Glossary of Applied Air HVAC Terminology

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Damper
A device that is located in ductwork to adjust air flow.
DB
Dry Bulb Temperature
dB (Decibel)
A decibel describes the relative loudness of a sound on a logarithmic scale.
DDC
Direct Digital Control is the method of activating, deactivating, and monitoring the control points in an HVAC system using computer-logic and microprocessors.  This method of control includes the software that provides the instructions to the HVAC unit components and directs their action based upon the input from a variety of sensor types.  DDC controls can be embedded in individual pieces of equipment, can be a total unit controller, or can be a remote computer that communicates unit operational commands via a network.
Dehumidification
The reduction of water vapor in air by cooling the air below the dew point; removal of water vapor from air by chemical means, refrigeration, etc.
Dew point
The exact temperature at which moisture begins to form.
Direct Gas-Fired Heater
The burner fires directly in the air stream being heated, rather than through a heat exchanger. 100% of available BTUs are delivered to the heated space because no flue or heat exchanger is required. This results in no wasted energy.
DOAS
DOAS stands for Dedicated Outdoor Air System.  A DOAS piece of HVAC equipment is designed specifically to filter, temper, and control the amount of outside air that enters a building.  DOAS equipment is typically used to provide the amount of ventilation air required by the building codes to satisfy the fresh air requirements for the building occupants.  A DOAS unit is only a component of a much larger system.  The remainder of the system is designed to satisfy the sensible cooling load of the building without concern for the outside air requirement.
DOE (Department of Energy)
The Department of Energy is a federal agency in charge of setting industry efficiency standards and monitoring the consumption of energy sources.
Duct
A pipe or closed conduit made of sheet metal, fiberglass board, or other suitable material used for conducting air to and from an air handling unit.