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18th April 2024, 02:18 PM #1
Air cleaner and directed clean airstream blower
Years and years ago we had a ducted aircon that originally came from the Ark when Noah had finished with it. It was superseded by split systems years and years ago too. Being me, I wanted to clean out the ceiling, but this required making a new big manhole to bring the ducted system down in parts. This I did ages ago too. I chucked the splitter box but hung on to the two blower units and replaced their cords with new cord with plugs. The amount of air these put out led me to believe I could use them for room air cleaners. They each have two squirrel cage blowers. At first I put a G4 filter on one and it caught quite a lot of muck! I was surprised. Considering I have a good DE that vents outside and it runs for quite some time after jobs. I like the blower because it is cheap to run and super quiet and I have ducting I attach to provide airstreams around the workshop as I need. For years I have been using it as a room air filter in this configuration, realising that the G4 was less efficient on smaller particles. I used to leave it a long time between cleans as it didn't seem to affect the airflow much and would have become a bit more efficient.
Recently I decided I wanted to see if I could add a finer filter, realising that the vacuum tests I did years ago said it would be marginal. Firstly I went off half cocked and bought an anemometer before reading BobL's thread on measuring airflow. Then I continued to ignore this information and measured the airflow at the two internal rectangular exhausts of the fans (the airflow at the circular ports was just to difficult to use). I came up with very conservative averages for airspeed at both ports and went ahead and calculated a very conservative 830cfm with no filter attached. This seemed in the ballpark of reality for a ducted aircon blower for a 50sqm residential room area. Anyway I had a filter company make up a cardboard-framed pleated F7 filter to nest in the back of the blower. They calculated a 50pa drop off for this sized filter. Today the filter arrived and I did up some more numbers. The capacity with just the dirty G4 prefilter in place was ~680cfm, with the F7 alone it was 487cfm and with both nested together it was 440cfm. For my workshop of 3700 cubic foot empty space this is a full exchange every 8.5 minutes. But this is to be run only after the room has had a good scrubbing with my dusty. I'll probably tick it over for a couple of hours after work.
If I had the room to mount the second one I would get it up and running too, but I don't, so I have a spare blower unit if anybody in Brisbane wants to do a similar thing. I'll get a sparky to look it over and test and tag it first.
IMG_0755.jpgmemento mori
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18th April 2024 02:18 PM # ADSGoogle Adsense Advertisement
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18th April 2024, 05:18 PM #2.
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That should be OK for cleaning up after the dusty and prepping the workshop for applying finishes etc. Ideally you want to capture escaping fine dust before it settles out because then just walking thru the workshop, moving stuff around or cleaning up just fluffs the settled dust up off surfaces.
My shed is slightly smaller than yours and my air filter is 800 CFM but I get very to close outside average dust concentrations anyway by just running the DC for a few minutes after the last major dust making activity.
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18th April 2024, 06:00 PM #3
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19th April 2024, 09:20 AM #4
One of my reasons for wanting to improve the scrubbing efficiency of the cleaner is that I had to recirculate DE air this summer (although I have very good and large pleated filters and plastic bags). The heat and humidity was just so oppressive this year. If it was better climatic conditions I would probably install the blower in a window. Question about that, would it be more efficient to blow out workshop air or blow in outside air? If this humidity visits again next summer it might be time for another aircon, though I don’t know how they cope with the volume of ambient dust.
memento mori
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19th April 2024, 09:42 AM #5.
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It's usually better to suck dusty air out than blow outside air in.
BUT
If there's only one air inlet to the shed eg a door, and the inside shed air is not stirred up this can create a reduced dust tunnel between the air inlet and the outlet while the rest of shed remains dusty.
Multiple air inlets can help mitigate this.
Something like pedestal fan can help stir inside shed air and help keep fine dust suspended so that it can be extracted rather than settling.
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