2,400+ Definitions
HVAC GLOSSARY
Every HVAC term, acronym, and industry phrase — defined in plain English.
Standing Pressure Test
A standing pressure test is a procedure used to verify…
Standing Vacuum Test
An extended period, often 15 to 30 minutes or more,…
Staple-Up Radiant
A radiant floor heating installation method where PEX or other…
Start Assist
A start assist is an auxiliary electrical device installed in…
Start Capacitor
An electrolytic capacitor connected in series with the start winding…
State Energy Office
A State Energy Office is the designated state agency responsible…
State of Charge
State of Charge (SoC) is the current amount of energy…
Static Pressure
Static pressure is the force exerted by air against duct…
Static Pressure Check
A static pressure check measures ductwork resistance to airflow, helping…
Static Pressure Test
A static pressure test measures the resistance to airflow within…
Static Regain
The increase in static pressure that occurs when air velocity…
Steady State
Steady state occurs when system properties remain constant over time,…
Steam Boiler
A steam boiler is a closed pressure vessel designed to…
Steam Coil
A steam coil is a heating heat exchanger that transfers…
Steam Plant
A Steam Plant is a centralized heating facility that generates…
Step Down Transformer
A step down transformer reduces high voltage electrical power to…
Step Up Transformer
A step-up transformer increases voltage while proportionally decreasing current, maintaining…
Stoichiometric Combustion
The theoretical ideal condition in which exactly the right amount…
String Inverter
A string inverter is a single centralized device that converts…
Subcooling
Subcooling is the temperature decrease of a liquid refrigerant below…
Subcooling Charging Method
The subcooling charging method optimizes refrigerant charge by measuring the…
Subcooling Check
A subcooling check measures the temperature drop of refrigerant liquid…
Subcooling Thermometer Set
A pair of thermocouple probes and an electronic readout used…
Subcritical CO2
Subcritical CO2 operation maintains system pressure and temperature below the…
Suction Group
A set of refrigerated fixtures or cases that operate at…
Suction Line
The suction line is the refrigerant piping that connects the…
Suction Line Accumulator
A suction line accumulator is a refrigerant management device installed…
Suction Line Filter Drier
A bidirectional or suction-specific drier installed temporarily or permanently in…
Summer Design Dry Bulb
Summer design dry bulb temperature is the peak outdoor air…
Summer Design Wet Bulb
Summer design wet bulb temperature represents the humidity level coinciding…
Superheat
Superheat is the temperature increase of a vapor above its…
Superheat Charging Method
The superheat charging method adjusts refrigerant charge by measuring temperature…
Superheat Check
A superheat check measures the temperature rise of refrigerant vapor…
Superheat Controller
An electronic device that monitors suction line temperature and pressure…
Supermarket Refrigeration
Supermarket refrigeration encompasses integrated systems of reach-in cases, open-air display…
Supervisory Control
Supervisory Control is an automated system function that monitors, adjusts,…
Supplemental Heat Lockout
A control feature that prevents electric resistance or fossil fuel…
Supply Air Diffuser
A supply air diffuser is a terminal outlet device that…
Supply Duct
Supply ducts deliver conditioned air from the furnace or air…
Supply Ventilation
Supply ventilation mechanically introduces filtered outside air into conditioned spaces…
Supply-Only Ventilation
A ventilation strategy that mechanically forces outdoor air into the…
Surface Sampling
Surface sampling collects mold samples directly from building materials and…
Surface Temperature Uniformity
A measure of how evenly heat is distributed across a…
Surface Thermocouple
A flat or curved probe designed to press firmly against…
Surge (Centrifugal Compressor)
An unstable operating condition in a centrifugal chiller compressor where…
Sweat Fitting
Sweat fittings are soldered copper connections where solder metal flows…
Swimming Pool HVAC
Swimming pool HVAC systems manage temperature, humidity, and air quality…
System Commissioning
System commissioning is a quality-focused process for verifying and documenting…