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
Total Volatile Organic Compounds
Total volatile organic compounds (TVOCs) is the combined concentration of…
Trane Trace
Trane Trace is a comprehensive whole-building energy modeling software developed…
Transcritical CO2
Transcritical CO2 operation occurs when the refrigerant pressure exceeds the…
transcritical cycle
A refrigeration cycle in which the high-side pressure exceeds the…
Transfer Grille
A transfer grille is an opening with a fixed or…
Transformer
A transformer is an electrical device that converts high-voltage power…
Transformer VA Rating
The apparent power rating of a transformer expressed in volt-amperes,…
Transient State
Transient state describes system conditions where properties change with time…
Trend Analysis BAS
Trend analysis in Building Automation Systems (BAS) is the examination…
Trend Log
A BAS function that records time-stamped values of selected analog…
Trigeneration
Trigeneration is an advanced energy system that simultaneously produces electricity,…
Trim and Respond
Trim and Respond is a control strategy that optimizes chiller…
Trim and Respond Logic
A supervisory control algorithm used in variable-flow systems where a…
Triple Evacuation
Triple evacuation is an advanced evacuation method that removes moisture…
True RMS Meter
A True RMS (Root Mean Square) meter accurately measures electrical…
Tube Spacing
The center-to-center distance between adjacent tubing runs in a radiant…
Tubular Heat Exchanger
A heat exchanger design using round or oval tubes through…
Tunnel Ventilation
Tunnel ventilation systems remove vehicle exhaust, smoke, and hazardous gases…
Turbulent Airflow
Turbulent airflow consists of random, non-directional air movement created by…
Turndown Ratio
The ratio of maximum to minimum firing rate at which…
Turning Vane
A turning vane is an internal curved or angled blade…
TVOC
TVOC represents the total mass concentration of volatile organic compounds…
Twin Rotary Compressor
A compressor type using two offset rotary elements on a…
Two Phase Immersion
Two Phase Immersion Cooling uses dielectric fluids that boil at…
Two Pipe System
A two-pipe system is a hydronic HVAC distribution configuration that…
Two Stage Furnace
A two-stage furnace is a gas-fired heating appliance equipped with…
Two Way Valve
A two-way valve has one inlet and one outlet port,…
Two-Pipe Changeover System
A hydronic distribution system that uses a single pair of…
Two-Position Control
The simplest control mode, in which an output device such…
Two-Stage Vacuum Pump
A vacuum pump with two compression stages in series that…
TXV
A thermostatic expansion valve (TXV) is a precision refrigerant metering…
TXV (Thermostatic Expansion Valve)
A Thermostatic Expansion Valve (TXV, also TEV) is a refrigerant…
Type B Vent
Type B vent is a double-wall metal pipe designed for…
Type I Certification
Type I Certification authorizes technicians to service small appliances containing…
Type I Hood
A Type I hood is a grease-capturing exhaust hood specifically…
Type II Certification
Type II Certification authorizes technicians to service large appliances and…
Type II Hood
A Type II hood is a ventilation hood designed for…
Type III Certification
Type III Certification authorizes technicians to service high-pressure air conditioning…
Typical Meteorological Year
Typical Meteorological Year (TMY) represents a complete 12-month weather dataset…
U Value
U Value measures the overall rate of heat transfer through…
UEF
UEF stands for Uniform Energy Factor, the standardized efficiency rating…
UL 1995
UL 1995 is the safety standard for commercial and industrial…
UL 207
UL 207 is a safety standard published by Underwriters Laboratories…
UL 303
UL 303 is a safety standard published by Underwriters Laboratories…
UL 4811
UL 4811 is the safety standard for solar photovoltaic (PV)…
UL 60335-2-40
UL standard harmonized with the international IEC standard covering the…
ULPA Filter
ULPA (Ultra-Low Penetration Air) filters capture 99.99% of particles at…
Ultrasonic Leak Detector
An ultrasonic leak detector identifies refrigerant leaks by sensing the…