Which of the following is not a part of a centralized air conditioning system?

In the context of a centralized air conditioning system, a BTU, or British Thermal Unit, is not a physical component like the other options. Instead, a BTU is a measurement of energy; it is used to quantify the amount of heat energy required to raise the temperature of one pound of water by one degree Fahrenheit.

The other components—chiller, cooling tower, and air handling unit (AHU)—are integral parts of a centralized air conditioning system. A chiller is responsible for cooling the water that is circulated through the system, the cooling tower dissipates heat from the water returned from the building to maintain efficiency, and the AHU distributes conditioned air throughout the facility. Each of these components works together to provide cooling and ventilation, while the BTU serves merely as a unit of measurement to evaluate their energy output or requirements. Thus, understanding this distinction is crucial in recognizing the roles of different terminology and components within building utilities.