Accessory List

Glossary

Variable Frequency Drive: A device that varies the voltage

to an electric motor to vary the speed of the motor (also called

a speed drive.)

VDC: Volts direct current.

Velocity Pressure: The pressure caused by the air being in

motion and has a direct relation to the velocity of the air.

Wet-Bulb Temperature: Air temperature as measured by a

wet-bulb thermometer and which is lower than dry-bulb

temperature (for all cases except when the air is saturated) in

inverse proportion to the humidity.

Zone: A space or group of spaces within a building with

heating and/or cooling requirements sufficiently similar so that

comfort conditions can be maintained throughout by a single

controlling device.

Zone Control: A control process in which a building is

divided into different areas (zones). Each zone can be

controlled independently.

Zoned Reheat: Provides zone or space control for areas of

unequal loading and simultaneous heating or cooling of

perimeter areas with different exposures. Heat is added as a

secondary simultaneous process to preconditioned (cooled,

humidified, etc.) primary air or recirculated room air.