2,400+ Definitions
HVAC GLOSSARY
Every HVAC term, acronym, and industry phrase — defined in plain English.
Specific Heat
Specific heat is the amount of thermal energy required to…
Specific Volume
Specific volume is the volume occupied by one pound of…
Spiral Duct
Spiral duct is a round ductwork constructed by spirally winding…
Split System
A split system is an HVAC configuration that divides its…
Split System Installation
Split system installation involves connecting an outdoor condenser unit to…
Spore Trap
A spore trap is a passive or active air sampling…
Spot Exhaust
Spot exhaust is a localized ventilation system that removes moisture,…
Spot Monitoring
Spot monitoring is the collection of air quality measurements at…
Spray Foam Insulation
Spray foam insulation is a polyurethane or polyisocyanurate material applied…
Spring Isolator
A spring isolator is a mechanical device using compressed steel…
Spring Return Actuator
A spring return actuator uses an internal spring mechanism to…
Spring Startup
Spring Startup is the pre-season service performed before cooling season…
SREC
An SREC (Solar Renewable Energy Certificate) is a tradable credit…
Stack Effect
The stack effect describes the natural movement of air through…
Stainless Steel Pipe
Stainless steel pipe is a corrosion-resistant tubing made from steel…
Standby Mode
Standby Mode is a low-energy operational state where HVAC components…
Standing Pilot
A standing pilot is a small, continuously burning flame that…
Standing Pressure Test
A standing pressure test is a procedure used to verify…
Start Assist
A start assist is an auxiliary electrical device installed in…
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…
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…
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…
Subcritical CO2
Subcritical CO2 operation maintains system pressure and temperature below the…
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…
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…
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,…
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…
Surface Sampling
Surface sampling collects mold samples directly from building materials and…