Battling Moisture, University Finds Ultraviolet Solution

The Challenge

When your campus is home to 27,000 students, indoor air quality (IAQ) is of the utmost importance. The University of Arkansas has 100 buildings served by approximately 150 air handling units (AHUs). Rick Gragg, HVAC Coordinator with the university's Utility Operations Facility Operation department, has supervised a decade-long mission to improve IAQ. "Moisture is an ever-present threat in air handlers because the evaporator coil operates at a temperature less than the dew point," explains Gragg, a 35-year HVAC industry veteran. "As moisture is drawn out of the air to yield cooler temperatures to room occupants, the resulting condensation provides the perfect environment for mold and other harmful contaminants to flourish." In 2010, an algae-like growth had developed in the Harmon Parking Garage AHU's condensation tray — viscous enough to clog the drain tube. Efforts to unclog the drain and kill the algae with chlorine tabs were not only ineffective but unintentionally corroded the metal drain pans. The resulting overflow of water cascaded into an IT network closet below the AHU, ruining sensitive electronic equipment.

The Solution

Gragg worked with a contractor to install UV-C lamps in a variety of HVAC systems across campus over a multi-year period. The first trial was the Health, Physical Education and Recreation Building (HPER), where neither coil had been cleaned prior to adding UV-C — ensuring any system changes could be attributed directly to the UV additions. The RLM Xtreme fixtureless UV-C lamp system was selected for its flexible configurations, critical for the difficult-to-access coils in the parking garage and other campus AHUs. Over a three-month period of UV-C treatment, measurements at the HPER building revealed a coil pressure drop decrease from nearly 1.0 inches to less than 0.8 inches of static pressure — energy savings in addition to disinfection. Researchers have found that exposing a fouled cooling coil to UVGI resulted in a 10 percent decrease in pressure drop and a 14.55 percent increase in heat transfer coefficient at reference conditions.