Surge Protective Device Selection Guide
SPDs need to be sized correctly. If they are sized too low, the system could be susceptible to temporary overvoltages. It can also decrease the SPD life expectancy. If they are sized too high, it could be damaging to equipment.
To determine which SPD size should be used for the system, you must know the reference to ground as well as the type of voltage that is present. The formula to use depends on the type of system.
This calculator will determine an optimal MCOV size for your specific system.