Monday, December 13, 2010

Wiring up the Solar Panels to the Inverter

11:55PM. I could not sleep. The racking was done and twenty-six 240 watt Phono-Solar panels were securely mounted on my roof.

All I needed to do now was bend and install the last bit of conduit from the ceiling of our attic down to the Sunny Boy inverter mounted on the back wall of the 3-car garage and pull a few lengths of 10AWG high voltage wiring through to it. I thought to myself, “It’s better to do it now and lose 2 more hours of sleep than toss and turn all night and not sleep at all.

Well, I finished at 5:15AM, just in time to get ready for my real job. 

I didn't dare connect the 500 Volt DC wires to the inverter yet. I measured the voltage of the solar array (before sun-rise) and both strings read wildly differing values. One was 45mV and the other was 85mV. True it was dark outside with only a few street lights on but I was worried that I may have wired something incorrectly. 

I didn't want to be 20 miles away at work when the sun came up and things started turning on. A daylight reading should be closer to 400 Volts and each identical string’s voltage shouldn't vary from the next by more than a few percent.

After fighting my way through a 10 hour day of staff meetings and paper work in my cubicle, with no sleep, I made it back home an hour before sunset. I tore open the inverter and measured the voltage on the wires. 442 Volts on both strings. “Yes!” Not only did I wire the panels correctly but they were both generating a voltage within the allowable range of the inverter. I still had time! 

Carefully using pliers and leather gloves, I made the final connection from the solar panels to the inverter. No sparks! So far so good. I flipped DC disconnect switch to the energized position. LED lights starting blinking as the inverter ran its self-diagnostic test.

I flipped on the A/C disconnect feeding the inverter to the grid. After a few minutes, the Sunny Boy grid-tie inverter clicked on and started generating power. 84 watts…. 78 watts…. 67 watts. It was almost sunset now but it was making real, usable power. Awesome!