AU FM COVID-19 FAQ

What types of Heating, Ventilation and Air Conditioning (HVAC) systems does Auburn University have on campus?

Auburn University buildings generally are conditioned by one or a combination of three types of HVAC systems:

  1. Fan coil units
  2. Central air handling systems
  3. Localized refrigerant-based systems

Cooling is provided from one of the following sources:

  1. Central campus chilled water system (consisting of four chilled water plants)
  2. Water chillers located at the building
  3. Refrigerant based systems (similar to a residential HVAC unit)

Heating is provided from one of the following sources:

  1. Central campus hot water system (consisting of three hot water plants)
  2. Central campus steam system (consisting of one steam plant)
  3. Water heater/boiler system located at the building
  4. Electrical heating coils

Note: Exhaust is provided in restrooms to remove odors and helps to maintain a slightly positive building pressure.

FAN COIL UNIT (FCU):

A fan coil unit consists of a fan and at least one water coil located in the unit. FCUs have air filters, a water coil(s) for heating and cooling the air, and a supply fan for forced air circulation through the unit and into the space. Water coils in units are like a car radiator that either heat or cool the air depending on the water temperature in the coil. FCUs are generally located within the space they are conditioning; however, they may be located above ceilings and supply air through air ducts. Outside (fresh) air may be introduced through the FCU if the unit is located along an exterior wall. FCUs may be either two-pipe or four-pipe variety. A two-pipe FCU will only be able to heat in cold weather and cool in hot weather. A four-pipe FCU will be able to heat or cool the air at any time of year.

Below are schematic diagrams of each type of FCU.

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CENTRAL AIR HANDLING SYSTEMS:

Central air handling systems are those that consist of one or more air handling units which filter, cool and heat the air then distribute it to occupied spaces via ductwork. Air is typically recirculated from the spaces back to the air handling unit through ceiling mounted air return registers located in each space. The return air is mixed with outside (fresh) air, filtered and cooled in the air handling unit. The cooled supply air is supplied to the building through ductwork.

The four main types of central air handing systems found on campus are listed below along with their operating characteristics:

  1. Variable Volume Reheat Systems – varies the volume of air delivered to each space and heating is accomplished at terminal units with a heating coil and provides multiple temperature control zones on each air handler.
  2. Constant Volume Reheat Systems – maintains a constant volume of air delivered to each space and heating is accomplished at terminal units with a heating coil and provides multiple temperature control zones on each air handler.
  3. Constant Volume Single Zone System – maintains a constant volume of air delivered to each space and heating is provided at the air handler and only one temperature control zone is possible with each air handler.
  4. Constant Volume Multi-Zone Systems – maintains a constant volume of air delivered to each space and heating is provided at the air handler and provides multiple temperature control zones on each air handler.

Below are schematic diagrams of each type of central air handling system.

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LOCALIZED REFRIGERANT-BASED SYSTEMS:

Some of these units are like the heating and cooling system you have in your home. Some, however, are much larger and operate like the constant volume single zone system noted above but use a refrigerant to provide cooling and heating instead of water. These systems generally deliver a constant volume of air and provide a single temperature control zone. Ductless HVAC systems also fall into this category. Ductless systems as their name implies, have an indoor unit that mounts directly in the space being conditioned. These units are similar to FCUs but use refrigerant instead of water to cool or heat the air.

Below are schematic diagrams of a refrigerant-based systems.

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Last Updated: December 10, 2020