What is the primary purpose of the thermostat sub-base?

• A. Sub-base
• B. Battery housing
• C. Mounts the thermostat
• D. Display screen

Answer: (C)

The thermostat sub-base serves as the mounting interface for the thermostat, while also housing the wiring connections. It’s the wall plate that is fixed in place, and the thermostat body snaps or screws onto this base, using the terminal block on the base to receive the control wires from the HVAC system. This setup provides a stable, accessible point to secure the thermostat and route power and signal wiring, which is essential for proper operation. It isn’t the battery housing or the display screen—the battery housing is only for battery-powered models, and the display is part of the thermostat itself. So the main idea is that the sub-base mounts the thermostat and provides the wiring connections.