Founded in 1875, this well-known university in the western United States has a main campus on 560 acres of land with 311 buildings that serve 27,000 full-time students.
A Viledon® filter representative approached the university stating they could supply a synthetic media final filter that would last two years and not require a prefilter. A university representative called in Camfil to validate the information and to request a side-by-side test with the proposed product. The Camfil distributor and regional sales manager conducted a lifetime efficiency presentation (fine fibre micro-glass vs. coarse fibre electrostatically charged synthetic media) that compared Camfil’s product to Viledon. Camfil also demo’d its filtration life cycle costing software for energy savings and total cost of ownership considerations. From there, the university asked Camfil to set up an in-situ test.
Forty filters from each manufacturer were installed in the east and west air handling units (AHUs) in their business building. Forty 24x24x12" Camfil Durafil® V-bank 65% fine fibre final filters were installed in one AHU. In a second AHU of equal airﬂow and outside air intake location, 40 Viledon T-60 24x24x26" 8-pocket bag filters were installed. Airﬂow per AHU was run at 56,000 cfm. While the units normally operate at 40-70% fresh air intake for particle counting stability, the dampers were set to 100% recirculation during the days of efficiency testing.
The test was run for 52 weeks with intermittent data collection and verification. Camfil in-situ test equipment was used, and all tests were observed by the university staff and competitor’s representatives. The tests were conducted in accordance with Eurovent 4/10 1996 (In-Situ Determination of Fractional Efficiency of General Ventilation Filters). The tests were done with no prefilters in place, at the request of Viledon.
“Specially configured media proves itself far superior to the electrostatically charged synthetic media in efficiency and energy savings.
The superior performance of Camfil’s specially configured fine fibre media proved itself far superior to the electrostatic charged synthetic bag filter media both in efficiency and energy savings. After a 52-week analysis, the Camfil product proved to save the customer $14 per filter per year versus the Viledon alternative while delivering three times the air quality level.
After 52 weeks, the Camfil final filter was at 33% efficiency on 0.3 micron particles (delivering almost two and a half times the level of air quality) versus the Viledon efficiency of 15%. The Camfil filters maintained a higher efficiency than Viledon for every particle size range tested. The Camfil filters were operating at less than 1 inch in static pressure drop, and at 40% lower resistance than Viledon, leading to substantial energy savings.
A life cycle costing (LCC) analysis proved that the Camfil Durafil filter operated at a 24% lower energy cost per year than the Viledon T-60. The Camfil product would save the customer $14 per filter per year versus the Viledon alternative.
The Viledon T-60, like the majority of synthetic media filters, relies on an electrostatic charge to maintain efficiency. Viledon and other manufacturers of synthetic media filters propose that their filters will maintain efficiency when the charge dissipates due to an increase in mechanical efficiency resulting from a build-up of dust. While this holds true over the several hours of loading in an ASHRAE test, it doesn’t hold true in real-life applications where loading takes place over longer periods of time.
In this test, the Viledon filter (and synthetic media) was given every opportunity to show sustained efficiency over time. The 85% efficiency filters formerly used in another building were replaced with 65% filters for this test. This should have made the efficiency results for the synthetic filters look better because 65%-synthetic filters rely less on the electrostatic charge than higher efficiency synthetics (the efficiency of 85% synthetics would have fallen farther).
At the request of the Viledon representative, the prefilters were removed for the duration of the test. This might have caused the synthetics to load up with dust faster and achieve the bridge to mechanical efficiency sooner. But despite this potential advantage, the efficiency of the Viledon filter was well below industry standards for 65% filters. The Viledon filter did not recover over the one year test period.
The Camfil Durafil 65, on the other hand, maintained an efficiency well above the standard for the entire test period. Glass micro-fibre media does not require a charge to maintain a mechanical efficiency at any efficiency rating from 65% to 95%. The Durafil filter also has a lower overall static pressure loss and a higher dust-holding capacity.