What does hysteresis refer to in thermostatic controls?

What does hysteresis refer to in thermostatic controls?

• A. The time delay in system startup
• B. The difference in temperature setpoints for cycling
• C. The cooling load requirement
• D. The maximum temperature limit for safety

Answer: (B)

Hysteresis in thermostatic controls refers to the difference in temperature setpoints for cycling, which plays a crucial role in maintaining stable operation of HVAC systems. This phenomenon occurs when a temperature sensor, such as a thermostat, has two different threshold points: one for turning the heating or cooling system on and another for turning it off. For example, if a thermostat is set to activate the heating system at 68°F, it may turn off the heating at a slightly higher temperature, like 70°F. This range of temperatures creates a buffer, preventing the system from turning on and off too frequently, which could lead to wear and inefficiency. The use of hysteresis allows for more consistent temperature control within a space, making it essential for the efficiency and longevity of HVAC systems. In contrast, the other choices describe different concepts. The time delay in system startup primarily refers to the delay mechanisms that prevent immediate cycling to ensure operational stability. The cooling load requirement is associated with the demand placed on an HVAC system to achieve desired temperatures. The maximum temperature limit for safety pertains to the protections against overheating, but it does not describe how a thermostat cycles based on setpoints.

Hysteresis in thermostatic controls refers to the difference in temperature setpoints for cycling, which plays a crucial role in maintaining stable operation of HVAC systems. This phenomenon occurs when a temperature sensor, such as a thermostat, has two different threshold points: one for turning the heating or cooling system on and another for turning it off.

For example, if a thermostat is set to activate the heating system at 68°F, it may turn off the heating at a slightly higher temperature, like 70°F. This range of temperatures creates a buffer, preventing the system from turning on and off too frequently, which could lead to wear and inefficiency. The use of hysteresis allows for more consistent temperature control within a space, making it essential for the efficiency and longevity of HVAC systems.

In contrast, the other choices describe different concepts. The time delay in system startup primarily refers to the delay mechanisms that prevent immediate cycling to ensure operational stability. The cooling load requirement is associated with the demand placed on an HVAC system to achieve desired temperatures. The maximum temperature limit for safety pertains to the protections against overheating, but it does not describe how a thermostat cycles based on setpoints.