Reply by HorizontalMike

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Posted on Another Dust Collection Question

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7770 posts in 3084 days

#1 posted 09-26-2012 01:13 PM

I have now seen the comment of something to the effect of “A poor DC filter is worse than none IMO” a number of times now. Please consider the following from a “good” filter company. Even a “good” filter company(Wynn in this case), fully admits that filters actually NEED a break-in time to develop better filtering. This is because all filters do accumulate/cake with use, and it is advantageous that this process occurs. What this means is that even a 5.0micron filter will filter better than 5.0microns after sufficient break-in. In other words, do not under rate that stock filter bag on your cheap HF DC unit, because it gets better and better at filtering over time.

And BTW, I use a Thien separator on mine as well.

”...We get occasional calls about our posted 99.99% efficiency, as it compares to the ASHRAE 52.2 test standard.
The chart below shows the Particle Size Efficiency of a filter made from our 80/20 blend, based on the ASHRAE 52.2 test standard. The numbers just below the chart (beginning with 0.35) are the particle size “geometric mean”, in microns.
As you can see, these filters test very well, but the results do not indicate the 99.99% at 0.5 micron rating that we have given to our 80/20 blend. This is because the ASHRAE 52.2 test standard is not designed for round pleated cartridge filters. More importantly, it is not designed for cleanable filters. It was actually designed to test flat disposable HVAC filters, so the resulting data needs to be taken with a grain of salt. The ASHRAE 52.2 test does not give a true indication of what a user should expect to see from their dust collection filter…it can only tell you what the filter will do when it is brand new.
Background info and further explanation:

-ASHRAE 52.2 requires a minimum face velocity of 118 fpm. This equates to over 1100 cfm on our Farr style filters! We never push these filters past about 750 cfm, and normally run them at about 500 cfm, so the 52.2 test pushes them way beyond their intended flow rating. ASHRAE 52.2 gives all cartridge filters (not just ours) an unfairly low indication of the true as-installed efficiency. ...”
More info here

-- HorizontalMike -- "Woodpeckers understand..."

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