U-value
Represents the heat leakage from one side of a wall to the other.
Ultrasonic
Having a frequency above the range of human hearing.
Ultraviolet
Invisible radiation waves with frequencies shorter than wave lengths of visible light and longer than X rays.
Unitary system
A factory assembled heating/cooling system in one package and usually designed for conditioning one space or room.
Universal motor
Electric motor that will operate on either ac or dc.
Unloader
A device that allows for easier compressor start-up by temporarily reducing high-side pressure at the cylinder head.
Upflow furnace
A furnace in which air is forced up through the furnace from the bottom.
Urethane Foam
Type of foam insulation that is placed between the inner and outer walls of a container.