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UV Systems Can Help Restore Optimal HVAC Operation
November 14, 2014 - Contact FacilitiesNet Editorial Staff »
Many facilities are using ultraviolet light to help improve indoor air quality and reduce energy costs in buildings. Here, author Loren Snyder discusses how UV technology in HVAC came to be used and one of the two common UV system types available to clear systems of microorganism: coil systems.
In most HVAC systems, the high humidity environment around the condenser coil and condensate pan is a prime environment for molds and other microbes. Many microbes will adhere to wet surfaces using a starchy or sugary substance they produce as their anchor. This build up of microbial growth is called biofilm, and can grow thick enough that it effectively chokes airflow through the coil. The biofilm build-up on coils can be as much as several millimeters thick, compromising capacity in air-handling systems.
"[Biofilm can] increase air flow velocity and moisture carry-over," says Tim Leach, healthcare solutions director at Steril-Aire. "Water is no longer efficiently running into the condensate pan, and biofilm is insulating, so it reduces heat exchange. Because it can be several millimeters thick, it can account for 10 to 40 percent efficiency loss in some systems."
Back in the 1980s, it was hypothesized that that microbes can also blow off the coil and enter the airstream, either landing and consequently colonizing portions of downstream ducts, or entering occupied space along with the conditioned air. Early efforts to reduce this problem focused on arming technicians or custodial staff with chemicals that were applied to the coil and condensate pan to eradicate microorganism growth. Reports of success were varied, but obviously it often introduced cleaning agents to the air entering occupied spaces — up to several times during a 12-month span, according to Forrest Fencl, president of UV Resources — and the practice also exposed the workers cleaning HVAC systems to both the chemicals and high concentrations of microorganisms.
But several in the industry had paid attention to the use of ultraviolet light in equipment sterilization and water purification, and reasoned the same technology could be used on condenser coils. Placing a UV light source close to the coil can restore coil capacity by killing microbial growth and the consequent shrinking of the biofilm layer on the coil.
Read the full article on UVC systems here.