Homemade Shop Air Cleaner

[Jerry Bruette]

Anyone ever try a electrostatic filter in their homebrew shop air cleaner?

[Charles Wiggins]

Not mine: http://davidcox.org/wood/shop-built-...leaner-filter/

[Ian Scofield]

Built my own like Charles. I use some big box store filter for my 1st filter which is decent (Allergen Plus Pleated FPR 7) then I have a 5" thick LENNOX MERV16 filter to capture the super fines. Does an awesome job of cleaning out the air (from the amount of dust that cakes on the outside filter). I need to get a DYLOS to test the air...but at $300 I'm not in a rush to get it.

[Jerry Bruette]

Not mine: http://davidcox.org/wood/shop-built-...leaner-filter/

That middle filter is exactly the type I'm talking about. Right now I'm using two furnace filters on each side of my cleaner and was wondering about saving some bother and using a washable filter.

[Larry Edgerton]

I used to race off-road and so studied filtration. The best way to make filtration work is to drop the vacuum/pressure and slow the air down. The only way to do this given a specific cfm is to increase filter area.

I made a hanging filter that had the same type of fan, a squirrel cage, but rather than filter in layers I used eight 25x25x4 filters arranged in an octagon for a total of 35 sq. ft of filter area not counting the pleats which I do not know off hand. I installed it in the middle of the room with ducts moving the filtered air out to the edge of the shop so that the air was always circulating. With that much filter area there was no real vacuum pulling the dust through the filter making the filters much more efficient with the added bonus of having to change them out a lot less often.

I painted a van parked under this filter, and the filters were the color of the van immediately, and when done there was no dust anywhere, even on the floor around the van. I was happy with my contraption. I wired it so that it came on with the lights, in other words it was always filtering the air if I was there.

Even in the example above there is room for several more filters in the same space. Eliminate the plywood and make it all filter.

Larry

[eric burns]

Larry,
Do you have any pictures of what you built? I'd love to see how big this is.

[Larry Edgerton]

The base was a sheet of plywood, so basically a 4' octagon 27" tall. The fan was in the inside of the enclosure.

[Rod Sheridan]

Anyone ever try a electrostatic filter in their homebrew shop air cleaner?

Yes, I used an old Heathkit precipitator, worked well..............Rod.

[Phil Thien]

The base was a sheet of plywood, so basically a 4' octagon 27" tall. The fan was in the inside of the enclosure.

You posted a picture of it once, someone can probably find it via the search feature.

I think you also mentioned you were using filter charger on the filters, which also does wonders. It makes the filters sort of tacky. The finest dust can be grabbed with a rather coarse filter this way. And you can re-spray filters from time to time to give them new life.

[Ian Scofield]

Here's the pic:

[Larry Edgerton]

That is the one, but that pic is before I converted it to the 4" deep filters and added the ductwork. I have an attic full of cases of 4" thick industrial filters I bought from a diecast shop auction, so I am set for life on filters. I left that one at the old shop and have not built a new one yet.

[eric burns]

So with that design, the intake is through all the filters, is the exhaust out the top then?

[John McClanahan]

We have electrostatic filters, the kind that use a high voltage charge, in the furnaces at work. I take care of cleaning them. I'm not impressed with them. They seem to let a lot of very fine dust past.

John

[Larry Edgerton]

So with that design, the intake is through all the filters, is the exhaust out the top then?

Yes. To help visualize how this works take a dirty furnace filter and set your air at 10 psi. Blow on the filter from the dirty side toward the clean side. Now, set your air at 80 psi and repeat. You will notice that a lot of the dust that did not go through the filter at 10 psi will now blow right through. By eliminating the pressure differential between the two sides of the filter you make the filters more efficient. You will still be using the same amount of filter material in the end, but you will be catching more of the fines that higher pressure/vacuum would be pulling through.

I have heard the argument that an ambient air filter just keeps fines suspended, but I am not buying it. Possibly on a small system that is pushing air at a greater velocity, but with a large filter area air velocity is down to almost nothing. I had a filter on the duct exits and I never had to change it. They claim that it is best to catch dust at the source, which I do not disagree with, but in the real world it is just not possible to catch all of the dust from any machine. This takes care of the rest.

In my new shop I am going to increase the filter area to somewhere in the neighborhood of 100 feet, again not counting pleats. I am in a temp shop set up in a 3 car garage right now, and I really miss my filter system. If money just grew on trees...........

Larry

[Phil Thien]

I have heard the argument that an ambient air filter just keeps fines suspended, but I am not buying it.

Correct, nobody should buy that, it is a load of carp.