What is Ultraviolet Light?
The light we can see is just a portion of the light spectrum. Ultraviolet light is also invisible but has a higher frequency than visible light. The frequency of UV light is between 90-400nm. The effective range for disinfection is UV-C (200-280 nm with peak germicidal effectiveness at 254nm). This is also referred to as UVGI light (which stands for ultraviolet germicidal irradiation). UV-C light from the sun is filtered out by the Earth’s atmosphere so microbes have no defense against it. Exposure to UV light has a devastating effect on microorganisms. The very short wavelength of UV-C light penetrates the membrane and nucleus of microorganisms and breaks apart the molecular bonds of DNA. This inhibits the organism’s ability to reproduce, effectively killing it.
Improved Indoor Air Quality
By keeping HVAC system components clean and mold free, UV light systems have been shown to greatly improve indoor air quality. A well-known study by the medical journal “Lancet” in 2003 showed that UV lights reduced microbial contamination within the HVAC system by greater than 99% and reduced occupant respiratory illnesses by more than 40%.
How Does UV Light Provide Energy Savings
The UV light system is typically placed downstream and facing HVAC coils and operated continuously. This placement helps to inhibit the growth of mold and bacteria on the coils that, if left unchecked, can accumulate and grow there, robbing the system of performance. By keeping the coils clean, the UV system will improve static pressure across the coil reducing the load on the blower and improving heat transfer which both contributes to significant energy savings. Studies have shown that a bio-film thickness of only .002″ on the coil surfaces can reduce the free area and increase air velocity up to 9%. By rejuvenating the coils and maintaining greater heat transfer, this can result in an impressive 30% increase in cooling capacity when compared to a system with a dirty coil.