The term HVAC control refers to a system of automated climate control in buildings. HVAC is an acronym for heating, ventilation, and air conditioning, and encompasses the complete internal climate manipulation of any building or space. HVAC control systems typically consist of computerized networks in large buildings and stand alone, single controller systems in homes or smaller venues. Both constantly monitor and adjust the internal climate of a building according to preset parameters measured against the input of sensors placed throughout the space. These climate control systems often include peripheral functionality such as fire protection, lighting, and security and may also feature diagnostic and remote control capabilities.
Any space served by one or more central climate systems usually needs a centralized mechanism which monitors and adjusts the internal climate if needed. HVAC control systems fulfill this requirement by monitoring the input of sensors placed in relevant locations around the space and comparing them to known parameters. These parameters are user defined and stored in the controller program and serve as a benchmark for system operation. Should the air flow or temperature in a certain area or zone of the building deviate from those parameters, the HVAC control system will automatically intervene to rectify the situation.
This intervention may come in the form of electronic signals sent to the control panels of fans, air conditioners, and heaters or to pneumatic or hydraulic controllers operating vents or valves. Electronic messages can tell the relevant equipment to turn on or off, increase or decrease temperature, and divert, restrict or shut off air, water, or steam flow. In very large facilities, there may be several parent HVAC control points each controlling several smaller systems. In homes or small buildings, HVAC functionality is typically confined to a single controller station.
HVAC control terminals are generally driven by direct digital control (DDC) software that can be programmed with user-specific data. Depending on the sophistication of the system, users can define a large range of climatic criteria for their environment. These include identifying zones or specific areas within the space, controlling temperatures and air flow, and setting specific times for heating or cooling cycles in those specific areas. Increasing sophistication in HVAC control technology and demand for one-stop solutions have also seen the inclusion of lighting control, security system monitoring, and fire protection included in these applications. Another recent development is remote access functionality which allows users to initiate HVAC controls via Ethernet connections.