What is the function of the "C" wire on the Z-stat?

The "C" wire, or common wire, plays a crucial role in HVAC systems that use smart thermostats, like the Z-stat. Its primary function is to provide continuous power to the thermostat and any connected applications, allowing them to operate effectively without relying solely on batteries. This is particularly important for smart thermostats that require more power than traditional models, as they often have features such as Wi-Fi connectivity, touchscreen interfaces, or advanced monitoring functions that consume significant energy.

For systems lacking a "C" wire, users might experience performance issues or limited functionality, as the thermostat won't have a steady source of power. Thus, the "C" wire is essential for powering applications and maintaining the full range of features offered by modern thermostats.