Auto-SummaryThe user encountered issues with a 48" x 24" x 6" Koch Biomax filter from Zoro.com, which arrived damaged and failed under the blower's capacity, despite the user's calculations. The filter's actual capacity was found to be only 1100 cfm at 1" resistance, not sufficient for a 1/2 HP blower's 1162-1654 cfm range. The user then switched to a 48" x 24" x 6" filter from Earthstongue, which they believe has a higher capacity. They emphasize the importance of choosing a filter with a higher CFM capacity for laminar flow builds.
Ran into a snag with my flowhood build that I wanted to mention here for reference and maybe get some more advice.
I originally went with a 48" x 24" x 6" koch biomax filter from zoro.com. They had the best price for the filter. Well the filter arrived damaged, the wooden frame was cracked completely through on one side. Glued it back together thinking it looked fine enough, but after installing the filter in the plenum and turning on the 1/2 hp blower, a tear in the filter immediately appeared. (Pic included below)
When choosing that brand of filter, I was referencing the koch biomax chart El Chupacabra posted. Since it didn't actually have the 48" wide filter specs listed in the chart, it wasn't that useful but I noticed that it probably has the same 1"wg resistance as the other standard capacity filters in the chart. I also referenced the CFM capacities, but at the time didn't notice the chart is split by 6" deep and 11" deep filters. Neither of them are in the 48" wide size, so I just took the 24 x 24" filter capacity and doubled it, not realizing I was using the 11" deep capacity.
When I correctly double up the capacity for the 6" deep filter, I determined that the 48" wide filter's capacity is only 1100 cfm for the 1"wg standard capacity model. When choosing the filter, I paired it with the Dayton 1/2hp 1XJY1. Here's a PDF of the blower's CFM at different resistances. If you look at 1" for 1XJY1, depending on the speed it will deliver 1162 - 1654 cfm. If the 1100 capacity is correct and literal, then the 1/2hp Dayton at any speed would blow this filter. Adding .2" resistance for a pre-filter dials the fan down to an appropriate 846 - 1188 cfm. (still too strong on highest speed?)
I personally wired it to the 2nd lowest speed, which is 1393 cfm without the pre-filter. Knowing all this now, I can't say for sure whether the crack in the filter was caused by the cracked frame during the shipping, or if the filter just exceeded its capacity and immediately blew out.
According to the scaling on the smaller filters, the capacity of the 48" standard koch biomax should be just 1100 cfm but I can't find the figure directly printed anywhere online. The only two other sources for HEPA filters that weren't trying to ask me about its purpose were fungiperfecti and earthstongue. Both of these vendors advertise their 48" wide filters as 1250 cfm @ 1". I don't understand what this figure means, even after asking for clarification:
Quote: Fungiperfecti - The static pressure of most of our filters is 1", including the 48 x 24. That particular filter is rated for a minimum of 1200CFM at 1" static pressure. We recommend using the EAFB4 1/2HP blower, wired to the highest speed.
I don't understand how a filter could have a minumum cfm rating? Wouldn't the filter still create laminar flow at 100 fpm or a mere 800 cfm?
Quote: Me - On the product page, it says 1250cfm@1". What does this figure indicate? Is this a minimum or maximum cfm? What is the filter's cfm capacity? Which blower do you recommend pairing it with? Earthstongue - Those are the WG pressure numbers on the filters. That is how they are measured for cfm rating. They flow at least 1250cfm. At least 1/2 hp motor for this filter is enough. 3/4 hp tops.
"They flow at least 1250cfm (@ 1")" Also not sure what this is supposed to mean. Its capacity is at least 1250? Its minimum cfm is 1250?
At least they both seem to agree that a 1/2 HP blower on the highest speed is the sweet spot.
Basically, what I gathered after this epic failure is that the koch biomax brand of filters must be different from the brand that fungiperfecti and earthstongue use. If the koch biomax 48" wide standard capacity filter is really limited to 1100 cfm, then it would make a very poor choice for a flow hood because your window for laminar flow is just 800-1100 CFM. According to blower chart, you could hit that figure with the 1/2 HP blower on its lower speeds, with a pre-filter. But after seeing 1 filter blow, I didn't feel comfortable with that margin of error. A 0.5 resistance difference on the pre-filter could be the difference between blowing the filter or falling below laminar flow.
So I went back to the charts and koch biomax makes all their filters in a high-capacity model as well that doubles the CFM capacity; which would be perfect if it didn't also increase the resistance to a base 1.5". They also make filters twice as deep (6" and 12") which simply doubles the standard capacity while remaining at 1" resistance; but my flow hood was already constructed to 6" specifications.
I decided to go with the 48 x 24 x 6" filter from Earthstongue. They add protective grills to the front and back of the filter which I think makes a lot of sense after seeing how fragile they can be. I just hope that the CFM capacity is truly higher than the koch brand. They recommend 1/2 - 3/4 hp so it's gotta handle at least 1500 cfm you'd think? But again, I theoretically should only need 800 cfm for laminar flow soo I guess I'll start on the lowest speed.
TLDR: The 48" x 24" x 6" koch biomax 99.99% HEPA filter is probably not deep or dense enough for most laminar flow builds at its estimated capacity of 1100 cfm.
 
Edited by Icon (05/26/19 09:54 PM)
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