The NEWS - February 18, 2008 - (Page 60)

service & maintenance Matches AC System Output to Changing Loads, Maintains Comfortable Humidity Levels Most AC systems lack subtlety: they either run at full capacity or they’re off. Under low load conditions, most systems quickly cool the air and then shut down, allowing humidity to build. The APR Control lets AC systems operate at less than full capacity so they continue to dehumidify without overcooling. ■ ■ ■ For retrofits or new DX systems to 100 tons Ideal for makeup air and VAV systems Fast, simple installation TEL : 800 727 6447 FAX: 781 933 3306 sales @ rawal.com RAWAL DEVICES, INC www.rawal.com A small air conditioner coil with one UV bulb mounted in the center. Only one half of this coil has UV protection as the outer sections have no UV bulbs. eProduct #30 at achrnews.com al021808.indd 1 1/9/08 shining directly on at a distance of usually less than 6 to 8 inches. Some UVC light companies state 10:17:16their UV systems can kill 99.9 AM Standard Reliability. The SST water-cooled condenser. The dependable choice for both OEMs and aftermarket replacements for over 40 years. • Serviceable design for easy cleaning. • Generous pumpdown capacities. • Heavy wall copper tubes for durability. • Epoxy coated tubesheets prevent pitting. • state of the art heat transfer service and tube geometry. Standard Refrigeration Company 2050 N. Ruby St. • Melrose Park, IL 60160 Phone (708) 345-5400 • Fax (708) 345-3513 www.stanref.com StandardRef011507.indd 1 eProduct #81 at achrnews.com percent of MRSA bacteria on a single pass and then reference an EPA study. This is very misleading as the test was conducted on a test unit of five UV high-energy lamps, each 50 inches long in a reflective tunnel, which burns 1,100 watts of electricity. This is the equivalent of running a hair dryer in your air conditioner 24 hours a day. This obviously generates a lot of heat in addition to burning a lot of electricity, and the units cost thousands of dollars. This system is not something the homeowner would install. This is an industrial UV system; very expensive, heavy-duty systems for food processing or medical applications. The EPA study specifically distinguishes this from UV devices that are designed to treat specific surfaces within the HVAC system; in particular, the cooling coils and the condensate drain pan to prevent biological growth on those surfaces. A standard 12- to 24-inch HVAC UV light system installed in an air conditioner coil will destroy mold and bacteria growth on the coil surface that the UV light shines on. What sections of the coil the light does not hit will grow mold and bacteria. The UVC lights used on an air conditioner coil will provide little, if any, airborne microbial kill as the UV energy and dwell or exposure time is not nearly enough to kill fast-moving airborne microbials. UV technology is very simple. Take a known quantity of UV light and expose a surface or substance to the light for a specified period of time, and a percentage of the microbials are killed. The product of the UV light intensity, multiplied by the time at that intensity, is termed “CT value.” Tables of CT values have been published, and are well-known. To properly determine what values to use, look in one of those tables and pick a microbe, then read the corresponding CT value, and design the system around that CT value. (Note of caution: Unprotected UVC lamps were used for this article. In practice, protected lamps should always be used as UV lamps contain mercury, a hazardous heavy metal known to cause health problems. A broken lamp in an HVAC system could permanently contaminate the system.) Typical HVAC home systems operate around 2,000 cfm for a 2,000-square-foot home. For example, 2,000 cfm will have an exit velocity of 500 feet per minute, or 8.33 feet per second. From this value, the proper residence time can be evaluated for specific CT values. Typical molds found in household are in the Aspergillius family. Aspergillius has CT values for a 90 percent kill ranging from 44,000 to 132,000 uWsec/cm2. Bacillus subtilis spores, a common bacteria, has a CT value of 11,600 uW-sec/cm. For example, we will use the Bacillus number, because as we will see, that relatively low number will mean a relatively high residence time. CT values higher than Bacillus will require an even longer residence time. The lamps can be placed at the outlet or inlet of the coils; however, at this flow rate, you will only have a residence time of 0.24 seconds. That is only 1.7 percent of the required 14.5 seconds for 90 percent kill. That is not even close to the required CT value to kill Bacillus. In fact, this value is so small, the UV will have next to no effect on any airborne pathogens. OZONE Concern about ozone and HVAC air cleaning devices is often exaggerated. All UV light lamps emit some ozone. UVC germicidal lamps emit very low levels, way below federal safety limits. Many everyday items emit ozone, such as: ■ 12/7/06 4:02:56 PM 60 AIR CONDITIONING, HEATING & REFRIGERATION NEWS February 18, 2008 http://www.rawal.com http://www.rawal.com http://WWW.ACHRNEWS.COM http://www.stanref.com http://www.stanref.com http://WWW.ACHRNEWS.COM

Table of Contents Feed for the Digital Edition of The NEWS - February 18, 2008

The NEWS - February 18, 2008 Turnout Contents Newsline FYI Unitary Oil-Fired Products Furnaces Hydronics Ductless Rooftops Drives & Motors Controls Transmitters, Sensors Zoning Valves Refrigerants Condensers & Coils Heat Exchangers Cooling Towers Chillers Duct Products Humidification IAQ Monitors, Instruments Trucks Tools Software Installation, Maintenance of HVAC Coils Munters MCS Dries Up Water Concerns at Hospital Michigan Home Show Brings out Contractors Investigating Furnace Failures Mold/Bacteria Protection of A/C Coil Learning Center Classifieds Advertisers Opinions

The NEWS - February 18, 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.