Today I decided to take advantage of the near 70 degree weather and started wiring up my solar system. I am still waiting on the inverter to come, but I have run the 240 line to the shed where the solar will be installed and have wired up the combiner panel and the DC shutdown switch. I went a little overboard on the wiring, I am using 10/3 for the 240 volt wiring which is rated at 30 amps. My system most likely will not push anything more than 15 amps but I decided to go this route so I can upgrade my system down the road if need be. The oversize circuit will have an added benefit of minimizing the voltage drop across the 75 feet of electrical wiring between the solar inverter and my main electrical panel. As for the DC side, I am using outdoor rated and UV resistant 10 gauge wiring. The wiring also has thick insulation designed to handle high voltage DC. The DC circuit for my panels will be running around 180 to 230 volts. Each string has the potential to operate at 6 amps and I plan to have 3 or 4 strings. The combiner panel has several safeguards. Each string is on an independent 15 amp fuse. The entire combiner box is protected by a 60 amp breaker and has surge and lightning protection modules protecting both the Positive and Negative connections for the system. Any fault current will be safely sent to ground protecting not only the system, but anyone near it. This will also prevent a fire if there is a voltage leak or fault wire.
As an additional layer of protection, my DC shutoff switch is over rated and has additional surge suppression devices. The reason for the rapid DC shutdown is to kill power to the system if their is an emergency. The inverter is designed to shutdown in the event of AC power loss as a safety measure to protect linemen from getting electrocuted while working on power lines. The inverter will also shutdown in the event of DC power loss. My system will have both AC and DC shutdown switched located on the exterior of my shed so the solar system can be completely disconnected and safely shut down.