2,400+ Definitions
HVAC GLOSSARY
Every HVAC term, acronym, and industry phrase — defined in plain English.
Double Bundle Condenser
A water-cooled condenser in a chiller containing two separate tube…
Double Effect Absorption
Double effect absorption is an advanced thermodynamic cycle that uses…
Double Suction Riser
A vertical suction line configuration using two pipes of different…
Draft Gauge
A sensitive low-range manometer calibrated in inches or tenths of…
Draft Hood
A draft hood is a metal fitting installed at the…
Draft Inducer
A draft inducer is an electrically powered blower motor located…
Draft Inducer Motor
A draft inducer motor is a small fan motor that…
Draft Measurement
Draft measurement quantifies the pressure difference between a furnace or…
Drain Pan Treatment Tablet
A drain pan treatment tablet is a slow-release chemical pellet…
Drainback System
A drainback system is an active solar heating method where…
Drift Eliminator
A series of baffled or chevron-shaped channels near the air…
Dry Bulb Temperature
Dry bulb temperature is the actual air temperature measured by…
Dry Cooler
A dry cooler is an air-cooled heat exchanger that rejects…
Dual Axis Tracker
Dual axis trackers rotate photovoltaic panels along two axes, following…
Dual Duct System
A dual duct system is a type of central HVAC…
Dual Fuel System
A dual fuel system is an HVAC configuration that combines…
Dual Run Capacitor
A single capacitor canister housing two capacitor sections sharing a…
Dual-Fuel Heat Pump
A system pairing an air-source heat pump with a gas,…
Dual-Input Thermocouple Thermometer
A portable thermometer capable of accepting two thermocouple probes simultaneously…
Duct Access Door
A duct access door is a hinged or removable panel…
Duct Blaster
A calibrated fan and pressure measurement system used to pressurize…
Duct Blaster Test
A Duct Blaster Test is a diagnostic procedure that measures…
Duct Cleaning
Duct cleaning is the process of removing accumulated dust, debris,…
Duct Design
Duct design is the systematic process of planning and sizing…
Duct Elbow
A duct elbow is a fitting used to change the…
Duct Fabrication
Duct fabrication is the custom construction of metal or fiberglass…
Duct Friction
Duct friction refers to the resistance air encounters as it…
Duct Installation
Duct installation is the process of assembling and securing metal…
Duct Insulation
Duct insulation is thermal and acoustic material applied to ductwork…
Duct Leakage
Duct leakage occurs when conditioned air escapes from supply ducts…
Duct Leakage Class
A standardized rating that quantifies how much air leaks through…
Duct Leakage Tester
A duct leakage tester is a pressurized measurement system that…
Duct Liner
Duct liner is an insulation material applied directly to the…
Duct Mastic
Duct mastic is a pliable sealant compound applied to ductwork…
Duct Pressurization
Duct pressurization testing measures the amount of air leaking from…
Duct Reducer
A duct reducer is a sheet metal or fabricated fitting…
Duct Schedule
A Duct Schedule is a tabular document specifying all ductwork…
Duct Sealing
Duct sealing is the process of closing air leaks in…
Duct Sealing Mastic Application
Duct sealing mastic application involves brushing or spraying specialized sealants…
Duct Sizing
Duct sizing is the process of calculating appropriate ductwork dimensions…
Duct Static Pressure Rating
The maximum positive or negative pressure differential a duct system…
Duct System Design
Duct System Design involves sizing and routing air distribution pathways…
Duct Tee
A duct tee is a T-shaped fitting used in HVAC…
Duct Transition
A duct transition is a fabricated fitting within an HVAC…
Duct Velocity
Duct velocity is the speed at which air moves through…
Ductless Installation
A ductless installation involves mounting an indoor wall unit connected…
Ductwork
Ductwork is the network of metal, fiberglass, or flexible conduit…
dV/dt Filter
An output filter added to a VFD to slow the…