What prevents an automatic-changeover thermostat from cycling back and forth between heating and cooling?

What prevents an automatic-changeover thermostat from cycling back and forth between heating and cooling?

• A. Blocking mechanism
• B. Thermal delay
• C. Circuit interlock
• D. Deadband

Answer: (D)

Deadband is the gap between the heating and cooling setpoints that keeps an automatic-changeover thermostat from switching modes every time the temperature wiggles. With two thresholds, heating turns on when the room dips below the heating setpoint and stops when it reaches that same point; cooling turns on when the temperature climbs to the cooling setpoint and stops when it drops below that point. The range between these two setpoints stays idle, so neither heating nor cooling runs, which prevents rapid on/off cycling from small fluctuations or sensor noise. A well-sized deadband avoids too much cycling (which wears equipment and can feel uncomfortable) while still letting the system respond promptly when the temperature moves out of the deadband. The other ideas don’t create this deliberate non-switching region between modes, so they don’t inherently prevent back-and-forth cycling.

Deadband is the gap between the heating and cooling setpoints that keeps an automatic-changeover thermostat from switching modes every time the temperature wiggles. With two thresholds, heating turns on when the room dips below the heating setpoint and stops when it reaches that same point; cooling turns on when the temperature climbs to the cooling setpoint and stops when it drops below that point. The range between these two setpoints stays idle, so neither heating nor cooling runs, which prevents rapid on/off cycling from small fluctuations or sensor noise. A well-sized deadband avoids too much cycling (which wears equipment and can feel uncomfortable) while still letting the system respond promptly when the temperature moves out of the deadband. The other ideas don’t create this deliberate non-switching region between modes, so they don’t inherently prevent back-and-forth cycling.