Air conditioners (also referred to as AC) provide thermal and humidity management in spaces, such as industrial facilities and data centers, where temperature and humidity control is necessary. They can be used to supplement HVAC systems, supplying spot or space cooling if existing HVAC is inadequate, or to provide air temperature and humidity control where HVAC is unavailable. 

Air conditioners chill air by passing indoor air over evaporator coils, returning the chilled air to the room and exhausting the heat removed to the outside.

The components of an air conditioner include:

• Evaporator coils are filled with a refrigerant that changes phase from liquid to gas as warm air passes over them.
• A fan or blower returns cooled air to the room.
• A compressor moves the heated gas to the condenser coils, which condense the refrigerant from gas to liquid.
• A fan pushes warm air out the exhaust.

Image credit: ASHRAE

Types of Air Conditioners

In addition to the familiar window-mounted air conditioners, several newer options are well-suited to spaces where a window unit is not feasible.

Ceiling-mount units are available in both suspended and flush-mount configurations. This configuration is particularly useful in computer rooms or other spaces where spot cooling is needed.

Ductless, split unit, and mini-split unit air conditioners are used in spaces that lack ductwork for HVAC systems. With split-unit systems, different rooms can have separate controls. The compressor is outside the space, reducing ambient noise.

Enclosure units are designed specifically for cooling enclosures that contain electronic equipment. Find additional information about enclosure air conditioners here.

Portable air conditioners are built with wheels, allowing the user to move as needed. Intake and exhaust hoses must be placed outside a window, limiting this type of air conditioner's use to spaces with a window. 

Specifications

All air conditioners share basic specifications, regardless of physical form.

Cooling capacity (kilowatts, tons, or BTU/hour): Manufacturers generally provide sizing software and/or services to assist in determining cooling loads

Electrical specifications:

• Operating voltage in VDC
• Electrical frequency in Hz
• Single phase or three phase electric power

NEMA standard electrical equipment enclosure type: For information on NEMA enclosures, see the Standards link below.

Refrigerant type: For more information about refrigerant types, follow this link.

Control systems: Temperature and humidity controls and thermostats range from simple switches and settings to sophisticated programmable units. Additional information about thermostats and thermal switches is available here.

Some applications require additional features:

• Condensate evaporators minimize or eliminate need for draining.
• Explosion-proof devices prevent explosions within the device.
• Intrinsically safe (IS) products minimize effects that cause ignition in the environment.
• Thermostatic control uses feedback from the cooling operation to maintain desired environmental conditions.
• Weather resistant units can safely be placed outdoors.

Different physical facilities make unique demands on temperature and humidity control systems.

• Data center air conditioners handle heat discharged by electronic equipment. These environments can require powerful air filtering and spot cooling.
• Process and plant Cooling systems cool spaces or chambers where heat transfer is required. Cleanrooms require careful attention to air filtration as well as airflow within the chamber.
• Hospitals and medical facilities, like cleanrooms, have requirements that can include microfiltration and airflow regulation.
• Telecommunications equipment centers can require both indoor equipment and outdoor, sheltered equipment. 

Standards

SAE AIR806 - Air Conditioning of Aircraft Cargo

ASHRAE 90577 - Thermal Guidelines for Data Processing Environments

Image credit:

Pfannenberg Inc.