Filter sizing

[JimmyTheHand]

Hi,
I built a dust collector with a thien baffle a few years ago, using a 3 hp blower with a 160 mm hoses and pipes.

Until now, the blower blows the air outdoors. This has worked well, but cools the workshop down quite a lot in the winter.

I am moving this summer, and will have neighbors too close to just let it blow outdoors in my new workshop (because of the noise - it sounds like a jet engine). So, I'm looking at adding some filters to let the air back into the workshop.

My first thought was to make two rectangular drawers, one with a coarse filter, and one with a hepa filter. This feels like a great setup, as I can just pull out the drawers and clean them outdoors. However, I've started wondering if these filters will let enough air through. Maybe this would remove too much suction power from the dust collector.

Would a hepa cartridge filter be better? Like this one:
https://www.axminstertools.com/hepa-filter-for-t-2000ck-2hp-cyclone-505090

That one seems to be designed for a 2 hp blower. Maybe it would be too small for my 3 hp blower?

I'm attaching a drawing of the version with two filter drawers. It's a see-through version, so the walls around the output are not visible.

[retired2]

I don?t remember where I saw them, but I?ve seen descriptions for building noise reducing enclosures for a DC system.  They are small closet sized enclosures so they don?t take up a lot of space and if done right are pretty effective at reducing the noise.  They vent back into your shop which is what you want.  I?m not sure I could stand working in a shop with a 3 hp system without some serious noise suppression. 

The best filter to use is a cartridge style pleated filter like the one you are looking at. They have about twice the filter area of a bag style filter.  As far as size, call the manufacturer they should be able to quickly recommend one suitable for your system.

[JimmyTheHand]

Thanks. I actually have a noise suppressor now,  just to take the noise level down a bit at the output. It actually makes a big difference. I'm attaching a drawing of it.

I might be able to use the same idea in a larger scale, by building a small room around the whole dust collector, using sound dampening material on the inside walls, and then a large hepa filter on the bottom.

[retired2]

The design I remember had a few baffles to redirect the exhaust air several times before it hit a large filter at the bottom of the door.  The airways were large enough that it did not creat any back pressure on the blower.