In a unit controlled by a thermostat the differential is the difference between __________.

In a unit controlled by a thermostat the differential is the difference between __________.

• A. Temperature at which the switch turns the burners on and the temperature at which the switch turns the burners off
• B. The highest and lowest temperatures reached
• C. The ambient room temperature and supply air temperature
• D. The setpoint and the actual room temperature

Answer: (A)

The differential is the temperature band that controls when the heating turns on and off. It’s the difference between the temperature at which the burner starts and the temperature at which it stops. For example, if the system turns on at 68°F and turns off at 70°F, the differential is 2°F. This hysteresis keeps the heater from cycling too rapidly and affects how closely the room follows the setpoint: a smaller differential means tighter control but more frequent cycling, while a larger differential reduces cycling but allows bigger room temperature swings. The other options don’t describe the on/off thresholds: the overall high–low swing isn’t the switch points; ambient versus supply air temperatures aren’t the control thresholds; and the setpoint versus actual temperature is the error signal, not the specific on/off difference.

The differential is the temperature band that controls when the heating turns on and off. It’s the difference between the temperature at which the burner starts and the temperature at which it stops. For example, if the system turns on at 68°F and turns off at 70°F, the differential is 2°F. This hysteresis keeps the heater from cycling too rapidly and affects how closely the room follows the setpoint: a smaller differential means tighter control but more frequent cycling, while a larger differential reduces cycling but allows bigger room temperature swings. The other options don’t describe the on/off thresholds: the overall high–low swing isn’t the switch points; ambient versus supply air temperatures aren’t the control thresholds; and the setpoint versus actual temperature is the error signal, not the specific on/off difference.