2,400+ Definitions
HVAC GLOSSARY
Every HVAC term, acronym, and industry phrase — defined in plain English.
Equipment Room
An equipment room is an enclosed space designed to house…
Equipment Schedule
An Equipment Schedule is a comprehensive table listing all mechanical…
Equipment Selection
Equipment Selection is the process of specifying individual HVAC components…
Equipment Start Up
Equipment Start Up is the systematic process of initially energizing,…
Equipment Startup
Equipment startup is the controlled activation and verification of an…
Equivalent Diameter
The diameter of a round duct that produces the same…
Equivalent Length
Equivalent length is a method of expressing the pressure drop…
Equivalent Round Diameter
Equivalent Round Diameter (ERD) is a calculated measurement that converts…
ERV (Energy Recovery Ventilator)
An Energy Recovery Ventilator (ERV) provides controlled fresh air ventilation…
ESPI Standard
The Energy Services Provider Interface (ESPI) Standard is a data…
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…
Evaporating Temperature
The saturation temperature of the refrigerant inside the evaporator coil…
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…
Evaporative Cooling
A process that reduces air dry-bulb temperature by evaporating water…
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…
Evaporator Fan Delay Relay
A control relay that holds evaporator fans off for a…
EWT (Entering Water Temperature)
The temperature of the fluid as it enters the heat…
Excess Air
The amount of combustion air supplied beyond the stoichiometric quantity…
Exfiltration
Exfiltration is the uncontrolled leakage of conditioned indoor air escaping…
Exhaust Air Transfer Ratio
A metric that quantifies how much exhaust air leaks into…
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 Hood Capture Velocity
The air velocity at the open face or at the…
Exhaust Ventilation
Exhaust ventilation removes stale air, moisture, and contaminants from indoor…
Exhaust-Only Ventilation
A ventilation strategy that uses fans only to remove 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…
Expansion Tank Acceptance Volume
The portion of an expansion tank’s total volume that is…
External Wall Insulation
External wall insulation (EWI) is a continuous insulation layer applied…
Extractor
A fitting installed at a branch takeoff that uses turning…
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…
Fail-Safe Position
The predetermined position to which an actuator drives its controlled…
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…