Ventilation Air Preconditioning Systems

Abstract

Increased outside ventilation air requirements demand special attention to how that air will be conditioned. In winter, the incoming air may need preheating; in summer. the mixed air may be too humid for effective dehumidification. Part-load conditions pose greater challenges: systems that cycle on and off allow unconditioned air into the building during compressor off-cycles. The Electric Power Research Institute has teamed with manufacturers to develop dual path HVAC systems, with one path dedicated to preconditioning the outside air. This paper discusses two such systems for cooling and dehumidification applications: one with a separate preconditioning unit and one with separate ventilation and return air paths in a single unit. Both deep-cool and deep-dry the incoming air before mixing it with the return air, thereby eliminating the latent load on the primary cooling coil. As unitary packages, they are easy to install in new and retrofit applications. Also, their excellent energy efficiency cuts electric energy consumption, providing significant operating savings.