What is the primary purpose of a relay in an HVAC system?

The primary purpose of a relay in an HVAC system is to provide electrical isolation. A relay acts as an electrically operated switch that allows a low-voltage signal to control a higher voltage circuit. This ability to isolate the control circuit from the power circuit is vital for ensuring the safe operation of the system. By doing so, relays can protect sensitive control components from high voltage spikes and provide a safer environment for both the equipment and the user.

In HVAC systems, relays are often used to control compressors, fans, and other components that may require higher current than the control circuit can handle. The electrical isolation provided by the relay allows for reliable operation while minimizing the risk of damage to control elements.

In contrast, the other choices do not accurately reflect the primary function of a relay. Increasing temperature, converting AC to DC, and sensing temperature are functions related to other components of the HVAC system, such as thermostats, transformers, or converters, rather than the relay itself. Thus, the correct understanding of a relay's role highlights its importance in maintaining system integrity and safety through electrical isolation.