To prevent excessively rapid cycling of the equipment when the temperature is near the setpoint, a thermostat can include some hysteresis. The rate at which the target system temperature can change is determined both by the capacity of the heating or cooling equipment to respectively add or remove heat to or from a target system and the capacity of the target system to store heat. Increasing the difference between the thermostat setting and the desired temperature therefore does not change the time to achieve the desired temperature.
Instead, the heating or cooling equipment runs at full capacity until the set temperature is reached, then shuts off. A thermostat is an example of a " bang-bang controller" as the heating or cooling equipment output is not proportional to the difference between actual temperature and the temperature setpoint. Electronic thermostats, instead, use a thermistor or other semiconductor sensor that requires amplification and processing to control the heating or cooling equipment. In one form, the mechanical thermostat, a bimetallic strip in the form of a coil directly operates electrical contacts that control the heating or cooling source.
Thermostats use different types of sensors to measure the temperature. Examples include building heating, central heating, and air conditioners, kitchen equipment such as ovens and refrigerators, and medical and scientific incubators. Thermostats are used in any device or system that heats or cools to a setpoint temperature. A thermostat can often be the main control unit for a heating or cooling system, in applications ranging from ambient air control to automotive coolant control. 8.2 Combination heating/cooling regulationĪ thermostat exerts control by switching heating or cooling devices on or off, or by regulating the flow of a heat transfer fluid as needed, to maintain the correct temperature.8.1 Ignition sequences in modern conventional systems.6.1.1 Contact configuration nomenclature.6 Electrical and analog electronic thermostats.5.2.2 Shower and other hot water controls.The word thermostat is derived from the Greek words θερμός thermos, "hot" and στατός statos, "standing, stationary". Sometimes a thermostat combines both the sensing and control action elements of a controlled system, such as in an automotive thermostat. Ī thermostat operates as a "closed loop" control device, as it seeks to reduce the error between the desired and measured temperatures. Thermostatically controlled loads comprise roughly 50% of the overall electricity demand in the United States. In scientific literature, these devices are often broadly classified as thermostatically controlled loads (TCLs). Thermostats are used in any device or system that heats or cools to a setpoint temperature, examples include building heating, central heating, air conditioners, HVAC systems, water heaters, as well as kitchen equipment including ovens and refrigerators and medical and scientific incubators. Future research directions are also proposed to fill the identified gaps.A Honeywell electronic thermostat in a retail storeĪ thermostat is a regulating device component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint. Finally, research gaps in this field are discussed from different aspects, including performance evaluation metrics, control methods, occupancy models and buildings types. The present article aims to review the research works concerning occupancy-based control systems, classify them based on the integration of occupancy information with control systems and identify their strengths and limitations. To provide a trade-off between these conflicting objectives, a variety of occupancy-based control strategies have been proposed in the literature.
This adjustment aims to minimize the energy consumption of HVAC systems while maintaining an acceptable level of thermal comfort and indoor air quality.
These buildings can utilize current and historical data, collected from occupancy detection and monitoring networks, to predict occupancy profiles and adjust heating, ventilating, and air conditioning (HVAC) operations accordingly. Intelligent buildings have drawn considerable attention due to rapid progress in communication and information technologies.