MidNite Solar Surge Protection Device MNSPD-300-AC. The MidNite Solar Surge Protector Device (MNSPD) is a Type 1 device per UL1449 rev3. 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. Protection for 120 VAC and 120/240 VAC circuits. Each unit has several lights and a DC unit hooked up to a DC system will power all of the indicator lights and vice versa; an AC unit hooked up to an AC system will power all of the indicator lights. If you hook a DC unit to an AC system, however, only 1 of the indicator lights will work and vice versa, but the unit will still be safe and function properly.