OCP Following Combiner

czars

For a grid tied system with battery backup, is over-current protection required immediately following the combiner? I can't get DC backfed from the inverter because it can't do that. However, I don't know about the batteries back feeding through the charge controller. I read NEC 2008 690.9 and I can't get a clear answer to my question. Can anyone provide a clear answer?

BB.

Re: OCP Following Combiner

You are looking at a "Hybrid GT Inverter" type setup?

The Inverter connects between the Utility Power and the Battery bank... There is no direct connection to the solar panels (like there would be for a pure GT system--Solar panels to GT inverter to Utility Power).

The panel connection is from solar panels to Solar Charge Controller to battery bank. You will have a circuit breaker near the battery in the wiring back to the solar charge controller.

And you will have circuit breakers/fuses if you have three or more parallel strings of solar panels (to prevent a shorted solar panel from being fed by two or more parallel connected solar panels).

I believe the NEC requires a DC disconnect between the solar array and the solar charge controller--but you should just follow installation instructions for the charge controller. The wiring (solar panel and run from combiner to the solar charge controller) should be rated for maximum current (Isc*1.25*1.25 as I recall).

-Bill