A programmable thermostat is a device that allows you to automatically control your heating and cooling systems based on a schedule that you set. It enables you to set specific temperatures for different times of the day and night, helping to improve energy efficiency and comfort. For example, you can program it to keep your...

PSC stands for "Permanent Split Capacitor," which is a type of motor commonly used in HVAC systems for fans and pumps. These motors run on AC voltage and operate at a fixed speed, sometimes offering two or three preset speed options. However, they are generally less energy-efficient compared to newer motor technologies, as they lack...

PSI refers to "Pounds Per Square Inch," which is a unit of pressure measurement. It describes the amount of force applied over one square inch of area. In HVAC systems, PSI is commonly used to measure the pressure of refrigerants in different parts of the system, as well as the pressure in compressed air systems...

PSIA stands for pounds per square inch absolute. It is a unit of pressure measurement that includes atmospheric pressure in its calculation. Unlike PSIG (pounds per square inch gauge), which measures pressure relative to atmospheric pressure, PSIA measures the total pressure, including the atmospheric pressure at sea level (14.7 psi at standard atmospheric conditions). For...

PSIG stands for "pounds per square inch gauge," which is a measurement of pressure. It represents the pressure of a system relative to atmospheric pressure. In HVAC systems, PSIG is often used to measure the pressure inside refrigerant lines or tanks. If the pressure reading is zero PSIG, it means the pressure inside the system...

Pulse Width Modulation (PWM): A technology used to control the speed of motors, such as those in HVAC systems, by rapidly switching the power on and off. In HVAC systems, PWM is often associated with ECM (Electronically Commutated Motors). This method allows for precise control of fan speeds, enabling the system to adjust airflow as...

A purge unit is a device used in chiller systems to remove non-condensable gases, such as air or other impurities, that can accumulate within the refrigeration system. These gases can impair system efficiency by reducing heat transfer and increasing pressure. The purge unit captures and expels these unwanted gases from the system, ensuring the chiller...

PVC, or polyvinyl chloride, is a durable and versatile plastic commonly used in HVAC systems for various purposes, such as drain lines, vent pipes, and ductwork. It is lightweight, resistant to corrosion, and cost-effective, making it a practical choice for safely transporting air, water, or condensate without degrading over time.

PWM (Pulse Width Modulation) is a technique used in HVAC systems to control the speed of devices like fans or compressors by adjusting the power supplied to them. Instead of running at full power all the time, the motor receives a series of rapid on/off pulses, with the duration of the "on" time determining the...

R-22 Refrigerant: A chemical compound (also known as Freon) that was commonly used as the refrigerant in residential and commercial air conditioning systems for several decades. However, due to its harmful effects on the ozone layer, its production and use have been gradually phased out under the Montreal Protocol and U.S. EPA regulations. Systems using...