What is the common voltage used in residential HVAC systems?

In residential HVAC systems, 24V is the common voltage predominantly used for control circuits. This lower voltage is important for safety reasons, as it minimizes the risk of electric shock during maintenance or service work. The 24V system typically powers components like thermostats, relays, and contactors that allow for the control of the heating and cooling equipment without the need for high-voltage electricity.

In contrast, while both 120V and 240V are utilized in larger HVAC components (such as the compressor and indoor blower motors), they are not used for control circuits. These higher voltages are necessary for heavy-duty operations, but the components that provide control functions are designed to operate safely at 24V. The voltage of 48V is less common and not standard in residential HVAC applications, making it an incorrect choice for typical residential systems.