Glossary of Terms

alternating current
device, either electrically, pneumatically, or hydraulically operated, that acts as a motor to change the position of movable devices such as valves or dampers
Air Flow:
The distribution or movement of air.
Air Handler:
The portion of the central air conditioning or heat pump system that moves heated or cooled air throughout a buildings ductwork.
A transducer designed to transmit or receive microwaves

CFM (Cubic Feet per Minute):

The abbreviation for cubic feet per minute, commonly used to measure the rate of air flow in an air conditioning system.
The pump that moves the refrigerant from the indoor evaporator to the outdoor condenser and back to the evaporator again. The compressor is often called “the heart of the system” because it circulates the refrigerant through the loop.
Convection Cooking:
Use of a heating appliance (convection oven) which operates by air convection currents circulating through the body of the appliance, and across its heating element in order to cook food.


A movable plate that opens and closes to control airflow. Dampers are used effectively in zoning to regulate airflow to certain rooms and to balance preassure in a building.
Pipes or channels that carry air throughout a building.

Evaporator Coil:

Part of the air conditioner or refrigeration unit that is indoors. The evaporator coil cools and dehumidifies the air by converting liquid refrigerant into a gas, which absorbs the heat from the air. The warmed refrigerant is then carried through a tube to the outdoor unit.

Heating Element:
Converts electricity into heat through the process of Joule heating. Electric current through the element encounters resistance, resulting in heating of the element. Most heating elements use Nichrome 80/20 (80% nickel, 20% chromium) wire, ribbon, or strip. Nichrome 80/20 is an ideal material, because it has relatively high resistance and forms an adherent layer of chromium oxide when it is heated for the first time. Material beneath the wire will not oxidize, preventing the wire from breaking or burning out.

Acronym used for Heating, Ventilation, and Air Conditioning.


A high-powered vacuum tube that generates microwaves using the interaction of a stream of electrons with a magnetic field.
A hydraulic manifold is a component which regulates fluid flow between pumps and actuators and other components in a hydraulic system.
A a small computer on a single integrated circuit consisting internally of a relatively simple CPU, clock, timers, I/O ports, and memory.
Package Unit:
A self-contained heating and/or air conditioning system.

R 410A/Puron©:

Puron© refrigerant is an environmentally sound refrigerant designed not to harm the earth’s ozone layer. Federal law requires that all manufacturers phase out ozone depleting refrigerants in the next few years. Puron© is approved by the United States EPA as a replacement for Freon R22.
Refrigerant Lines:
Set of two copper lines connecting the outdoor unit and the indoor unit. They should be insulated.

Solenoid Valve
A solenoid valve is an electromechanical valve for use with liquid or gas. The valve is controlled by an electric current through a solenoid coil. Solenoid valves may have two or more ports: in the case of a two-port valve the flow is switched on or off; in the case of a three-port valve, the outflow is switched between the two outlet ports. Multiple solenoid valves can be placed together on a manifold.
A loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it.
Split System:
Refers to an air conditioner or heat pump that has components in two locations. Usually, one part of the system is located inside (evaporator coil) and the other is located outside (condenser coil).


A unit of measurement for cooling capacity. One ton = 12,000 BTU’s per hour.

Variable Speed:

A motor that automatically adjusts the flow of warm or cool air for ultimate comfort.


A linear structure that conveys microwaves between its endpoints