2,400+ Definitions

HVAC GLOSSARY

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

All A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A fan curve is a manufacturer-provided graph plotting the relationship…

Fan direction refers to the rotational orientation of ceiling fan…

Fan efficiency measures the ratio of useful air power output…

Fan laws are mathematical relationships describing how fan performance changes…

Fan noise is the audible sound produced by a fan…

Fan Powered VAV

A Fan Powered Variable Air Volume (FPVAV) terminal unit is…

A fan relay is an electromagnetic switching device that controls…

Fan speed refers to the rotational velocity of fan blades,…

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 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 refers to mechanical oscillations transmitted through the fan…

Far UV light, also called far ultraviolet or far-UVC, refers…

Fault Detection

Fault detection is the identification of equipment malfunction, sensor failure,…

Fault Detection and Diagnostics

Automated software algorithms embedded in a BAS or applied as…

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…

A feed-in tariff (FIT) is a government-backed policy that requires…

Fiberglass Filter

Fiberglass filters use spun glass fibers as the primary filtration…

Fill factor (FF) is a percentage expressing the ratio between…

The structured or splash material inside a cooling tower over…

An automatic or manual valve that connects a hydronic system…

Filter bypass occurs when unfiltered air passes around a filter…

Filter Change is the replacement of furnace and air conditioning…

A filter drier is a sealed component in the refrigerant…

Filter Efficiency

Filter efficiency measures the percentage of airborne particles that a…

Filter housing is the structural enclosure that holds and secures…

Filter life is the duration a filter remains effective before…

Filter Pressure Drop

Filter pressure drop is the resistance created by a filter…

A filter rack is the structural housing that holds an…

Filter Replacement

Filter replacement is the process of removing a used filter…

A fin comb is a lightweight hand tool with multiple…

Fin material refers to the metal composition used in heat…

Fin spacing is the distance (measured in fins per inch)…

Fin Tube Radiation

Fin tube radiation refers to heating equipment where multiple fins…

Fin-Tube Baseboard

A hydronic terminal unit consisting of a copper or steel…

A fire damper is a safety device installed in ductwork…

First Air Conditioner

The first air conditioner was invented by Willis Carrier in…

First Hour Rating

First Hour Rating (FHR) measures the total volume of hot…

First Law of Thermodynamics

The First Law of Thermodynamics, also called the law of…

Fixed Plate Heat Exchanger

A stationary core heat recovery device made of parallel plates…

Flame Rectification

A flame-sensing method that exploits the asymmetric electrical conductivity of…

A dangerous condition in which flames escape the combustion chamber…