Do All DOAS Configurations Provide the Same Benefits?

Abstract

There are many potential benefits in applying dedicated outdoor air systems (DOAS) such as it is easier to ensure proper ventilation; decoupling latent and sensible loads control; providing energy use and demand reduction and better indoor environmental quality (IEQ). To realize the ventilation benefit of DOAS the OA must be supplied to each occupied space, or either directly, or in conjunction with, local units. There is more than one way to condition the air from a DOAS unit. While the dehumidified OA should be delivered cold whenever possible, as the space sensible cooling load decreases, this cold air may provide more sensible cooling than the space requires, resulting in overcooling. When the potential for overcooling exists, design engineers typically may consider implementing CA temperature reset to reduce the cooling capacity. When the conditioned OA is delivered at a cold temperature, rather than reheated to neutral, this configuration offers the opportunity to reduce the local equipment size and hence also its capital and possibly operational energy costs. When the OA is delivered at a cold temperature, rather than reheated to neutral, this configuration may also permit the downsizing of the local units.