Unlike a double-pole breaker, which serves a single 240-volt circuit, a tandem serves two 120-volt circuits; it cannot be used to supply 240 volts to a single circuit.

A tandem circuit breaker, also known as a double pole circuit breaker, takes up the space of a single circuit breaker on a Square D panelboard. By hominspector February 28, 2012 at 3:46AM ...