United CoolAir Glossary
Reverse flow of air / gases down the chimney of a vented combustion appliance.
Pressure in low side of refrigerating systems; also called suction pressure or low-side pressure.
Fluid opening/closing such as a gauge opening; to seat the joint where the valve stem goes through the valve body.
Plate or vane used to direct movement of a fluid within a confined area.
The point at which the heating capacity of a heat pump is equal to the heat losses of the structure it is heating.
The process of adjusting the flow of air in a duct system, or water flow in a Hydronic system.
Ball Check Valve
A check valve that uses a ball to permit flow in one direction only.
Unit of pressure. One bar equals .9869 atmosphere(approximately one atmosphere, 14.51 psi).
Instrument for measuring atmospheric pressure.
Force or weight exerted by the atmosphere. Standard barometric pressure is taken as 29.92 inches of mercury or 14.7 pounds per square inch.
A rubber-like, continuous loop placed between two or more pulleys to transfer rotary motion.
In stream of liquid, the sum of elevation head, pressure head, and velocity remains constant along any line of flow, provided no work is done by or upon liquid on course of its flow; decreases in proportion to energy lost in flow.
Temperature regulating or indicating device that works on the principle that two dissimilar metals with unequal expansion rates, welded together, will bend as temperatures change.
Valve with small opening inside that permits a minimum fluid flow when valve is closed.
Slowly reducing the pressure of liquid or gas from a system by opening a valve slightly.
A mixture of various refrigerants.
An air handling/movement device.
The temperature of a liquid at which it changes to a gas under a pressure of 14.7 psia (101.3 kPa).
Temperature at which a fluid changes from a liquid to a gas.
Boyle's Law: Law of Physics
The volume and pressure of a gas vary inversely if the temperature remains the same. Example: If the pressure is doubled on a quantity of gas, its volume is reduced one-half. If the volume is doubled, gas has its pressure reduced by one-half. Brazing: Method of joining metals with nonferrous (without iron) filler using heat between 800°F (427°C) and the melting point of base metals.
Water saturated with a chemical such as salt. Used for transmission of heat without a change in its state.
British thermal unit (Btu)
Quantity of heat required to raise temperature of one pound of water one degree fahrenheit.