Case Studies of Commissioning HVAC Systems

Abstract

This paper discusses problems found during third party commissioning of projects where humidity control was an indicator of significant problems. Project 1 was an 8000 square foot library. Problems found included air conditioning (A/C) and heating systems both running during the summer, A/C systems that ran most of the unoccupied period, and relative humidity that was over 90% every night. Project 2 was a 1200 square foot meeting room. The outdoor air (OA) preconditioning system was found to operate in hot gas bypass mode with little humidity control capability. Project 3 was the heating, ventilating, and air conditioning (HVAC) system on a 400 square foot library conference room with electric reheat for humidity control on a three-ton split system. The design was for a humidistat to call for cooling on high humidity. Reheat was energized as the space temperature dropped below the heating set point. The system functions with a wide space temperature swing as the control system oscillated through the heating/cooling deadband.