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2. Thermostat - Wikipedia

   en.wikipedia.org/wiki/Thermostat

   The reversing valve, controlled by the thermostat, causes the change-over from heat to cool. Residential heat pump thermostats generally have an "O" terminal to energize the reversing valve in cooling. Some residential and many commercial heat pump thermostats use a "B" terminal to energize the reversing valve in heating.

3. Heating, ventilation, and air conditioning - Wikipedia

   en.wikipedia.org/wiki/Heating,_ventilation,_and...

   Electrical heaters are often used as backup or supplemental heat for heat pump systems. The heat pump gained popularity in the 1950s in Japan and the United States. [14] Heat pumps can extract heat from various sources, such as environmental air, exhaust air from a building, or from the ground. Heat pumps transfer heat from outside the ...

4. Freeze stat - Wikipedia

   en.wikipedia.org/wiki/Freeze_stat

   Air coil freeze stat. A freeze stat is a temperature sensing device for HVAC that monitors a heat exchanger to prevent its coils from freezing.Freeze stats can be used on both refrigerant-to-air, and refrigerant-to-liquid type heat exchangers and serve different purposes with similar goals for each.

5. Reversing valve - Wikipedia

   en.wikipedia.org/wiki/Reversing_valve

   A reversing valve removed from an HVAC heat pump for replacement. A reversing valve is a type of valve and is a component in a heat pump, that changes the direction of refrigerant flow. By reversing the flow of refrigerant, the heat pump refrigeration cycle is changed from cooling to heating or vice versa. This allows a residence or facility to ...

6. Thermal expansion valve - Wikipedia

   en.wikipedia.org/wiki/Thermal_expansion_valve

   A thermal expansion valve is a key element to a heat pump; this is the cycle that makes air conditioning, or air cooling, possible. A basic refrigeration cycle consists of four major elements: a compressor, a condenser, a metering device and an evaporator. As a refrigerant passes through a circuit containing these four elements, air ...

7. BACnet - Wikipedia

   en.wikipedia.org/wiki/BACnet

   BACnet is a communication protocol for building automation and control (BAC) networks that use the ASHRAE, ANSI, and ISO 16484-5 standards [1] protocol.. BACnet was designed to allow communication of building automation and control systems for applications such as heating, ventilating, and air-conditioning control (), lighting control, access control, and fire detection systems and their ...