2,400+ Definitions
HVAC GLOSSARY
Every HVAC term, acronym, and industry phrase — defined in plain English.
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…
System Curve
A graphical representation of the relationship between flow rate and…
System Curve Fan
A system curve is a graph representing the static pressure…
System Decommissioning
System decommissioning in HVAC refers to the planned, systematic process…
System Diagnosis
System diagnosis is the systematic evaluation of HVAC equipment performance…
System Flush
A system flush is the process of circulating a specialized…
System Selection
System Selection is the decision-making process for choosing the overall…
System Startup Checklist
A system startup checklist is a documented procedure verifying all…
System Ventilation Efficiency
A multiplier used in ASHRAE 62.1 multiple-zone recirculating system calculations…
System Weigh In
System Weigh In is a comprehensive verification process performed on…
Systems Manual
A Systems Manual is a comprehensive reference document that contains…