@TheTiddles is quite right to say that (except on the large industrial scale) commercial systems steer clear of cyclones: as I see it now that is not a rejection of Pentzism, it is an acceptance of it: he is I think saying don't look at quoted single figures for cfm, work out what pressure your duct system needs to achieve your acceptable cfm and size your fan (and/or scale your ducting) accordingly; if you want a cyclone then have one---but it adds to your duct resistance; if you really want one then the Pentz design maximises extraction without adding too much resistance; but it still adds enough resistance that you need to upgrade your fan.
Commercial sites venting outside seem nowadays to be required to use some form of fine filtration for hardwood or MDF (softwood seems to be ok to be vented after coarse filtration or cyclone alone), but the fine filtration we are talking about is not HEPA standard, and having drunk the Pentz koolaid I don't want that back inside my workshop. HEPA filters are available, but need to be maintained: clogging reduces the cfm but maintains or indeed enhances the filtraton; punctures maintain or indeed enhance the cfm but compromise the filtration.
Non-commercial sites (and probably quite a few one-man bands) probably don't really know what they're getting because they are neither doing rigorous design, nor checking pressures, flow rates and particle counts on the actual system. There are quite a few people (pre-Pentz, I'm one of them) who have been delighted to discover that fitting a cyclone reduces the dust on their filters. Well yes .... but it's also reducing the flow through their system. Getting 1000cfm through an affordable system is no cinch.
That's how I now see things ... but it's a tricky area and my thoughts are still developing.
Commercial sites venting outside seem nowadays to be required to use some form of fine filtration for hardwood or MDF (softwood seems to be ok to be vented after coarse filtration or cyclone alone), but the fine filtration we are talking about is not HEPA standard, and having drunk the Pentz koolaid I don't want that back inside my workshop. HEPA filters are available, but need to be maintained: clogging reduces the cfm but maintains or indeed enhances the filtraton; punctures maintain or indeed enhance the cfm but compromise the filtration.
Non-commercial sites (and probably quite a few one-man bands) probably don't really know what they're getting because they are neither doing rigorous design, nor checking pressures, flow rates and particle counts on the actual system. There are quite a few people (pre-Pentz, I'm one of them) who have been delighted to discover that fitting a cyclone reduces the dust on their filters. Well yes .... but it's also reducing the flow through their system. Getting 1000cfm through an affordable system is no cinch.
That's how I now see things ... but it's a tricky area and my thoughts are still developing.
