2,400+ Definitions

HVAC GLOSSARY

Every HVAC term, acronym, and industry phrase — defined in plain English.

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ETL Listed
ETL Listed indicates that equipment has been tested and certified…
EUI
EUI is the abbreviation for Energy Use Intensity, a key…
Evacuated Tube Collector
An evacuated tube collector uses rows of glass tubes with…
Evacuation
Evacuation is the process of removing air and moisture from…
Evaporation
Evaporation is the phase change process where liquid converts to…
Evaporative Condenser
An evaporative condenser combines refrigerant cooling with water evaporation to…
Evaporative Cooler
An evaporative cooler, also called a swamp cooler, reduces air…
Evaporator Coil
The evaporator coil is the indoor heat exchange component of…
Evaporator Coil Cleaning
Evaporator Coil Cleaning is the removal of dust, mold, and…
Exfiltration
Exfiltration is the uncontrolled leakage of conditioned indoor air escaping…
Exhaust Damper
An exhaust damper is a mechanical device installed within an…
Exhaust Fan
An exhaust fan is a mechanical ventilation device designed to…
Exhaust Hood
An exhaust hood is a ventilation system component that removes…
Exhaust Ventilation
Exhaust ventilation removes stale air, moisture, and contaminants from indoor…
Expansion Loop
An expansion loop is a U-shaped or S-shaped pipe section…
Expansion Tank
An Expansion Tank is a sealed vessel that accommodates water…
External Wall Insulation
External wall insulation (EWI) is a continuous insulation layer applied…
F Gas Regulation
The F Gas Regulation is the European Union’s framework for…
Face and Bypass Damper
A face and bypass damper is an airflow control arrangement…
Face Velocity
Face velocity is the speed of air moving across the…
Fall Startup
Fall Startup is the pre-season service performed before heating season…
Fan Affinity Laws
Fan Affinity Laws describe how centrifugal fan performance changes with…
Fan Airflow
Fan airflow is the volume of air moved by a…
Fan Balancing
Fan balancing is the process of correcting mass distribution on…
Fan Blade Cleaning
Fan blade cleaning is the maintenance procedure of removing accumulated…
Fan Coil
A fan coil unit (FCU) is a localized air handling…
Fan Coil Unit
A Fan Coil Unit (FCU) is a self-contained HVAC terminal…
Fan Curve
A fan curve is a manufacturer-provided graph plotting the relationship…
Fan Direction
Fan direction refers to the rotational orientation of ceiling fan…
Fan Efficiency
Fan efficiency measures the ratio of useful air power output…
Fan Laws
Fan laws are mathematical relationships describing how fan performance changes…
Fan Noise
Fan noise is the audible sound produced by a fan…
Fan Powered VAV
A Fan Powered Variable Air Volume (FPVAV) terminal unit is…
Fan Relay
A fan relay is an electromagnetic switching device that controls…
Fan Speed
Fan speed refers to the rotational velocity of fan blades,…
Fan Stall
Fan stall occurs in axial fans when airflow separates from…
Fan Static Pressure
Fan static pressure is the pressure component that overcomes system…
Fan Surge
Fan surge is an unstable operating condition where the fan…
Fan Total Pressure
Fan total pressure is the complete pressure rise generated by…
Fan Velocity Pressure
Fan velocity pressure is the kinetic energy component of airflow,…
Fan Vibration
Fan vibration refers to mechanical oscillations transmitted through the fan…
Far UV Light
Far UV light, also called far ultraviolet or far-UVC, refers…
Fault Detection
Fault detection is the identification of equipment malfunction, sensor failure,…
Fault Isolation
Fault isolation is the process of identifying the specific component,…
Federal Investment Tax Credit
The Federal Investment Tax Credit (ITC) is a federal tax…
Federal Minimum Efficiency
Federal Minimum Efficiency refers to the lowest allowable energy performance…
Federal Standard 209E
Federal Standard 209E was the predecessor to ISO 14644-1, establishing…
Federal Tax Deduction 179D
Section 179D of the Internal Revenue Code allows building owners…