He has one array of 3,100 watts feeding through a controller into a 48V battery bank. No issues with this. A second array of 4,230 rated watts (2 9-module strings of 235W Sharp modules) currently feeds a Fronius IG-4000 inverter and the grid. In the event of an outage this system shuts down, of course. He is looking at replacing his existing pair of old SW5548s with a single Schneider XW system, or possibly a Radian. I would like to give him the ability to switch from the Fronius inverter to a 600V charge controller if either a) the grid went down or b) the Fronius failed. I looked at Morningstar's TS-MPPT-600 controller with the DC transfer switch, but its DC output is rated as limited to 60A, less than the 4.2kW output of the array. The spec sheet gives a nominal maximum wattage of 3,200W, although a note adds that "input power can exceed Nominal Maximum Operating Power, but controller will limit and provide its rated continuous maximum output current into batteries. This will not harm the controller." I looked at Schneider's XW MPPT80 controller, which has the necessary higher capacity. But beside lacking any built-in or optional input metering, it lacks the transfer switch available with the Morningstar. So questions: - Is there a good transfer switch to use with the Schneider unit, to allow manual switching of the PV input between the Fronius (when the grid is up) and the controller and batteries (when the grid is down)? - Should I use the Morningstar unit, recommending that the periodic flatlining due to the excess wattage be simply accepted as a small concession to being able to use the array during an extended outage? - Is AC coupling simply a better approach? - Any other solutions? Thanks, Allan --
Allan Sindelar |
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