HVAC and BEMS

HVAC term for controls that vary airflow through an air outlet, inlet, or duct.  A damper position may be immovable, manually adjustable, or part of an automated control system.

A device that controls the opening and closing of a damper in HVAC systems.

A deadband (sometimes called a neutral zone) is an area of a signal range or band where no action occurs (the system is dead).  Deadband is used in voltage regulators and other controllers. The purpose is common, to prevent oscillation or repeated activation-deactivation cycles (called "hunting" in proportional control systems).

A unit for measuring the extent that the outdoor daily average temperature (the mean of the maximum and minimum daily dry-bulb temperatures) falls below (in the case of heating, see Heating Degree Day), or falls above (in the case of cooling, see Cooling Degree Day) an assumed base temperature, normally taken as 18.333°C (65°F), unless otherwise stated.  One degree day is counted for each degree below (for heating) or above (in the case of cooling) the base, for each calendar day on which the temperature goes below or above the base.

The product of one (1) hour, and usually the number of degrees Fahrenheit the hourly mean temperature is above a base point (usually 18.333°C / 65°F); used in roughly estimating or measuring the cooling load in cases where processes heat, heat from building occupants, and humidity are relatively unimportant compared to the dry-bulb temperature.

A device for reducing the level of humidity in a room or home.

Components of the ventilation system that distribute and return air to promote air circulation in the occupied space.  As used in this document, supply air enters a space through a diffuser or vent and return air leaves a space through a grille.

Used to refer to more than one concept.  It can refer to discrete-time signals that have a discrete number of levels, for example, a sampled and quantified analogue signal, or to the continuous-time waveform signals in a digital system, representing a bit-stream.

Direct Digital Control (DDC) is the automated control of a condition or process by a digital computer.  DDC is often to control HVAC devices such as valves via microprocessors using software to perform the control logic.  Such systems receive analogue or digital inputs from the sensors and devices installed in the HVAC system and, according to the control logic, provide analogue or digital outputs to control the HVAC system devices.

Refers to the more common refrigerant evaporator coil.  The evaporator is in direct contact with the air stream, so the cooling coil of the airside loop is also the evaporator of the refrigeration loop.  The term "direct" refers to the position of the evaporator with respect to the airside loop.   This coil usually has direct expansion valve connected to the coil distributor.