An economizer uses outside air to reduce the refrigeration requirement. A logic circuit maintains a fixed minimum of ventilation outside air. The air side economizer…

Resistance through outdoor intakes varies widely, depending on construction. Frequently, architectural considerations dictate the type and style of louver. The designer should ensure that the…

The negative pressure in the outdoor air intake plenum is a function of the resistance or static pressure loss through the outside air louvers, damper,…

Relief openings in large buildings should be constructed similarly to outdoor air intakes, but they may require motorized or selfacting backdraft dampers to prevent high…

Opposed blade dampers for the outdoor, return, and relief airstreams provides the highest degree of control. The section on Mixing Plenum covers the conditions that…

In many situations, a relief (or exhaust) air fan may be used instead of a return fan. A relief air fan relieves ventilation air introduced…

A return air fan is optional on small systems but is essential for the proper operation of air economizer systems for free cooling from outside…

To determine the system’s air-handling requirement, the designer must consider the function and physical characteristics of the space to be conditioned and the air volume…

The methods used to humidify air include • Direct spray of recirculated water into the airstream (air washer) reduces the dry-bulb temperature while maintaining an…

The basic methods used for cooling include • Direct expansion, which takes advantage of the latent heat of the fluid, as shown in the psychrometric…