Thermostats

Thermostats are devices that regulate ambient temperature by controlling heating and cooling equipment to maintain a user-set point. They compare the measured temperature with the desired setpoint and issue a control signal to activate or deactivate the connected equipment.

Sensing and types: Traditional thermostats often use a mechanical sensor such as a bimetallic element; modern models employ electronic sensors (thermistors or RTDs) and digital electronics. They can be simple mechanical, fully digital, or smart devices with network connectivity.

Controls and features: Thermostats may provide on/off control with hysteresis, or more advanced proportional, proportional-integral-derivative (PID) control. They handle single-stage or multistage heating and cooling, and in heat pump systems include changeover logic and fan control. Some models offer presets for comfort, economy, or away modes.

Wiring and installation: Most thermostats connect to HVAC systems via low-voltage wiring, using terminals such as R (power), W (heat), Y (cool), G (fan), C (common), and O/B (heat pump reversing valve). Compatibility with equipment, power requirements, and proper wiring are important during installation, and some units require a common wire for powering digital electronics.

Smart thermostats: Internet-connected models enable remote control, scheduling, energy-use reports, and integration with smart-home ecosystems. They may learn occupancy patterns, support voice assistants, and provide detailed feedback to aid energy efficiency.

Maintenance and safety: Regular calibration, battery replacement where applicable, and software updates help maintain accuracy and reliability. Proper placement away from heat sources, drafts, or direct sunlight improves sensor performance and comfort.