Static pressure refers to the resistance or opposition to airflow within a heating, cooling, or ventilation system's ductwork and components. It measures the force needed to push or pull air through the system, including obstacles like filters, registers, bends, and dampers. Proper static pressure is essential for the efficiency and performance of HVAC systems; too...

The process of lowering the temperature of the liquid refrigerant below its condensing or saturation temperature. This ensures that the refrigerant remains fully in liquid form as it moves through the system, which improves efficiency and prevents gas bubbles from forming that could harm the system’s performance. Subcooling is vital for maintaining optimal cooling capacity...

The pressure measured in the low-pressure side of a refrigeration or air conditioning system, specifically in the suction line where the refrigerant enters the compressor in its gaseous state. Suction pressure indicates how well the system is pulling refrigerant through the evaporator coil and aids in diagnosing system performance or potential issues.

Superheat refers to the temperature of a vapor above its boiling point (saturation temperature) at a given pressure. In HVAC systems, it specifically describes the difference between the temperature of the refrigerant vapor at the evaporator outlet and the saturation temperature of the refrigerant inside the evaporator. Proper superheat is essential for ensuring that only...

Air that has been conditioned (heated, cooled, filtered, or dehumidified) by the HVAC system and is delivered into the living spaces of a building through ducts or vents to maintain the desired indoor temperature and air quality.

A thermidistat is a device used in HVAC systems that monitors both indoor temperature and humidity levels. It operates by combining the functions of a thermostat (temperature control) and a humidistat (humidity control) into a single unit. This device not only regulates heating and cooling but also adjusts humidity to maintain comfortable and consistent indoor...

A thermistor is a type of electrical resistor whose resistance changes noticeably with temperature. In HVAC systems, thermistors are commonly used as temperature sensors to monitor and control heating, cooling, and airflow. They can detect temperature changes quickly and accurately, which helps the system maintain desired indoor comfort levels by adjusting the equipment as needed.

A thermocouple is a sensor made of two dissimilar metal wires joined at one end, which generates a small voltage when there is a temperature difference between the joined end (called the "hot junction") and the other ends (called the "cold junction" or reference junction). This voltage increases as the temperature difference grows, allowing the...

A thermostat is a device that monitors the temperature inside a space and controls the heating and cooling system to maintain the desired temperature. It uses sensors to detect the current temperature and signals the HVAC system to turn on or off, or adjust its settings, depending on the temperature you have selected. Modern thermostats...

A thermostatic expansion valve (TXV), also called a thermal expansion valve, is a device used in HVAC systems to regulate the amount of refrigerant that enters the evaporator coil. It adjusts the flow of refrigerant based on the superheat—a measure of how much the refrigerant gas has been heated above its boiling point. By doing...