Case Study: Enhancing Air Quality and Efficiency with Ultraviolet Light

By Consulting Specifying Engineer Staff July 5, 2006

At the headquarters of the American Society for the Prevention of Cruelty to Animals (ASPCA) in New York City, indoor air quality and infection control are always of concern. “We need to keep the air as clean as possible to protect the health of staff, volunteers, and of course, the animals,” states Vincent Grujic, ASPCA director of facilities. “In addition, we wanted a way to get more life and efficiency from our air handlers.”

The ASPCA was already using ultraviolet light technology to disinfect bottled water in a holding tank, so Grujic was familiar with the germicidal properties of UVC energy. He was not aware, however, of the availability of a new generation of UVC devices that are specially designed for use in air handling systems. In 2004, Scott Sherwood, president of Eco-Care Corp., New York, a company specializing in pollution control and energy conservation, suggested that the devices could provide the ASPCA with multiple benefits of IAQ and infection control, HVAC maintenance savings, and energy efficiency.

UVC energy is the most germicidal wavelength in the ultraviolet spectrum. Properly installed in an air handling system, UVC lamps emit enough of this energy to penetrate even the tiniest microbe to destroy its DNA and RNA, killing or deactivating it.In this manner, UVC effectively stops both surface organisms that grow inside HVAC systems and airborne microbes that circulate through these systems to the occupied space.

UVC is said to work against viruses (including colds, bird flu and other strains of influenza), bacteria (including pneumonia and TB), and mold and mold spores, which account for much of the illness and discomfort in buildings today and many of the maintenance and operational headaches. Since the five-story ASPCA building includes extensive animal housing and the BerghMemorialAnimalHospital, a full-service small-animal medical facility, any technology that helps prevents the spread of infection is of paramount importance.

“Eco-Care had already equipped the ASPCA air handlers with 95 percent ASHRAE efficiency (MERV 14) bag filters for air quality enhancement, and EER units for energy conservation,” notes Sherwood. “We believed, however, that UVC lights could add another dimension of IAQ control and energy performance.”

Since the facility was about to embark on a major renovation, the ASPCA agreed to have Eco-Care install UVC lights in three AHUs serving the building on a phased basis, including two 15-year-old existing units (one 90-ton and one 40-ton unit) as well as a new 50-ton system serving the renovation floor. The AHUs typically run “24/7” with air exchanges every four hours, and 100 percent outdoor air for disease control.

The result was that after Eco-Care installed lights in the existing AHUs, Grujic quickly noticed a big improvement in system efficiency. He reports: “During the summer of 2005, one of our hottest summers on record, we were actually getting complaints that the building was too cold. After looking into the reasons, we found that the temperature at the coil of our 90-ton AHU was as low as 47

Grujic adds: “The previous year, we noticed some improvement after installing the EER units, but we certainly weren’t getting these low temperatures. The UVC lights made a big difference. Our coils used to be clogged up, and heat transfer was compromised as a result. UVC keeps the coils so clean that it basically rejuvenates our systems and allows them to run as efficiently as when they were new.” With energy costs now at about 22 cents per kW, Grujic expects that the energy savings over time will be significant.

There is another benefit to having the A/C coils continuously cleaned by UVC: the reduction or elimination of coil cleaning as a scheduled maintenance task. “Workers are no longer exposed to cleaning chemicals, and we also eliminate the problem of chemical residue recirculating back through the building as air blows through the coil after a cleaning,” says Grujic.

UVC has also solved the problem of contamination in drain pan areas, Grujic reports. “We used to have a lot of rust and organic material going down the drain, and now the problem has virtually disappeared,” he says. Worker exposure to chemicals in these areas has again been eliminated.

“I don’t like to send our crews into the AHUs too often, because bacteria and mold can naturally collect there. UVC lights reduce this problem dramatically,” Grujic states. The lights themselves require no maintenance except for an annual changeout. The doors to the AHUs are equipped with a double-switch backup system so that no one can enter the unit with the lights on. This safety system prevents direct exposure to the UVC light rays.

The ASPCA recently installed a new, replacement AHU as part of its extensive renovation. They ran this AHU initially without UVC lights.mulate. Culture plates confirmed the existence of multiple cultures of microorganisms. By equipping the AHU with UVC lights, the facility expects the coil to become clean and free of microorganisms and debris, operating once again at peak heat transfer capability.

The remodeled facility will provide canine and feline boarders with expanded housing that Grujic and others describe as “condos” because of their spaciousness and their premium construction, which incorporates radiant heating, Corian walls, windows and numerous other amenities.

For more about UVC for HVAC systems from Steril-Aire, click here .