Midnite Solar MNSPD-300-DC 300V Dc Surge Protector Device The MidNite Solar Surge Protector Device (MNSPD) is a Type 1 device per UL1449 rev3, it has an outdoor rating of 4X for outdoor use. It is designed for both AC and DC systems and provides protection to service panels, load centers or where the SPD is directly connected to the electronic device requiring protection. The DC SPD will work well on all DC circuits up to 300 volts as well as any 120/240 VAC circuits. The difference between the AC and DC SPD is the way the LED's are powered. The protection side of things is identical. Protection is achieved by reducing the clamping voltage to a safe level that your system can sustain and that won't damage electronic components. Listed by ETL for US and Canada, made in the USA.