A Comprehensive List of Commonly Used Technical Terms in HVAC Systems
HVAC is an abbreviation for Heating, Ventilation, and Air Conditioning, widely used in the field of building environmental control. The following is a compilation of core industry terms and standard definitions, categorized by system module, covering commonly used terms across design, equipment, operation, commissioning, and maintenance.
I. Core Basic Definitions of Class Nouns
1. Heating : A system that uses artificial equipment to deliver heat into a room to compensate for heat loss and maintain a set indoor temperature. It is divided into centralized heating, localized heating, and other forms.
2. Ventilation : The process of replacing indoor and outdoor air through natural or mechanical means, expelling polluted, humid, and harmful gases, and introducing fresh air to improve indoor air quality. It is divided into natural ventilation and mechanical ventilation.
3. Air Conditioning : also known as air conditioning, is a technology that artificially controls parameters such as temperature, humidity, cleanliness, wind speed, and pressure of indoor air to make the indoor environment meet the requirements of production, living, comfort, or process.
4. Heat load : The amount of heat that needs to be added to the room to maintain the indoor design temperature in winter is a core parameter for selecting heating equipment and designing the system.
5. Cooling load : The total heat gained from indoor and outdoor heat, equipment heat dissipation, and heat dissipation from people in summer, which needs to be discharged by the air conditioning system, is the core basis for selecting refrigeration equipment.
6. Moisture load : The total moisture generated by indoor personnel, equipment, water bodies, etc., and the water vapor load that the air conditioning system needs to handle, which directly determines the configuration of dehumidification equipment.
II. Nouns related to core equipment components
1. Chiller : The core unit of HVAC refrigeration, which produces low-temperature chilled water through compression and absorption refrigeration principles to provide a cold source for terminal air conditioning equipment. Common types include screw chillers, centrifugal chillers, and scroll chillers.
2. Cooling Tower : A heat dissipation device配套 with a chiller unit. It removes the waste heat generated by the unit's cooling through heat exchange between water and air, and cools the circulating cooling water.
3. Boiler : The core equipment for heating and heat generation. It produces hot water or steam through combustion, electric heating, etc., to provide a heat source for heating and air conditioning circuits.
4. Combined Air Handling Unit (AHU) : A centralized air handling unit that integrates functions such as fresh air mixing, filtration, heating, cooling, humidification, and air supply. It is often used in centralized air conditioning systems for large commercial buildings and factories.
5. Fan Coil Unit (FCU) : A small air conditioning terminal unit that uses a fan to drive airflow through a cooling and heating coil for heat exchange, thereby regulating indoor temperature and humidity. It is widely used in independent spaces such as office buildings and hotel rooms.
6. Fresh Air Unit (FAU) : A device specifically designed to process outdoor fresh air. It can filter and pre-treat the temperature and humidity of the fresh air, delivering qualified fresh air into the room to ensure the oxygen content and cleanliness of the indoor air.
7. Axial flow fans and centrifugal fans : system ventilation power equipment. Axial flow fans are suitable for ventilation scenarios with large air flow and low air pressure; centrifugal fans have high air pressure and are suitable for air conditioning supply and duct exhaust scenarios.
8. Plate heat exchanger : A device that exchanges heat between hot and cold media through metal plates. It is used in scenarios such as heat exchange in water systems, zoned heating, and waste heat recovery. It has high heat exchange efficiency and small size.
9. Expansion tank : A water system pressure stabilizing device that absorbs the water volume expansion caused by changes in water temperature, maintains stable pressure in air conditioning and heating water systems, and prevents system overpressure or water shortage.
10. Manifold : A water system distribution and collection device that distributes the hot and cold water supplied by the main unit to each terminal branch, while collecting the return water from each branch to achieve zoned water system control.
III. System Operating Parameter Terminology
1. Supply air temperature/Return air temperature : The temperature of the air supplied by the air conditioning equipment to the room is the supply air temperature; the temperature of the air returning to the air conditioning equipment from the room is the return air temperature. These are the core monitoring parameters for system temperature control.
2. Relative humidity (RH) : The percentage of actual water vapor pressure in the air to saturated water vapor pressure at the same temperature. It is the core indicator for air conditioning humidity control. Comfort air conditioning is usually controlled at 40%~60%.
3. Fresh air volume : The amount of fresh outdoor air introduced into the room per unit time. It is determined based on the number of people in the room and the function of the space, and is a key parameter for ensuring indoor air quality.
4. Air exchange rate : The number of times indoor air is replaced by fresh air per unit time. It is a core parameter in ventilation system design, and different standards apply to different functional spaces (offices, computer rooms, clean rooms).
5. Water flow/air volume : These refer to the circulating flow rate of the air conditioning water system and the air delivery flow rate of the air system, respectively, which directly affect the system's heat exchange efficiency and temperature control effect.
6. Static pressure/dynamic pressure/total pressure : Core pressure parameters of the air system. Static pressure maintains the stability of air supply in the pipeline, dynamic pressure is the pressure generated by air flow, and total pressure is the sum of static pressure and dynamic pressure. It is used for fan selection and duct commissioning.
7. COP (Coefficient of Performance) : An energy efficiency index for refrigeration/heating equipment, which refers to the ratio of the effective cooling/heating capacity of the equipment to the input electrical power. The higher the COP value, the higher the energy efficiency and the lower the energy consumption of the equipment.
8. EER (Energy Efficiency Ratio) : An energy efficiency parameter specific to air conditioning and refrigeration, used to evaluate the energy utilization efficiency of equipment under refrigeration conditions, and is the basis for determining the energy-saving level of equipment.
IV. System Technology and Model Terminology
1. Single-pass return air system : The most commonly used form of centralized air conditioning system, which mixes indoor return air with outdoor fresh air and processes them in a unified manner. It has good energy efficiency and is suitable for most public buildings.
2. Secondary return air system : The return air is divided into two parts and mixed with the fresh air. The supply air temperature can be adjusted without secondary heating. It is mostly used in high-precision constant temperature air conditioning scenarios.
3. All-air system : Using air as the sole heat exchange medium, the air is processed by a centralized air conditioning unit and then delivered indoors. It is suitable for large spaces and places with high cooling loads, such as shopping malls and exhibition halls.
4. Air-water system : This type of air conditioning combines air and water systems. Fan coil units process indoor circulating air, while fresh air units supplement fresh air, balancing comfort and energy efficiency. It is the most widely used system.
5. Variable Air Volume (VAV) System : An air conditioning system that can automatically adjust the supply air volume according to changes in indoor load. When the load is low, the air volume is reduced, which greatly reduces the operating energy consumption. It is suitable for office buildings with large load fluctuations.
6. Constant Air Volume (CAV) System : The supply air volume is fixed, and the supply air temperature is adjusted to adapt to the indoor load. The system has a simple structure and stable operation, and is mostly used in process constant temperature spaces.
7. Two-pipe/four-pipe water system : The two-pipe water system uses a single set of pipes for both hot and cold water, which is simple in structure and low in cost; the four-pipe system has independent cooling and heating pipes, which can realize simultaneous cooling and heating in different areas and is suitable for high-end buildings.
8. Dehumidification/Humidification : The core air handling technology of air conditioning. Dehumidification reduces the moisture content of indoor air, while humidification increases the humidity of the air to meet the humidity requirements of comfortable air conditioning and process environments.
V. Specialized Terms in Purification and Ventilation
1. PM2.5/PM10 filtration : The air conditioning fresh air system filters fine particulate matter and inhalable particulate matter in the air, which is the core function of indoor air quality purification.
2. Pre-filter/Medium-efficiency/High-efficiency filter : A graded filtration system for air systems. Pre-filters remove large dust particles, medium-efficiency filters remove fine dust particles, and high-efficiency filters (HEPA) can filter micron-sized particles. They are used in cleanrooms and hospital operating rooms.
3. Positive/Negative Pressure Ventilation : Positive pressure ventilation makes the indoor air pressure higher than the outdoor air pressure, preventing dirty outdoor air from seeping in; negative pressure ventilation makes the indoor air pressure lower than the outdoor air pressure, quickly expelling harmful indoor gases, and is often used in computer rooms and laboratories.
4. Smoke exhaust and ventilation : Fire-fighting dedicated ventilation system, which can quickly exhaust indoor smoke in the event of a fire, ensuring personnel evacuation and fire-fighting operations.
5. Make-up air system : Works in conjunction with the exhaust and smoke extraction system to replenish fresh air into the room, balance indoor air pressure, and prevent excessive negative pressure from causing poor ventilation.
VI. Terminology related to operation and maintenance and fault protection
1. Antifreeze protection : The core protection function of the water system, which automatically starts water circulation or heating in low temperature environments to prevent pipes and equipment from freezing and cracking.
2. Overload protection : Electrical protection for power equipment such as fans, water pumps, and generator sets. Automatic shutdown when the load exceeds the limit to prevent equipment burnout.
3. Differential Pressure Alarm : An alarm is triggered when the differential pressure between the filter and the air duct exceeds the standard, indicating that the filter screen or air duct is blocked and needs to be cleaned and maintained in time.
4. Variable frequency control : The speed of water pumps and fans is adjusted by a frequency converter, and the flow rate and air volume are adaptively adjusted according to the load to achieve energy-saving operation of the system.
5. System pressure stabilization : The system maintains constant water pressure through equipment such as expansion tanks and pressure regulating valves, ensuring stable system operation.
