Common HVACR Technical Terms and Abbreviations

Have you ever stepped into a conversation about heating, ventilation, air conditioning, and refrigeration (HVACR) and felt hopelessly lost amidst a dizzying array of technical jargon? Fear not, intrepid adventurer! This guide will equip you with the knowledge to navigate the complex world of HVACR terminology, demystifying common terms and abbreviations that leave others scratching their heads.

Unlocking the Knowledge:

Understanding these terms empowers you to communicate effectively with HVACR professionals, make informed decisions regarding your own systems, and appreciate the complex technology that keeps us comfortable in diverse environments. Don’t hesitate to explore further!

Airflow and Pressure:

  • CFM: Cubic Feet per Minute – Measurement of air volume flow.
  • CFM/ton: Airflow required per ton of refrigeration capacity.
  • W.C.: Water Column – Measurement of pressure using the height of a water column.
  • kPa: Kilopascal – Unit of pressure in the metric system.
  • Pa: Pascal – Unit of pressure in the metric system.
  • IP: Inches of Water Column – Unit of pressure used in the US.

Temperature and Humidity:

  • Btu: British thermal unit – Unit of heat energy.
  • Ton: Unit of refrigeration capacity equal to 12,000 Btu/hr.
  • °F: Degrees Fahrenheit – Common temperature unit in the US.
  • °C: Degrees Celsius – Common temperature unit in the metric system.
  • RH: Relative Humidity – Percentage of air saturated with water vapor.

Refrigeration and Equipment:

  • SEER: Seasonal Energy Efficiency Ratio – Ratio of cooling output to energy input.
  • COP: Coefficient of Performance – Ratio of cooling output to energy input for heat pumps.
  • EER: Energy Efficiency Ratio – Ratio of cooling output to energy input at specific conditions.
  • BTU/h: British thermal units per hour – Unit of heat transfer rate.
  • AHU: Air Handling Unit – Equipment that heats, cools, and ventilates air.
  • FCU: Fan Coil Unit – Terminal unit that heats or cools air using coils and a fan.
  • DX: Direct Expansion – Refrigeration system where refrigerant directly cools air or liquid.
  • CHC: Chilled Water Coil – Equipment that cools air using chilled water.
  • HX: Heat Exchanger – Equipment that transfers heat between two fluids.

Electrical and Controls:

  • VAC: Volts Alternating Current – Common voltage type in North America.
  • VDC: Volts Direct Current – Common voltage type for electronic components.
  • Hz: Hertz – Unit of frequency (cycles per second).
  • kW: Kilowatt – Unit of electrical power.
  • BMS: Building Management System – System that controls HVAC, lighting, and other building systems.
  • VFD: Variable Frequency Drive – Equipment that controls the speed of electric motors.


  • HVACR: Heating, Ventilation, Air Conditioning, and Refrigeration.
  • ASHRAE: American Society of Heating, Refrigerating and Air-Conditioning Engineers.
  • NFPA: National Fire Protection Association.
  • EPA: Environmental Protection Agency.

Beyond the Basics:

  • MERV: Minimum Efficiency Reporting Value – Rating system for air filter efficiency.
  • IAQ: Indoor Air Quality – Quality of air within a building.
  • VOCs: Volatile Organic Compounds – Organic chemicals that evaporate at room temperature, potentially affecting indoor air quality.
  • DDC: Direct Digital Control – Control system for HVAC equipment using digital communication protocols.
  • BAS: Building Automation System – Comprehensive system for monitoring and controlling various building systems, including HVAC.
  • HVAC Zoning: Dividing a building into separate zones with independent climate control.
  • DOAS: Dedicated Outdoor Air System – System that brings fresh outdoor air directly into a building, often used with energy-efficient ventilation strategies.
  • ECM: Electronically Commutated Motor – High-efficiency electric motor type commonly used in HVAC equipment.
  • RLA: Rated Load Amperes – Maximum operating current of an electrical device.
  • VAV: Variable Air Volume – System that adjusts air volume to different zones based on demand, improving efficiency and comfort.
  • CO2: Carbon dioxide – A natural refrigerant with zero GWP, gaining popularity but requiring specialized equipment due to its high operating pressures.

Advanced Systems and Components:

  • VRF: Variable Refrigerant Flow – System that uses individual refrigerant control in various zones for high efficiency and flexibility.
  • Chillers: Large refrigeration units that produce chilled water for cooling buildings.
  • Boilers: Equipment that generates heat for hydronic heating systems.
  • Cooling Towers: Equipment that dissipates heat from water used in chiller systems.
  • Air Handlers: Dedicated equipment for processing and distributing air in commercial and industrial buildings.
  • Fan Coil Units: Smaller terminal units with coils and fans for heating or cooling specific spaces within a building.
  • Evaporator Coil: Part of the refrigeration system where refrigerant absorbs heat from air or liquid.
  • Condenser Coil: Part of the refrigeration system where refrigerant rejects heat to the environment.
  • Expansion Valve: Controls the flow of refrigerant in the system.
  • Filter Driers: Remove moisture and contaminants from the refrigerant system.


  • HFCs: Hydrofluorocarbons – Common refrigerants with relatively high Global Warming Potential (GWP).
  • HFOs: Hydrofluoroolefins – Newer refrigerants with lower GWP and often reduced flammability.
  • R-410A: Commonly used HFC refrigerant with high efficiency but significant GWP.
  • R-32: Lower GWP HFC refrigerant gaining popularity due to its environmental benefits.
  • CO2: Natural refrigerant with zero GWP but higher operating pressures and system complexity.

Diagnostics and Troubleshooting:

  • Superheat: Temperature difference between refrigerant vapor and its saturation point.
  • Subcooling: Temperature difference between liquid refrigerant and its saturation point.
  • Micromanometer: Instrument for measuring small pressure differences, crucial for refrigerant system testing.
  • Manometer: Instrument for measuring pressure in HVAC systems.
  • Amprobe: Tool for measuring electrical current and voltage in HVAC equipment.
  • Multimeter: Tool for measuring various electrical parameters like voltage, current, and resistance.
  • Fault Codes: Specific error codes displayed by equipment to identify malfunctions.

Advanced Topics and Specialized Systems:

  • HVAC Design: Process of selecting and sizing HVAC equipment for specific building needs and requirements.
  • Air Balance: Adjusting airflow rates in different zones of a building to achieve optimal comfort and efficiency.
  • Psychrometrics: Study of the relationship between temperature, humidity, and other properties of air.
  • Dehumidification: Process of removing moisture from air to control humidity levels.
  • Humidification: Process of adding moisture to air to maintain desired humidity levels.
  • Ventilation Standards: Codes and regulations defining minimum ventilation requirements for healthy indoor environments.
  • Cleanrooms: Controlled environments with extremely low levels of contaminants, requiring specialized HVAC systems.
  • Heat Pumps: Reversible refrigeration systems that provide both heating and cooling.
  • Geothermal Systems: HVAC systems that utilize the Earth’s constant temperature for heating and cooling.

Deeper into Systems and Components:

  • Variable Speed Drives (VSDs): Control the speed of electric motors in HVAC equipment, improving efficiency and reducing energy consumption.
  • Ductwork: Network of tubes that transport conditioned air throughout a building.
  • Plenums: Air chambers used to distribute and mix air before sending it through ductwork.
  • Diffusers and Registers: Outlets installed in ducts to control the direction and volume of airflow.
  • Dampers: Valves that regulate airflow in ducts.
  • Grilles: Decorative covers for diffusers and registers.
  • Filters: Capture dust, pollen, and other airborne particles from airflow.
  • Humidifiers: Add moisture to dry air, often using ultrasonic, evaporative, or steam generation methods.
  • Dehumidifiers: Remove moisture from humid air, using desiccant or refrigeration technologies.
  • Air Purifiers: Filter out specific contaminants like allergens, odors, and volatile organic compounds (VOCs).

Regulations and Standards:

  • ASHRAE Standards: Guidelines for various aspects of HVAC design, installation, and performance.
  • International Building Code (IBC): Sets minimum requirements for building construction, including HVAC systems.
  • National Electrical Code (NEC): Specifies safety standards for electrical installations, including those in HVAC equipment.
  • Energy Star: Government-backed program that identifies energy-efficient HVAC equipment.
  • LEED: Leadership in Energy and Environmental Design – Green building certification program that recognizes buildings with sustainable HVAC systems.

Maintenance and Troubleshooting:

  • Preventive Maintenance: Regular inspections and servicing of HVAC equipment to prevent problems and extend its lifespan.
  • Diagnostics: Identifying the cause of malfunctions in HVAC systems.
  • Repair and Replacement: Fixing or replacing equipment components when necessary.
  • Building Controls Systems (BCS): Centrally monitor and control various building systems, including HVAC, for efficient operation and energy savings.

Additional Resources:

  • HVACR Trade Associations: Organizations like AHRI (Air-Conditioning, Heating, and Refrigeration Institute) offer technical resources, training, and industry news.
  • Technical Publications: Magazines like Heating, Air Conditioning & Refrigeration (HACR) and Engineering News-Record (ENR) provide in-depth information on HVACR technologies and trends.
  • Online Forums and Communities: Platforms like HVAC-Talk and Engineer’s Edge offer opportunities to connect with other professionals and discuss technical topics.

This list provides a starting point for common HVACR technical terms and abbreviations. Remember, various terminology and acronyms exist within specific areas of the field.

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