In heat pump systems, what feature adds extra heating by design?

• A. Thermostat Setback Mode
• B. Second Stage Of Supplemental Heat Control
• C. Passive Cooling Mode
• D. Single-Stage Cooling Only

Answer: (B)

The feature being tested is the second stage of supplemental heat control. In a heat pump, the primary heating comes from moving heat from outside to inside. When outdoor conditions are very cold, the heat pump alone can’t meet the heating demand, so auxiliary heat is added. Having a second stage means there are two levels of auxiliary heat available, allowing the system to supply more heat as needed in a controlled way. This staged approach improves comfort on colder days and avoids overshooting or excessive cycling.

Other options don’t add extra heating by design. Thermostat setback mode lowers the indoor temperature to save energy during periods like sleep or absence, which reduces, not adds, heat. Passive cooling mode focuses on cooling without active heating. Single-stage cooling only refers to the cooling function and doesn’t address adding heating capacity.