2,400+ Definitions
HVAC GLOSSARY
Every HVAC term, acronym, and industry phrase — defined in plain English.
Variable Flow
Variable flow hydronic systems adjust circulation pump speed and water…
Variable Frequency Drive
A Variable Frequency Drive (VFD) is an electronic controller that…
Variable Frequency Drive (VFD)
A Variable Frequency Drive (VFD) is an electronic controller that…
Variable Geometry Diffuser
An adjustable vane ring at the outlet of a centrifugal…
Variable Pitch Fan
A variable pitch fan (VPF) is an axial fan designed…
Variable Primary Flow
A chilled water plant design in which the chilled water…
Variable Refrigerant Flow
Variable Refrigerant Flow (VRF) is an advanced HVAC technology that…
Variable Setpoint
A variable setpoint is a target temperature that automatically adjusts…
Variable Speed Drive
A variable speed drive (VSD) is an electronic controller that…
Variable Speed Injection Mixing
A method of controlling supply water temperature in a radiant…
Variable Speed Motor
A variable speed motor (also called an ECM — Electronically…
Variable Torque Load
A variable torque load is a mechanical resistance that increases…
Variable-Base Degree Days
Heating or cooling degree days calculated using a base temperature…
VAV Box
A Variable Air Volume (VAV) box is an HVAC terminal…
Velocity Pressure
The pressure associated with the kinetic energy of moving air,…
Velometer
A direct-reading airflow instrument historically used to measure air velocity…
Ventilation
Ventilation is the controlled exchange of indoor and outdoor air,…
Ventilation Effectiveness
Ventilation effectiveness measures how efficiently a ventilation system removes contaminants…
Ventilation Rate Procedure
The Ventilation Rate Procedure is a prescriptive ASHRAE 62.1 method…
Verification Testing
Verification testing in HVAC refers to the systematic process of…
Vertical Loop Field
A geothermal ground heat exchanger configuration where boreholes are drilled…
Very High Pressure Category
The Very High Pressure Category includes systems operating at pressures…
VFD
A Variable Frequency Drive (VFD) is an electronic device used…
VFD Carrier Frequency
The switching frequency of the insulated gate bipolar transistors in…
Vibration Analysis Maintenance
Vibration analysis maintenance measures mechanical vibration in compressors, motors, and…
Vibration Analyzer
A vibration analyzer is a sophisticated diagnostic instrument that measures…
Vibration Isolation Pad
A vibration isolation pad is a resilient material placed under…
Vibration Isolator
A vibration isolator is a mechanical device engineered to reduce…
Vibration Meter
A vibration meter is a portable instrument that measures mechanical…
Virtual Islanding
Virtual islanding is a control strategy that allows a grid-connected…
Virtual Net Metering
Virtual net metering allows customers to receive bill credits for…
Virtual Power Plant
A virtual power plant is a network of distributed energy…
Visible Transmittance
The fraction of visible light in the solar spectrum that…
VOC
Volatile organic compounds (VOCs) are carbon-containing chemicals that evaporate at…
VOC Monitor
A VOC monitor detects volatile organic compounds in indoor air,…
Volatile Organic Compound
Volatile Organic Compounds (VOCs) are carbon-containing chemicals that evaporate at…
Volatile Organic Compound Offgassing
The release of gaseous chemicals from solid or liquid materials…
Volatile Organic Compound Sources
Volatile Organic Compound (VOC) Sources are materials and products that…
Volt
A volt (V) is the unit of electrical potential difference…
Volume Damper
A volume damper is a manually or electronically adjustable valve…
VRF System
VRF (Variable Refrigerant Flow) is a sophisticated HVAC technology used…
Walk In Cooler
A walk-in cooler is a large, insulated refrigerated room that…
Walk In Freezer
A walk-in freezer is an insulated, temperature-controlled room that maintains…
Walk-In Cooler
A large insulated room maintained at above-freezing temperatures, typically 35…
Wall Furnace
A wall furnace is a self-contained, vented heating appliance designed…
Wall Insulation
Wall insulation refers to materials installed within wall cavities, externally,…
Wall Sleeve
A wall sleeve is a metal or plastic tube installed…
Wall-Mount Indoor Unit
The most common ductless indoor unit type, which mounts high…