Description of HVAC systems

Heating, ventilating, and air conditioning (HVAC) of facilities/buildings is accomplished in many ways, depending on the size, configuration, and location of the buildings and the degree of environmental control needed.

Small simple facilities in temperate climates can be heated and cooled with a separate heating and a separate cooling unit or with a combination heating/cooling unit. Larger facilities employ refrigeration systems and heating systems which may consist of several large units or centralized systems. Facility complexes may treat each facility separately or provide a dedicated building to house central refrigeration and heating systems. Depending on the HVAC units or systems employed, air is treated through the use of ducts, coils, fans and dampers. Liquids are moved through pipes by pumps. Gases are moved through pipes or tubing by compressors. Air is moved through ducts by fans. The amount of flow of these fluids is controlled by valves and dampers that can operate manually or automatically. Various types and kinds of filters may be used at different locations for air, gas or liquids. Building air is recirculated, some building air is exhausted, and outside air is introduced in various ways as make-up air. Various energy sources may be used in HVAC systems including oil, natural gas, propane, coal and electricity. Other equipment such as humidifiers, energy savers/economizers, heat exchangers, expansion tanks, air separators, secondary pumping systems and smoke management systems may be employed. HVAC systems may also be connected to fire safety and alarm systems.

1. Typical HVA C An HVAC system is shown in figure 4-1. The system consists of ducts, dampers with actuators, filter, fan, heating coil, cooling coil, piping, valves with actuators, pumps, boiler, chiller, expansion tanks and air separators.
2. Typical heating/chilled water flow control. A typical heating/chilled water flow control through an oil is shown in figure 4-2 and 4-3. The loop consists of a heating/cooling coil, flow control valve, actuator, positioner, temperature sensor, temperature controller and instrument signal to pneumatic signal converter
3. Other HVA C equipment. Paragraph 4-3, General HVAC equipment description and operation, explains the operation of various types of boilers and chillers including the packaged units presented For more information on design, maintenance, testing, instrument calibration and commissioning of HVAC systems see the American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. (ASHRAE): Guideline 1- 1996, The HVAC Commissioning Process, and The American Society of Mechanical Engineers (ASME).