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Low Temperature Air Systems

General

Low temperature primary air systems provide 42¡F to 48¡F supply air for comfort cooling. The principal advantages of this air delivery option over conventional systems include lower first cost, lower electrical demand and reduced operating costs.

The smaller fans and ductwork diameters required for low temperature air systems not only reduce equipment costs, but also offer the potential for architectural savings, since less floor-to-floor height is needed. And because the fans and pumps used require less horsepower, the system consumes less energy than many traditional types of air delivery.

Low temperature supply air also improves comfort levels by reducing the relative humidity in the occupied space. This reduction in humidity often results in a perceived improvement in indoor air quality. In addition, occupants tend to desire warmer space temperatures which can lead to additional energy savings. Typical room conditions for a low temperature primary air system are 78¡F with a relative humidity of 35 to 45 percent.

Proper care must be taken to ensure that condensate does not develop on the ductwork or terminal units. Selection of air diffusers is of particular importance to ensure adequate distribution at lower airflow volumes. And, particular care must be taken to assure required air changes for adequate ventilation (i.e., outside air at modulated conditions), as well as for smoke pressurization strategies.

Advantages

  • The principal advantages of this air delivery option over conventional systems include lower first cost, lower electrical demand and reduced operating costs.
  • The smaller fans and ductwork diameters required for low temperature air systems not only reduce equipment costs, but also offer the potential for architectural savings, since less floor-to-floor height is needed. And because the fans and pumps used require less horsepower, the system consumes less energy than many traditional types of air delivery.
  • Low temperature supply air also improves comfort levels by reducing the relative humidity in the occupied space.

Disadvantages

  • Because of delivery of low supply air, the unit efficiencies are generally lower.
  • If the ducts are not well insulated, a condensate dripping problem may occur.