Exploring Maximum Humidity Control and Energy Conservation Opportunities with Single Duct Single Zone Air-Handling Units

摘要

Humidity control for single-duct single-zone (SDSZ) constant volume air handling units is known to be a challenge. The operation of these systems is governed by space temperature only. Under mild weather conditions, discharge air temperature can get much higher than the space dew point and the dehumidification capability of the system is diminished. Buildings served by this type of air handler often experience exceptionally high humidity levels under humid weather conditions. Many potential solutions and improvements exist. However, these solutions require system modifications or upgrades and therefore are less attractive to some facility owners.A Critical Humidity Control Program (CHCP) was developed to change the normal control sequence of the air-handling units during high humidity periods to help improve the moisture removal capability of the system. The program was not designed to solve the problem completely, but the overall humidity levels can be lowered and controlled within a reasonably low range (58% - 65%) for a significant part of the high humidity seasons. This approach is relatively easy to implement and does not require any hardware changes.This paper also summarizes various potential solutions to improve humidity control for SDSZ units. The advantages and disadvantages for each solution are compared.