AMCA In Motion - Fall 2016 - 23

tested and certified to reject sand. ANSI/AMCA Standard 500-L defines these sand-rejection louvers (simply called "sand louvers") as comprised of multiple vertical or horizontal blades that, when mounted in an opening, permit the flow of air while minimizing the ingress of airborne sand particles. In plain terms, these louvers multitask; while serving the purpose of letting fresh air in, they also serve the purpose of keeping sand out. AIRBORNE SAND PROBLEMS HVAC equipment needs prescribed amounts of outdoor air to function properly, and that air is typically provided through weatherproof ventilation louvers installed on building facades. When an airstream loaded with sand particles makes its way through the louvers, it deposits the sand onto the floors and in the air near machinery, which then clogs the air filters of HVAC equipment in mechanical rooms. These sand-related problems have created real costs for HVAC service companies. MERV-rated air filters intercept low-range particle sizes of 0.3 microns to 10 microns and up to 62.5 microns to 80 microns on the high range. As the filter becomes clogged, energy use increases, and the resistance to airflow takes a toll on the air-handling unit compensating for the blockage of airflow. Building owners, then, will deal with more than the need to frequently replace air filters; they will also see sand intrusion drive up utility bills and take a toll on Figure 2. Sand louver with inclined plate, usually called a drain sill. Image courtesy of Ruskin Titus Gulf. their equipment. More severe costs begin to accumulate as well. The reduced airflow from clogged air filters can cause a chain reaction of HVAC industry has relied on filters inside HVAC and other costly problems. Insufficient airflow through a heating and mechanical equipment, rated in accordance with two different cooling system can cause overheating of the ASHRAE test standards: ASHRAE Standard air-handling unit, heat exchanger and genera52.11 which rates filters according to dust spot tor, which in turn can cause a premature efficiency, and ASHRAE Standard 52.2,2 shutoff. If that shutoff happens too often, the which rates filters for minimum efficiency electronic limit switch safeguard can fail, and reporting value. ASHRAE 52.1 has been then the air-handling unit will not function withdrawn, so ASHRAE 52.2 is the active until it is serviced. Parts and labor for this can ASHRAE filter-rating standard. easily cost in the $200 range. Additionally, wind-driven particles travelCleanup costs will also begin to mount for ling at high speeds would be intercepted by a building in a sand-afflicted zone. Sand needs a fan unit's filters, rated in accordance with to be removed from floors, ducts, air-handling ASHRAE 52.2. Conventional louvers not units, rooftop air conditioners and other airtested for sand infiltration allow wind-driven system components. Service calls are frequent, sand and dust particles traveling at high speed creating a drain on time and budget. to be intercepted by MERV filters, and this These are all preventable expenses because sand penetration leads to rapid clogging and Figure 3. Current ANSI/AMCA there exists a cost-effective means of trapping choking of the ventilation equipment. Only Standard 500-L cover. Image sand and depositing it on the ground along courtesy of AMCA International. frequently-scheduled or alarm-driven mainthe building facade. This solution is the sand tenance measures can prevent this. The louver. Basically, sand lovers are prefilters. They solve the problem is compounded since, over the last decade, HVAC problem of excessive sand intrusion before the building equipment has become more air-quality sensitive. Some facilienvelope is even breached. ties report as much as an 80 percent increase in maintenance cost due to dust/sand infiltration, and that substantial increase A HISTORY OF THE PREFILTER SOLUTION is not an anomaly-it is a trend. The need for a prefilter soluThe use of sand louvers as prefilters is relatively new, only tion appears to only be increasing as HVAC equipment beginning to come into use in the 1980s. Historically, the technology advances. W W W. A M C A . O R G AMCA inmotion Summer 2016 23 http://WWW.AMCA.ORG

Table of Contents for the Digital Edition of AMCA In Motion - Fall 2016