Filter for a Pentz Air Cleaner
I want to make a Pentz Air Cleaner so I can keep the air clean while I use non-electric tools.  If you are unfamiliar, this is an 8" centrifugal fan on top of a large canister filter.  My plan is to use these supplies:

Filter:  Clark NF20011 nanofiber, MERV 15, 260 sqft of filter
Pre-Filter:  30 PPI Speaker Foam that I wrap around the filter
Fan:  FanTech FG8

My shop is small, so this will be permanently mounted on a shelf near the floor.

This is not exactly what Pentz recommended, but the fan he recommended seems to be low quality and the Wynn filters are $120 more with a longer lead time.

Does anybody have any feedback or suggestions on this plan?

Only that I think your plan is good. I do have some experience with Clark filters. I replaced the Oneida OEM cyclone filter with one. It was a lot more robust in construction, just as tight (Merv 15, IIRC) and a he!! of a lot cheaper. More media as well. They are USA made and top notch. I replaced my Oneida with a CV which has the Wynn filters, they are also very good...but probably not so good that's they are worth a premium.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
Thank you for alerting me to the less expensive Clark filters.  I have been happy with the WynnEnv filters I got for my Pentz design cyclone years ago, but I'm thinking of making another air filter and will probably follow your sourcing of filter and fan, as they look good to me.
This filter market is strange.  There are a lot of websites that sell industrial replacement filters.  They all seem to be different companies that operate in a similar manner.  They want large industrial orders, not individual woodworkers, asking lots of pesky questions.  I found a comment to that effect on another forum from the owner of  I am completely sympathetic.  These companies often point us back to Wynn Environmental, who has built a niche of providing filters to woodworkers.

The other thing I found interesting is that the Axiom Stratus, which is basically a commercialized version of the Pentz design, sells a MERV 15 replacement filter AND prefilter sleeve for $99.  The filter for the Stratus has no other specs, but the price is certainly more attractive than the $223 the Wynn charges.

So I wrote Wynn asking about less expensive filters I could use to build an air cleaner and he said there are no other MERV 15 options.  Given there are a zillion different filter configurations, that seemed very unlikely, so I started doing my own searching.

The specs of the Wynn 9L300NANOEXT filter are 34" tall, 12.75" outside diameter, 8.4" inside diameter, flange of 14.25" x 16", open on both ends, 300 sqft of nanofilber media, and MERV 15.

Using the dimension searching on Filter Junkie, I found a FARR 211736001 which is almost the same specs except the non-flange end is closed, not open like the Wynn model.  The open end is where Pentz mounts the fan. I was not able to find a filter with a flange that is open on both ends except for the Wynn 9L300NANOEXT.  I suspect that the open filter end, being willing to sell in small quantities, plus being willing to answer pesky questions is how Wynn has become the go-to for woodworkers.

The more I thought about it, maybe the flange adds some stability, but I don't think it was designed for that.  It seems like I could improvise something else to provide stability if necessary.  I broadened the search to include all round filters that are open both ends and have 12.75" outside diameter and there are lot of options.  Many have identical specs, but different OEM part numbers.  In the Pentz design, one end rests on the ground, so it is treated as closed, but I think having both ends open will make it easier to clean.

I used the Filter Junkie search to narrow down the products.  Then I googled for the filter numbers to understand the OEM specs more.  It's curious to me that Filter Junkie has the same picture for lots and lots of filters, so I'm not sure if what is pictured there is actually what you get.

The one spec I have not been able to find is whether the air is expected to flow from outside to inside or inside to outside.  I have been assuming that nearly all of the filters are outside to inside, which is what you want for an air cleaner, but not a cyclone.  That's another part of Wynn's niche.

So if you are looking for a filter, I encourage you to do some of your own searching.

Maybe somebody who actually knows about filters will post something here to decipher this strange world.

I don't meet the criteria of "someone who knows about filters", but I suggest you look at this one at Penn State Industries. Just a short background piece on them. While they mostly cater to turners with pen kits and other turning accessories, at one time they had a fairly extensive line of (very good) dust collectors. For the cyclones they sold the filters I linked. I bought one to put on the Oneida I mentioned earlier, and it is made by Clark Industries. Quite some years ago someone told me Clark would not sell to individuals but it wasn't something I followed up on in any way. Regardless, maybe the one I linked will help...or not. But it does represent a very good buy for a canister filter.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
(03-05-2023, 07:03 AM)fredhargis Wrote: I don't meet the criteria of "someone who knows about filters", but I suggest you look at this one at Penn State Industries.

Thanks Fred.  From the specs on that site plus some research, it looks like that Penn State filter has the same dimension as a Clark 1279137 with nanofiber media and reverse flow.  That filter has good specs, but the flow direction is backward for my air cleaner.

I had trouble figuring out the air flow direction, so I'll share what I learned.  With woodworking cyclones, we send the air through the cyclone and then out through the filter.  So the dirty air is on the inside of the canister.  However, these filters are almost all designed for huge industrial dust collectors that blow dirty air against the outside of the canister and then suck clean air out through the inside.  This video shows an illustration of how it works:  In this configuration, they can clean off the filters by sending bursts of air through the inside of the filter, which knocks the dust off the outside, where it can fall down for collection.

So if you are buying a filter for the exhaust of a cyclone, then you want "reverse flow" where the dirty air is blown inside the filter and the clean air is on the outside.  One of the advantages of Wynn is that they take care of this detail and primarily offer "reverse flow" filters for woodworkers.

If you are building an air cleaner like I am, then you want "standard flow," there the dirty air is outside the filter and clean gets sucked through the filter.  Wynn's 9L300NANOEXT is configured like this.

I ordered my filter from  You can order standard flow through their website.  If you want reverse flow, then you can call and request a "reverse flow" filter and they will orient the media the other direction.  For liability reasons, they can't recommend a filter for DIY woodworkers, but they appear happy to sell them if you have the part you want to order.

You may be splitting hairs, or not. I know a lot of guys are using a Donaldson truck filter for their DCs, and that air flow would be the reverse of the filter design. There's be no mention of a problem, and all seem to be happy with the performance. That said, I do realize media has a direction for the air flow, but I suspect it's more important in heavier duty (industrial/commercial) applications than the typical ww'ing hobbyist would have. Regardless, I'll be interested in hearing how you cleaner works.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.

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