Sensata RP-18A 277v high sensitivity 4wire thermal protector for multi-tap ballasts
The black lead wire is always connected to the input live wire The white wire is the common which is permanently connected at the factory with all common wires The orange wire of the RP-18A is connected to the 277 Volt tap of the ballast The blue wire is then connected to the tap of the ballast which will match the input voltage Although the primary usage is 120/277V, the thermal protector inside of these units is rated up to 480 VAc