The only time you can have a Class 2 circuit is when the power source for the circuit origniates from a listed Class 2 power supply. Class 2 circuits can be in conduit, but not along with power or Class 1 circuits.Class 2 Circuit. The portion of the wiring system between the load side of a Class 2 power source and the connected equipment. Due to its power limitations, a Class 2 circuit considers safety from a fire initiation standpoint and provides acceptable protection from electric shock.