This glossary highlights technical, regulatory, performance, safety, and commercial acronyms used across the Manufacturing & Industrial Equipment sector, with a focused lens on the HVACR Equipment (HVAC, Refrigeration) Practice. It helps executives, engineers, operators, suppliers, and advisors interpret equipment specifications, standards, and market requirements.
A B C D E F G H I J K L M N O P R S T U V W
| A | |
| A1 | Lower-Toxicity, No-Flame-Propagation Refrigerant Safety Classification: A designation for refrigerants with lower toxicity and no flame propagation under prescribed test conditions, including many legacy fluorocarbon refrigerants. |
| A2L | Lower-Toxicity, Lower-Flammability Refrigerant Safety Classification: A designation for refrigerants with lower toxicity, limited flammability, and low burning velocity. It is central to equipment redesign, charge limits, detection requirements, and refrigerant-transition planning. |
| A3 | Lower-Toxicity, Higher-Flammability Refrigerant Safety Classification: A designation covering highly flammable refrigerants such as propane and isobutane, which require strict charge, ignition-source, ventilation, and service controls. |
| AB | Alkylbenzene: A synthetic refrigeration lubricant commonly associated with hydrochlorofluorocarbon systems and some retrofit applications because of its refrigerant miscibility characteristics. |
| ACCA | Air Conditioning Contractors of America: A U.S. industry association that publishes widely used residential load-calculation, duct-design, equipment-selection, and quality-installation standards. |
| ACFM | Actual Cubic Feet per Minute: Airflow volume measured at the actual temperature, pressure, humidity, and density conditions present in a system rather than at standardized reference conditions. |
| ACH | Air Changes per Hour: The number of times a space’s air volume is replaced in one hour, used to assess ventilation, filtration, pressurization, and contaminant-removal performance. |
| ACR | Air Conditioning and Refrigeration: A designation frequently applied to refrigeration-grade copper tubing, tools, and components manufactured to cleanliness, pressure, and dimensional requirements suitable for refrigerant service. |
| ADP | Apparatus Dew Point: The effective coil-surface temperature at which an air-cooling and dehumidification process would reach saturation, used in coil selection and psychrometric analysis. |
| ADPI | Air Diffusion Performance Index: A measure of how effectively an air-distribution system maintains acceptable air velocity and temperature conditions within the occupied zone. |
| AFDD | Automated Fault Detection and Diagnostics: Software-based monitoring that identifies equipment faults, isolates likely causes, and supports corrective action using operational data from HVAC systems. |
| AFUE | Annual Fuel Utilization Efficiency: A seasonal measure of the percentage of fuel energy converted into useful heat by furnaces and boilers, excluding certain distribution and electrical losses. |
| AHAM | Association of Home Appliance Manufacturers: A trade association that develops performance standards and verification programs for household appliances, including room air cleaners, room air conditioners, and dehumidifiers. |
| AHRI | Air-Conditioning, Heating, and Refrigeration Institute: A trade association that develops equipment-rating standards and administers certification programs used to verify published HVACR performance data. |
| AHRI 1230 | Air-Conditioning, Heating, and Refrigeration Institute Standard 1230 — Performance Rating of Variable Refrigerant Flow Multi-Split Air-Conditioning and Heat Pump Equipment: Establishes rating requirements for multi-split variable-refrigerant-flow systems, supporting comparable capacity and efficiency claims. |
| AHRI 210/240 | Air-Conditioning, Heating, and Refrigeration Institute Standard 210/240 — Performance Rating of Unitary Air-Conditioning and Air-Source Heat Pump Equipment: Defines test and rating requirements for residential and light-commercial unitary cooling and heat-pump equipment. |
| AHRI 340/360 | Air-Conditioning, Heating, and Refrigeration Institute Standard 340/360 — Performance Rating of Commercial and Industrial Unitary Air-Conditioning and Heat Pump Equipment: Provides a common basis for rating the capacity and efficiency of larger unitary systems. |
| AHRI 550/590 | Air-Conditioning, Heating, and Refrigeration Institute Standard 550/590 — Performance Rating of Water-Chilling and Heat Pump Water-Heating Packages Using the Vapor Compression Cycle: Defines full-load and part-load rating methods for vapor-compression chillers and related packages. |
| AHRI 700 | Air-Conditioning, Heating, and Refrigeration Institute Standard 700 — Specifications for Refrigerants: Sets purity requirements for new, reclaimed, and repackaged refrigerants to protect equipment performance, reliability, and serviceability. |
| AHRI 740 | Air-Conditioning, Heating, and Refrigeration Institute Standard 740 — Performance Rating of Refrigerant Recovery Equipment and Recovery/Recycling Equipment: Establishes test methods and performance ratings for equipment used to remove and process refrigerant during service or decommissioning. |
| AHRI 920 | Air-Conditioning, Heating, and Refrigeration Institute Standard 920 — Performance Rating of Direct Expansion-Dedicated Outdoor Air System Units: Defines rating conditions and metrics for equipment that conditions high proportions of outdoor ventilation air. |
| AHU | Air-Handling Unit: A packaged assembly containing components such as fans, filters, coils, dampers, and heat-recovery devices to condition and distribute air. |
| AIM Act | American Innovation and Manufacturing Act: U.S. legislation authorizing the phasedown of hydrofluorocarbon production and consumption, refrigerant-management measures, and sector-based technology transitions. |
| AMCA | Air Movement and Control Association International: An industry organization that develops standards and certification programs for fans, louvers, dampers, air curtains, and other air-system components. |
| AMCA CRP | Air Movement and Control Association International Certified Ratings Program: A third-party program that verifies manufacturers’ published performance ratings for eligible air-movement and control products. |
| ANSI | American National Standards Institute: The U.S. body that coordinates voluntary consensus standards and accredits standards-development processes used by many HVACR codes and product standards. |
| APF | Annual Performance Factor: A seasonal efficiency metric used in several Asian markets to compare the annual cooling and heating output of air conditioners and heat pumps with their annual energy consumption. |
| AREA | Air Conditioning and Refrigeration European Association: A European association representing refrigeration, air-conditioning, and heat-pump contractors, with a focus on refrigerant handling, qualifications, safety, and regulation. |
| ARI | Air-Conditioning and Refrigeration Institute: The former name associated with many legacy equipment-rating standards and certification references that are now maintained under the industry’s current institute. |
| ASHP | Air-Source Heat Pump: Equipment that transfers heat between indoor space or water and outdoor air, providing heating and often reversible cooling. |
| ASHRAE | American Society of Heating, Refrigerating and Air-Conditioning Engineers: A global professional society that publishes influential standards, handbooks, research, and technical guidance for HVACR equipment and systems. |
| ASHRAE 15 | American Society of Heating, Refrigerating and Air-Conditioning Engineers Standard 15 — Safety Standard for Refrigeration Systems: Establishes safeguards for the design, construction, installation, and operation of refrigeration systems. |
| ASHRAE 34 | American Society of Heating, Refrigerating and Air-Conditioning Engineers Standard 34 — Designation and Safety Classification of Refrigerants: Assigns refrigerant numbers and classifies refrigerants by toxicity and flammability characteristics. |
| ASHRAE 55 | American Society of Heating, Refrigerating and Air-Conditioning Engineers Standard 55 — Thermal Environmental Conditions for Human Occupancy: Defines combinations of temperature, humidity, air speed, clothing, and activity that support acceptable human thermal comfort. |
| ASHRAE 62.1 | American Society of Heating, Refrigerating and Air-Conditioning Engineers Standard 62.1 — Ventilation and Acceptable Indoor Air Quality: Sets minimum ventilation and related requirements for most nonresidential buildings. |
| ASHRAE 90.1 | American Society of Heating, Refrigerating and Air-Conditioning Engineers Standard 90.1 — Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings: Establishes minimum energy-efficiency requirements affecting HVAC equipment, controls, ventilation, and system design. |
| ATEL | Acute Toxicity Exposure Limit: A refrigerant concentration intended to limit harmful effects from short-duration accidental exposure and used in safety calculations for occupied spaces. |
| ATWHP | Air-to-Water Heat Pump: A heat pump that extracts energy from outdoor air and delivers it to a water loop for space heating, cooling, or domestic hot-water production. |
| B | |
| B2L | Higher-Toxicity, Lower-Flammability Refrigerant Safety Classification: A designation covering refrigerants with higher toxicity and limited flammability, notably ammonia, requiring rigorous machinery-room, detection, ventilation, and emergency provisions. |
| BACnet | Building Automation and Control Network: An open communication protocol that enables HVAC equipment, controllers, sensors, and building-management systems from different suppliers to exchange operational data. |
| BAS | Building Automation System: A network of controllers, sensors, interfaces, and software used to monitor and coordinate HVAC equipment and other building services. |
| BF | Bypass Factor: The fraction of air passing through a cooling coil that behaves as though it did not contact the effective coil surface, influencing leaving-air temperature and dehumidification. |
| BHP | Brake Horsepower: The mechanical power delivered at a fan, pump, or compressor shaft, used in equipment selection and motor sizing. |
| BLDC | Brushless Direct Current: An electronically commutated motor technology used in variable-speed fans and compressors for efficient, controllable operation. |
| BMS | Building Management System: A supervisory platform that integrates HVAC monitoring, scheduling, alarms, analytics, and control with other building systems. |
| BPHE | Brazed-Plate Heat Exchanger: A compact heat exchanger formed from brazed corrugated plates, widely used in chillers, heat pumps, economizers, and hydronic modules. |
| BTU | British Thermal Unit: A unit of heat equal to the energy required to raise one pound of water by approximately one degree Fahrenheit. |
| BTU/h | British Thermal Units per Hour: A rate of heat transfer commonly used to state heating and cooling capacity in North American equipment specifications. |
| C | |
| CAA | Clean Air Act: The principal U.S. air-pollution law underpinning refrigerant management, technician certification, venting prohibitions, and several emissions requirements affecting HVACR products. |
| CAC | Central Air Conditioner: A system that provides cooling from a central refrigeration unit and distributes conditioned air through ducts or another building-wide distribution network. |
| CADR | Clean Air Delivery Rate: A performance measure expressing the volume of particle-free air an air cleaner delivers, combining airflow with contaminant-removal efficiency. |
| CARB | California Air Resources Board: A state regulator whose refrigerant, emissions, and equipment rules often influence product design and market requirements beyond California. |
| CARO | Certified Assistant Refrigeration Operator: A credential covering foundational knowledge for personnel operating and maintaining industrial refrigeration systems, particularly ammonia installations. |
| CAV | Constant Air Volume: An air-distribution arrangement that maintains relatively constant airflow while varying supply-air temperature or equipment cycling to meet load. |
| CCHP | Cold-Climate Heat Pump: An air-source heat pump designed to maintain useful heating capacity and efficiency at substantially lower outdoor temperatures than conventional products. |
| CEER | Combined Energy Efficiency Ratio: A cooling-efficiency metric that incorporates active-mode energy use together with standby and off-mode consumption for applicable equipment categories. |
| CFC | Chlorofluorocarbon: A class of high-ozone-depletion refrigerants largely phased out under international and national controls but still relevant to legacy equipment and recovery obligations. |
| CFM | Cubic Feet per Minute: A volumetric airflow rate used to size fans, ducts, filters, coils, diffusers, and ventilation equipment. |
| CHW | Chilled Water: Water cooled by a chiller or heat pump and circulated to air handlers, fan coils, or process loads as a heat-transfer medium. |
| CHWR | Chilled-Water Return: The warmer water returning from cooling loads to a chiller, used with supply temperature to evaluate system temperature difference and capacity. |
| CHWS | Chilled-Water Supply: The cooled water leaving a chiller and entering the distribution system, commonly monitored for equipment control and performance verification. |
| CIRO | Certified Industrial Refrigeration Operator: An advanced credential for personnel responsible for operating, troubleshooting, and maintaining industrial refrigeration systems. |
| COP | Coefficient of Performance: The ratio of useful heating or cooling output to energy input at stated conditions, providing a dimensionless measure of equipment efficiency. |
| CPR | Crankcase Pressure Regulator: A suction-line control valve that limits compressor inlet pressure and motor loading during startup or high-load conditions. |
| CRAC | Computer Room Air Conditioner: Precision cooling equipment with an integral refrigeration circuit designed to control temperature, humidity, and airflow in data and telecommunications spaces. |
| CRAH | Computer Room Air Handler: Precision air-handling equipment that typically uses chilled water rather than an integral compressor to remove heat from data-center spaces. |
| CSA | Canadian Standards Association: The standards organization now operating as CSA Group, whose codes, product standards, testing, and certification services apply to HVACR equipment in Canada and other markets. |
| CSA B52 | Canadian Standards Association B52 — Mechanical Refrigeration Code: Establishes Canadian safety requirements for the design, construction, installation, operation, and maintenance of mechanical refrigeration systems. |
| CSPF | Cooling Seasonal Performance Factor: The ratio of seasonal cooling output to seasonal energy consumption under defined climate and load assumptions, used in several international efficiency frameworks. |
| CTI | Cooling Technology Institute: An industry organization that develops standards, thermal-performance certification, and technical guidance for cooling towers and related evaporative heat-rejection equipment. |
| CU | Condensing Unit: A packaged refrigeration assembly typically containing a compressor, condenser, fan or pump, controls, and receiver for connection to a remote evaporator. |
| D | |
| dB(A) | A-Weighted Decibel: A sound-pressure or sound-power level adjusted to approximate human hearing sensitivity, widely used for HVAC equipment noise ratings. |
| DBT | Dry-Bulb Temperature: The ordinary air temperature measured without accounting for evaporative cooling, used with humidity data in psychrometric and load calculations. |
| DCV | Demand-Controlled Ventilation: A control approach that adjusts outdoor-air delivery according to measured occupancy or contaminant indicators, reducing unnecessary conditioning energy. |
| DDC | Direct Digital Control: Microprocessor-based control of HVAC equipment using digital inputs, outputs, logic, schedules, and network communications. |
| DHW | Domestic Hot Water: Heated potable water supplied for washing, sanitation, and similar uses, increasingly produced by high-efficiency heat-pump water heaters and integrated systems. |
| DOAS | Dedicated Outdoor Air System: Equipment designed to condition and deliver required ventilation air separately from systems handling primarily sensible space loads. |
| DOE | United States Department of Energy: The federal department responsible for appliance and equipment energy-conservation standards, test procedures, certification requirements, and enforcement. |
| DPT | Dew-Point Temperature: The temperature at which air becomes saturated and water begins to condense, important for dehumidification, coil design, condensation control, and comfort. |
| DX | Direct Expansion: A refrigeration configuration in which refrigerant evaporates directly within the cooling coil serving the air or process load. |
| E | |
| ECM | Electronically Commutated Motor: A brushless motor with integrated electronic control that enables efficient variable-speed operation in fans, pumps, and other HVAC components. |
| EEV | Electronic Expansion Valve: An electronically actuated refrigerant-metering device that enables precise superheat, capacity, and system-efficiency control over a broad operating range. |
| EER | Energy Efficiency Ratio: The cooling output in British thermal units per hour divided by electrical input in watts at a specified rating condition. |
| EER2 | Energy Efficiency Ratio 2: A U.S. cooling-efficiency metric determined under updated test procedures and external-static-pressure conditions for applicable residential equipment. |
| EMS | Energy Management System: A platform that monitors and optimizes equipment schedules, setpoints, demand, and energy consumption across a facility or portfolio. |
| EN 14511 | European Standard 14511 — Air Conditioners, Liquid Chilling Packages and Heat Pumps for Space Heating and Cooling and Process Chillers: Defines European test methods and performance-rating conditions for covered equipment. |
| EN 14825 | European Standard 14825 — Air Conditioners, Liquid Chilling Packages and Heat Pumps with Electrically Driven Compressors for Space Heating and Cooling: Establishes part-load testing and seasonal-performance calculations used in European product ratings. |
| EN 378 | European Standard 378 — Refrigerating Systems and Heat Pumps: Safety and Environmental Requirements: Defines European requirements for system design, installation, operation, maintenance, and refrigerant-related safety. |
| EPA | United States Environmental Protection Agency: The federal regulator responsible for refrigerant-transition rules, emissions controls, recovery and recycling requirements, and environmental programs affecting HVACR equipment. |
| EPA Section 608 | United States Environmental Protection Agency Clean Air Act Section 608: The regulatory framework governing stationary refrigerant handling, technician certification, sales restrictions, recovery, recycling, reclamation, and venting prohibitions. |
| EPCA | Energy Policy and Conservation Act: The U.S. statute providing core authority for federal energy-conservation standards and test procedures covering many HVAC and water-heating products. |
| EPEE | European Partnership for Energy and the Environment: An industry association representing European refrigeration, air-conditioning, and heat-pump stakeholders on refrigerants, energy efficiency, decarbonization, and regulation. |
| EPR | Evaporator Pressure Regulator: A valve installed in the suction line to maintain a minimum evaporating pressure and corresponding coil temperature under varying load. |
| EPREL | European Product Registry for Energy Labelling: The European Union database in which suppliers register covered energy-related products and submit required efficiency and product information. |
| ErP | Energy-related Products: The European ecodesign framework establishing minimum efficiency, emissions, sound, information, and other requirements for covered heating and cooling products. |
| ERV | Energy Recovery Ventilator: Ventilation equipment that transfers sensible heat and moisture between exhaust and outdoor-air streams to reduce conditioning loads. |
| ESEER | European Seasonal Energy Efficiency Ratio: A weighted part-load cooling-efficiency metric historically used to compare chillers under representative European operating conditions. |
| ESP | External Static Pressure: The resistance outside packaged equipment that its fan must overcome, including pressure losses through connected ducts, filters, grilles, and accessories. |
| ETL | Electrical Testing Laboratories Listed Mark: A product-safety certification mark administered by Intertek indicating that equipment has been evaluated to applicable North American safety standards. |
| EVI | Enhanced Vapor Injection: A compressor-cycle arrangement that injects intermediate-pressure refrigerant vapor to improve heating capacity, efficiency, or discharge-temperature control under demanding conditions. |
| EWT | Entering Water Temperature: The water temperature measured at an equipment inlet, used to define operating conditions and calculate heat-transfer performance. |
| F | |
| F-gas | Fluorinated Greenhouse Gas: A category that includes many refrigerants subject to European and other controls covering supply, use, leakage, servicing, reporting, and phasedown. |
| FAHU | Fresh Air-Handling Unit: An air-handling unit designed primarily to filter, heat, cool, dehumidify, or otherwise condition outdoor ventilation air. |
| FCU | Fan-Coil Unit: A terminal unit containing a fan and one or more heating or cooling coils, typically connected to a central water system. |
| FDD | Fault Detection and Diagnostics: The process of identifying abnormal equipment behavior and determining probable causes using sensors, rules, models, or analytics. |
| FGR | Flue Gas Recirculation: A combustion technique that returns a portion of exhaust gas to the burner to reduce flame temperature and nitrogen-oxide formation. |
| FLA | Full-Load Amperes: The current drawn by a motor at rated load and operating conditions, used for wiring, protection, controls, and component selection. |
| FPI | Fins per Inch: The density of fins on a heat-exchanger coil, affecting heat transfer, air-pressure drop, fouling behavior, and cleanability. |
| FPM | Feet per Minute: A velocity unit used for air movement through ducts, coils, filters, louvers, and occupied zones. |
| FSD | Fire/Smoke Damper: A listed duct device that closes to limit the spread of fire and smoke through air-distribution penetrations and assemblies. |
| G | |
| GHG | Greenhouse Gas: A gas that contributes to atmospheric warming; both refrigerant emissions and energy-related emissions are important when evaluating equipment climate impact. |
| GPM | Gallons per Minute: A volumetric water-flow rate used to size and evaluate chillers, boilers, heat pumps, coils, pumps, and heat exchangers. |
| GSHP | Ground-Source Heat Pump: A heat pump that exchanges heat with the ground or groundwater, taking advantage of relatively stable subsurface temperatures. |
| GWP | Global Warming Potential: A relative measure of the heat-trapping impact of a greenhouse gas compared with carbon dioxide over a specified time horizon. |
| H | |
| HACR | Heating, Air Conditioning, and Refrigeration: A circuit-breaker designation historically associated with the inrush and overload characteristics of motors and grouped loads used in this equipment. |
| HARDI | Heating, Air-conditioning & Refrigeration Distributors International: A trade association representing wholesale distributors and supply-chain partners serving heating, cooling, and refrigeration markets. |
| HC | Hydrocarbon: A class of low-global-warming-potential refrigerants, including propane and isobutane, valued for thermodynamic performance but requiring flammability controls. |
| HCFC | Hydrochlorofluorocarbon: A class of ozone-depleting refrigerants introduced partly as transitional replacements for chlorofluorocarbons and now subject to phaseout controls. |
| HEPA | High-Efficiency Particulate Air: A high-performance filtration classification used where very effective removal of fine airborne particles is required. |
| HFC | Hydrofluorocarbon: A non-ozone-depleting refrigerant class whose members may have significant global-warming potential and are subject to phasedown policies. |
| HFO | Hydrofluoroolefin: A class of unsaturated fluorinated refrigerants with generally low global-warming potential, used alone or in blends for next-generation equipment. |
| HGBP | Hot-Gas Bypass: A capacity-control method that routes discharge gas to the low-pressure side to prevent excessively low evaporating pressure at light load. |
| HGRH | Hot-Gas Reheat: A dehumidification arrangement that uses compressor discharge heat to reheat air after overcooling and moisture removal. |
| HP | Heat Pump: Refrigeration-cycle equipment that transfers heat from a lower-temperature source to a higher-temperature sink and may provide heating, cooling, or both. |
| HPWH | Heat Pump Water Heater: Equipment that transfers heat from surrounding air or another source into stored or circulating water, reducing direct electrical or fuel consumption. |
| HRAI | Heating, Refrigeration and Air Conditioning Institute of Canada: A Canadian industry association representing manufacturers, wholesalers, and contractors and providing technical, regulatory, and training resources. |
| HRV | Heat Recovery Ventilator: Ventilation equipment that transfers sensible heat between outgoing and incoming air streams without intentionally transferring moisture. |
| HSPF | Heating Seasonal Performance Factor: A legacy U.S. seasonal heating-efficiency metric expressing delivered heat relative to electrical energy consumed over a representative season. |
| HSPF2 | Heating Seasonal Performance Factor 2: The updated U.S. seasonal heating-efficiency metric calculated under revised test procedures intended to better represent installed operating conditions. |
| HTF | Heat-Transfer Fluid: Water, brine, glycol solution, oil, or another fluid used to transport thermal energy between equipment and loads. |
| HVAC | Heating, Ventilation, and Air Conditioning: The equipment and systems used to control indoor temperature, humidity, air movement, ventilation, and air quality. |
| HVACR | Heating, Ventilation, Air Conditioning, and Refrigeration: The broader field encompassing comfort conditioning, ventilation, heat pumps, commercial cooling, and refrigeration equipment. |
| HX | Heat Exchanger: A component that transfers heat between fluids, or between a fluid and air, while normally keeping the streams physically separated. |
| I | |
| IAQ | Indoor Air Quality: The condition of indoor air with respect to contaminants, ventilation, humidity, and occupant health and comfort. |
| ICC | International Code Council: The organization that develops model building, mechanical, fuel-gas, and energy codes widely adopted by U.S. jurisdictions. |
| IEC | International Electrotechnical Commission: A global standards body that publishes electrical and product-safety requirements used in the design and certification of HVACR equipment. |
| IEC 60335-2-40 | International Electrotechnical Commission Standard 60335-2-40 — Particular Requirements for Electrical Heat Pumps, Air-Conditioners and Dehumidifiers: A key international product-safety standard addressing electrical, mechanical, thermal, and flammable-refrigerant risks. |
| IECC | International Energy Conservation Code: A model code establishing building energy requirements that influence equipment efficiency, controls, economizers, ventilation, and system design. |
| IEER | Integrated Energy Efficiency Ratio: A weighted part-load cooling-efficiency metric used for commercial unitary air-conditioning and heat-pump equipment. |
| IFGC | International Fuel Gas Code: A model code governing fuel-gas piping, combustion air, venting, and gas-fired appliances, including furnaces, boilers, and rooftop units. |
| IIAR | International Institute of All-Natural Refrigeration: An industry organization that publishes widely adopted standards and guidance for ammonia and other natural-refrigerant systems. |
| IIAR 2 | International Institute of All-Natural Refrigeration Standard 2 — Design of Safe Closed-Circuit Ammonia Refrigeration Systems: Establishes minimum design requirements for ammonia refrigeration equipment and systems. |
| IIAR 6 | International Institute of All-Natural Refrigeration Standard 6 — Inspection, Testing, and Maintenance of Closed-Circuit Ammonia Refrigeration Systems: Defines minimum practices for maintaining the mechanical integrity and safe operation of ammonia systems. |
| IIAR 9 | International Institute of All-Natural Refrigeration Standard 9 — Minimum System Safety Requirements for Existing Closed-Circuit Ammonia Refrigeration Systems: Establishes baseline safety requirements for installations that predate current design standards. |
| IIR | International Institute of Refrigeration: An intergovernmental science and technology organization supporting research, standards, data, and knowledge exchange across refrigeration and heat-pump applications. |
| IMC | International Mechanical Code: A model code covering mechanical systems, ventilation, combustion air, exhaust, refrigeration, ductwork, and equipment installation. |
| IPLV | Integrated Part-Load Value: A weighted efficiency metric representing chiller performance at several part-load conditions using standardized operating assumptions. |
| IRA | Inflation Reduction Act: U.S. legislation providing tax incentives, rebates, manufacturing support, and market stimulus for qualifying heat pumps and other efficient building technologies. |
| ISHRAE | Indian Society of Heating, Refrigerating and Air Conditioning Engineers: A professional society that develops technical guidance, standards, education, and industry programs for India’s cooling, heating, and refrigeration markets. |
| ISO | International Organization for Standardization: A global standards body whose test, safety, quality, and environmental standards support equipment design, certification, and international trade. |
| ISO 5149 | International Organization for Standardization Standard 5149 — Refrigerating Systems and Heat Pumps: Safety and Environmental Requirements: Provides international requirements for system design, construction, installation, operation, maintenance, repair, and refrigerant safety. |
| ISO 817 | International Organization for Standardization Standard 817 — Refrigerants: Designation and Safety Classification: Defines refrigerant naming and classification according to composition, toxicity, and flammability. |
| J | |
| JRAIA | Japan Refrigeration and Air Conditioning Industry Association: The Japanese industry association involved in product standards, statistics, policy, refrigerant transition, and international coordination. |
| K | |
| kW | Kilowatt: A unit of power used to express electrical input and heating or cooling output in equipment specifications and energy calculations. |
| kW/ton | Kilowatts per Ton of Refrigeration: A chiller-efficiency metric expressing electrical input per unit of cooling capacity; lower values indicate less input power at the stated conditions. |
| L | |
| LCCP | Life Cycle Climate Performance: A measure of total climate impact that includes direct refrigerant emissions, energy-related emissions, and selected lifecycle effects such as manufacturing and end-of-life treatment. |
| LDAR | Leak Detection and Repair: A structured program for identifying, documenting, repairing, and verifying refrigerant leaks to reduce emissions, losses, and compliance risk. |
| LFL | Lower Flammability Limit: The minimum concentration of refrigerant vapor in air capable of propagating a flame under specified test conditions. |
| LMTD | Log Mean Temperature Difference: The effective average temperature driving force across a heat exchanger when the temperature difference varies from one end to the other. |
| LRA | Locked-Rotor Amperes: The current a motor draws when energized but not rotating, important for compressor starting, conductor sizing, and protective-device coordination. |
| LSHX | Liquid-Suction Heat Exchanger: A device that transfers heat from the liquid refrigerant line to the suction line, increasing subcooling and superheat while changing cycle performance. |
| LWT | Leaving Water Temperature: The water temperature measured at an equipment outlet, commonly used as a control target and rating condition for chillers and heat pumps. |
| M | |
| MAU | Make-Up Air Unit: Equipment that supplies conditioned outdoor air to replace air removed by exhaust systems and maintain building pressure. |
| MAWP | Maximum Allowable Working Pressure: The highest pressure a vessel or component is permitted to withstand at a specified temperature under its design code. |
| MBH | Thousand British Thermal Units per Hour: A heating or cooling capacity unit in which the letter M represents one thousand, commonly used for boilers, furnaces, coils, and commercial equipment. |
| MCA | Minimum Circuit Ampacity: The minimum current-carrying capacity required for conductors supplying a piece of equipment, as stated on its nameplate. |
| MCHE | Microchannel Heat Exchanger: A compact aluminum heat exchanger using small parallel flow passages to reduce refrigerant charge and improve heat-transfer density. |
| MCS | Microgeneration Certification Scheme: A United Kingdom certification framework covering eligible low-carbon products and installers, including heat pumps used in incentive-supported installations. |
| MEPS | Minimum Energy Performance Standards: Mandatory efficiency thresholds that products must meet to be sold in a jurisdiction, often supported by prescribed tests, registration, and labeling. |
| MERV | Minimum Efficiency Reporting Value: A rating describing an air filter’s particle-removal performance across specified particle-size ranges. |
| MO | Mineral Oil: A petroleum-derived lubricant traditionally used with several legacy refrigerants and compressors, with limited compatibility in many newer refrigerant applications. |
| MOCP | Maximum Overcurrent Protection: The largest permitted fuse or circuit-breaker rating for a piece of equipment, as specified on its nameplate. |
| MOPD | Maximum Operating Pressure Differential: The greatest pressure difference across a valve at which its actuator can reliably open or close the device. |
| N | |
| NATE | North American Technician Excellence: A certification organization that assesses technician knowledge in installation, service, controls, air distribution, heat pumps, and related specialties. |
| NC | Noise Criteria: A set of frequency-based curves used to characterize acceptable background sound levels from building services in occupied spaces. |
| NEEP | Northeast Energy Efficiency Partnerships: A U.S. regional nonprofit whose heat-pump product lists, performance data, and market programs influence cold-climate equipment qualification and adoption. |
| NFPA | National Fire Protection Association: A standards-development organization whose fire, electrical, ventilation, and combustion codes affect equipment design and installation. |
| NFPA 90A | National Fire Protection Association Standard 90A — Installation of Air-Conditioning and Ventilating Systems: Establishes fire and smoke safeguards for air-distribution systems serving buildings other than certain smaller residential occupancies. |
| NFPA 90B | National Fire Protection Association Standard 90B — Installation of Warm Air Heating and Air-Conditioning Systems: Establishes fire-safety requirements for residential and smaller warm-air heating and cooling systems. |
| NOx | Nitrogen Oxides: Combustion pollutants regulated in many markets, driving burner, furnace, boiler, water-heater, and emissions-control design decisions. |
| NPLV | Non-Standard Part-Load Value: A chiller part-load efficiency calculation based on project-specific operating conditions rather than the standardized assumptions used for published integrated ratings. |
| NRCan | Natural Resources Canada: The federal department that administers Canadian energy-efficiency regulations, product reporting, labeling, testing, and market-transformation programs. |
| NRTL | Nationally Recognized Testing Laboratory: A laboratory recognized by the U.S. Occupational Safety and Health Administration to test and certify products to applicable safety standards. |
| O | |
| OAT | Outdoor Air Temperature: The ambient temperature used in load calculations, capacity ratings, economizer control, defrost logic, and heat-pump operating limits. |
| ODL | Oxygen Deprivation Limit: A refrigerant concentration limit intended to prevent unsafe oxygen displacement following a release into an occupied space. |
| ODP | Ozone Depletion Potential: A relative measure of a substance’s ability to damage stratospheric ozone compared with a reference compound. |
| OSHA | Occupational Safety and Health Administration: The U.S. workplace-safety regulator whose requirements affect refrigerant exposure, electrical safety, hazardous chemicals, and process safety in industrial refrigeration. |
| P | |
| PAG | Polyalkylene Glycol: A synthetic lubricant used in selected refrigeration and air-conditioning compressors, with application depending on refrigerant compatibility and moisture-control requirements. |
| PED | Pressure Equipment Directive: European Union legislation governing the design, conformity assessment, manufacture, and marking of pressure equipment and assemblies above specified limits. |
| PHA | Process Hazard Analysis: A structured assessment used to identify and control hazards in covered industrial refrigeration processes, especially large ammonia systems. |
| PHE | Plate Heat Exchanger: A heat exchanger using a stack of plates to provide high surface area and compact thermal transfer between fluid circuits. |
| PM2.5 | Particulate Matter 2.5 Micrometers or Smaller: Fine airborne particles that can penetrate deeply into the lungs and are an important target for indoor-air filtration and ventilation strategies. |
| PMV | Predicted Mean Vote: A thermal-comfort index predicting the average sensation of a large group on a scale from cold to hot under specified environmental and personal conditions. |
| POE | Polyolester: A synthetic refrigeration lubricant widely used with hydrofluorocarbon and hydrofluoroolefin refrigerants, requiring careful moisture control because it is hygroscopic. |
| PPD | Predicted Percentage of Dissatisfied: A thermal-comfort index estimating the share of occupants likely to find environmental conditions unacceptable. |
| PSC | Permanent Split Capacitor: A single-phase induction-motor design traditionally used in fans and blowers, generally offering less speed control and lower efficiency than modern electronically commutated alternatives. |
| PSIA | Pounds per Square Inch Absolute: Pressure measured relative to a perfect vacuum, used in thermodynamic calculations and refrigerant property data. |
| PSIG | Pounds per Square Inch Gauge: Pressure measured relative to local atmospheric pressure, commonly displayed on service gauges and equipment instruments. |
| PSM | Process Safety Management: A U.S. regulatory framework requiring systematic control of hazards in covered processes, including qualifying ammonia refrigeration installations. |
| PSSR | Pre-Startup Safety Review: A formal verification that equipment, procedures, training, and safeguards are ready before a new or materially modified covered process begins operation. |
| PTAC | Packaged Terminal Air Conditioner: A self-contained through-the-wall room unit commonly used in hotels, apartments, healthcare facilities, and similar buildings. |
| PTHP | Packaged Terminal Heat Pump: A through-the-wall packaged unit that provides reversible heat-pump heating and cooling, usually with supplemental resistance heat. |
| PVE | Polyvinyl Ether: A synthetic refrigeration lubricant used with selected modern refrigerants and compressors because of its miscibility, lubricity, and moisture-related characteristics. |
| R | |
| R-1234ze(E) | Refrigerant 1234ze(E) — trans-1,3,3,3-Tetrafluoropropene: A low-global-warming-potential hydrofluoroolefin used in chillers, heat pumps, and as a component of refrigerant blends. |
| R-134a | Refrigerant 134a — 1,1,1,2-Tetrafluoroethane: A hydrofluorocarbon historically used in chillers and medium-temperature refrigeration that is being replaced in many applications because of its climate impact. |
| R-22 | Refrigerant 22 — Chlorodifluoromethane: A hydrochlorofluorocarbon widely used in legacy air-conditioning and refrigeration equipment and now subject to phaseout and strict servicing constraints. |
| R-290 | Refrigerant 290 — Propane: A highly flammable hydrocarbon refrigerant with very low global-warming potential and strong thermodynamic performance in charge-limited equipment. |
| R-32 | Refrigerant 32 — Difluoromethane: A lower-global-warming-potential hydrofluorocarbon classified as lower flammability and used in many new air conditioners and heat pumps. |
| R-404A | Refrigerant 404A — Hydrofluorocarbon Blend: A high-global-warming-potential blend historically prevalent in commercial refrigeration and now a major focus of retrofit and replacement programs. |
| R-407C | Refrigerant 407C — Zeotropic Hydrofluorocarbon Blend: A non-ozone-depleting blend used in air-conditioning and heat-pump applications, with temperature glide that must be considered in design and service. |
| R-410A | Refrigerant 410A — Near-Azeotropic Hydrofluorocarbon Blend: A high-pressure refrigerant widely used in unitary air conditioners and heat pumps and being superseded by lower-climate-impact alternatives. |
| R-448A | Refrigerant 448A — Hydrofluoroolefin/Hydrofluorocarbon Blend: A lower-global-warming-potential, nonflammable blend used as an alternative in commercial refrigeration, with notable temperature glide. |
| R-449A | Refrigerant 449A — Hydrofluoroolefin/Hydrofluorocarbon Blend: A nonflammable, lower-global-warming-potential blend used in new and retrofit commercial refrigeration applications. |
| R-454B | Refrigerant 454B — Hydrofluoroolefin/Hydrofluorocarbon Blend: A lower-flammability blend adopted as a lower-global-warming-potential replacement for common unitary air-conditioning and heat-pump refrigerants. |
| R-513A | Refrigerant 513A — Hydrofluoroolefin/Hydrofluorocarbon Blend: A nonflammable, lower-global-warming-potential alternative used in chillers and medium-temperature refrigeration equipment. |
| R-600a | Refrigerant 600a — Isobutane: A highly flammable hydrocarbon refrigerant with very low global-warming potential, widely used in small factory-sealed refrigeration appliances. |
| R-717 | Refrigerant 717 — Ammonia: A highly efficient natural refrigerant with negligible global-warming impact, widely used in industrial refrigeration but requiring toxicity and flammability safeguards. |
| R-744 | Refrigerant 744 — Carbon Dioxide: A nonflammable natural refrigerant with very low global-warming potential that operates at high pressures and is used in transcritical and subcritical systems. |
| RAC | Room Air Conditioner: A self-contained unit designed to cool an individual room, commonly installed through a window or wall opening. |
| RAT | Return Air Temperature: The temperature of air returning from a conditioned space to equipment, used to assess load, control operation, and calculate capacity. |
| RCL | Refrigerant Concentration Limit: A safety-based concentration used to determine allowable refrigerant quantities in occupied spaces and inform mitigation requirements. |
| RDS | Refrigerant Detection System: Sensors, controls, alarms, and mitigation functions used to identify refrigerant leaks and initiate ventilation, shutdown, or other protective actions. |
| RETA | Refrigerating Engineers & Technicians Association: A professional organization providing education and certification for operators and technicians working with industrial refrigeration systems. |
| RH | Relative Humidity: The ratio of actual water-vapor pressure to saturation vapor pressure at the same temperature, expressed as a percentage. |
| RLA | Rated-Load Amperes: A nameplate current value used for compressor and equipment application, conductor selection, and protective-device coordination under rated conditions. |
| RMP | Refrigerant Management Plan: A documented framework for inventory control, leak prevention, recovery, reclamation, recordkeeping, and responsible refrigerant disposition. |
| RMP | Risk Management Program: A U.S. environmental regulatory program requiring covered facilities, including qualifying ammonia refrigeration plants, to prevent and prepare for accidental chemical releases. |
| RPM | Revolutions per Minute: A rotational-speed unit used for compressors, fans, pumps, and motors and directly related to airflow, capacity, sound, and power consumption. |
| RTU | Rooftop Unit: Packaged heating, cooling, ventilation, and air-distribution equipment designed for installation on a building roof. |
| S | |
| SACC | Seasonally Adjusted Cooling Capacity: A U.S. metric for portable air conditioners that adjusts measured cooling capacity for cycling, infiltration, and other effects intended to reflect seasonal use. |
| SAT | Supply Air Temperature: The temperature of air delivered from equipment into the distribution system or conditioned space, used for control and performance analysis. |
| SC | Subcooling: The amount by which liquid refrigerant temperature is below its saturation temperature at the measured pressure, used to assess charge and liquid-line condition. |
| SCFM | Standard Cubic Feet per Minute: Gas or airflow volume corrected to specified standard temperature and pressure conditions, enabling consistent equipment comparisons. |
| SCOP | Seasonal Coefficient of Performance: The ratio of seasonal heating output to seasonal energy consumption under a prescribed climate and load profile. |
| SDT | Saturated Discharge Temperature: The saturation temperature corresponding to high-side refrigerant pressure, used in condenser and compressor performance analysis. |
| SEER | Seasonal Energy Efficiency Ratio: A legacy U.S. metric comparing seasonal cooling output with seasonal electrical consumption for residential and light-commercial equipment. |
| SEER2 | Seasonal Energy Efficiency Ratio 2: The updated U.S. seasonal cooling-efficiency metric calculated under revised test procedures and external-static-pressure conditions. |
| SFP | Specific Fan Power: The electrical power required to move a unit volume of air through a fan system, used to evaluate air-distribution efficiency. |
| SH | Superheat: The amount by which refrigerant vapor temperature exceeds saturation temperature at the measured pressure, indicating the absence of liquid at that point. |
| SHF | Sensible Heat Factor: The proportion of total heat transfer associated with temperature change rather than moisture removal, commonly used in psychrometric process analysis. |
| SHR | Sensible Heat Ratio: The ratio of sensible cooling capacity to total cooling capacity, indicating an equipment configuration’s balance between temperature reduction and dehumidification. |
| SMACNA | Sheet Metal and Air Conditioning Contractors’ National Association: An industry association whose standards address duct construction, leakage, testing, air-system installation, and sheet-metal practices. |
| SNAP | Significant New Alternatives Policy: A U.S. environmental program that evaluates and lists acceptable or unacceptable substitutes for ozone-depleting substances by end use. |
| SPF | Seasonal Performance Factor: The ratio of useful thermal energy delivered over a season to total energy consumed, often used to assess installed heat-pump system performance. |
| SPL | Sound Pressure Level: The acoustic pressure measured at a specified location and distance, influenced by the sound source, room, barriers, and measurement conditions. |
| SST | Saturated Suction Temperature: The saturation temperature corresponding to low-side refrigerant pressure, used to evaluate evaporator and compressor operating conditions. |
| SWL | Sound Power Level: The total acoustic energy emitted by equipment independent of room and distance effects, allowing products to be compared on a consistent basis. |
| T | |
| TAB | Testing, Adjusting, and Balancing: The field process of measuring and setting air and water flows so installed systems meet design and operational requirements. |
| TD | Temperature Difference: The difference between two relevant temperatures, such as room air and evaporating refrigerant, used in coil sizing and capacity analysis. |
| TEWI | Total Equivalent Warming Impact: A climate-impact measure combining direct refrigerant emissions with indirect emissions from energy consumption over equipment life. |
| TR | Ton of Refrigeration: A cooling-capacity unit equal to 12,000 British thermal units per hour, commonly used for chillers and larger cooling systems. |
| TSP | Total Static Pressure: The difference between fan inlet and discharge static pressure, used to select fans and evaluate air-system resistance. |
| TXV | Thermostatic Expansion Valve: A mechanical refrigerant-metering device that modulates flow to maintain target superheat at the evaporator outlet. |
| U | |
| UEF | Uniform Energy Factor: A U.S. water-heater efficiency metric based on useful hot-water energy delivered relative to total energy consumed under a prescribed test procedure. |
| UFL | Upper Flammability Limit: The maximum vapor concentration in air at which a flame can propagate under specified test conditions. |
| UL | Underwriters Laboratories: The historical expanded name associated with UL Solutions, which develops product-safety standards and provides testing and certification used throughout HVACR markets. |
| UL 60335-2-40 | Underwriters Laboratories Standard 60335-2-40 — Particular Requirements for Electrical Heat Pumps, Air-Conditioners and Dehumidifiers: A key North American product-safety standard covering electrical, mechanical, thermal, and flammable-refrigerant safeguards. |
| ULN | Ultra-Low Nitrogen Oxides: A designation for combustion equipment engineered to meet especially stringent nitrogen-oxide emissions limits. |
| UMC | Uniform Mechanical Code: A model code governing HVAC, combustion, ventilation, refrigeration, duct, and mechanical-system installations in adopting jurisdictions. |
| UVC | Ultraviolet-C: Short-wavelength ultraviolet radiation used in some air-handling systems for coil irradiation and microbial-control applications. |
| UVGI | Ultraviolet Germicidal Irradiation: The use of germicidal ultraviolet energy to inactivate susceptible microorganisms on surfaces or in moving air. |
| V | |
| VAV | Variable Air Volume: An air-distribution approach that changes airflow to individual zones or systems in response to load while generally maintaining a controlled supply-air temperature. |
| VFD | Variable-Frequency Drive: An electronic device that varies motor speed by changing supplied frequency and voltage, reducing part-load energy use in fans, pumps, and compressors. |
| VOC | Volatile Organic Compound: An airborne carbon-containing chemical that readily evaporates and may affect indoor air quality, ventilation needs, and filtration strategies. |
| VRF | Variable Refrigerant Flow: A multi-split system that modulates refrigerant flow to multiple indoor units, allowing zoned heating and cooling with variable-capacity outdoor equipment. |
| VRV | Variable Refrigerant Volume: A trademarked term used for a manufacturer’s variable-refrigerant-flow technology and often encountered in specifications for multi-zone systems. |
| VSD | Variable-Speed Drive: A general category of drive technology that modulates motor or compressor speed to match capacity with load and improve part-load performance. |
| W | |
| WB | Wet Bulb: A temperature condition reflecting the combined effects of air temperature and moisture content, frequently paired with dry-bulb temperature in ratings and psychrometric analysis. |
| WBT | Wet-Bulb Temperature: The temperature indicated by an evaporatively wetted sensor exposed to airflow, used to determine humidity properties and evaporative-cooling potential. |
| WSHP | Water-Source Heat Pump: A heat pump that exchanges heat with a circulating water loop, enabling distributed zonal equipment to provide heating or cooling. |