240 VOLT RESIDENTIAL WIRING

Understanding 220 and 230 Volt Wiring | DoItYourself
Wiring residential homes with 240 volts is a necessity, for powering some heating and cooling equipment as well as some large appliances. The 220-volt circuits as they were known prior to the 1960s are now commonly known as 240-volt circuits as 110-volt circuits are now 120-volt circuits.Author: Justin Daddio
Understanding 220 or 240 volt Electrical Circuits
This is why 240 volt circuits connect to double pole breakers that are essentially two single pole breakers tied together. In the main panel, every other breaker is out of phase with the adjoining breakers. So, in essence 240 volt wiring is powered by 2 - 120 volt hot wires that are 180 degrees out of phase.