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Building DIY Air Filtration Unit From Old Furnace Blower

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Forum topic by HorizontalMike posted 10-05-2017 08:19 PM 1356 views 0 times favorited 23 replies Add to Favorites Watch
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HorizontalMike

7605 posts in 2692 days


10-05-2017 08:19 PM

Topic tags/keywords: air filtration diy blower fan wiring schematic drawing

Well, I am finally getting around to this, after replacing/upgrading one of our two AC Heat Pump/Heater/Furnace units. Been long enough that I don’t remember if it was 2yr, 4yr, or longer ago. All I know is that it has been way too long! You’d a thought I was “Procrast-A-Didgitator of the Year!...” ;-)

Been trying to follow Bert's efforts from a couple of years ago. While Bert had some great images of his DIY Air Filtration Unit, it seemed to lack any detailed measurements, that I am anal about needing, for me to get started… Hence my several year “Procrast-A-Didgitation”... Yeah, yeah, yeah,... I know… ...I know…

So this is what I have thus far. Got the Blower pulled and reasonably cleaned (furnace is +20yr old). Had major rust issues because original owner “over-sized” his furnace/AC needs (used a 2-ton on each of two stories of 720sqft). This is why it eventually rusted out.

QUESTIONs:
  • What else do I need in the way of external switches,
  • While +40-45yr ago I used to be an electrician, never got into heating and AC, so how do I get this thing wired? BTW, have 240v wired in shop already.

I have roughed out what I think I need in the way of 3/4” plywood cuts, but amenable to alterations as needed. BTW, I plan on dado-ing slots for 1/8in hard-board dividers for the filters in each of their positions.

Looking at the switch above, can/should I use the “white” line in the 10-3+gr cable (below) as my “blue”(purple) run to my switch, in order to get my 2-speeds from the blower? The switch will be piggy backed on to an existing 240v outlet (with my jointer).

-- HorizontalMike -- "Woodpeckers understand..."


23 replies so far

View AandCstyle's profile

AandCstyle

2855 posts in 2035 days


#1 posted 10-05-2017 09:39 PM

Mike, I reused a 120v furnace blower to make an exhaust fan about a year ago. I didn’t use any switches; I just plug it in when needed. The motor will probably have 3 color coded sets of 2 wires. Each set will run the blower at a different speed. A knowledgeable person could probably tell you which color would likely yield which speed, but I am not that person. Have fun with your project.

-- Art

View Rick_M's profile

Rick_M

10243 posts in 2158 days


#2 posted 10-05-2017 09:47 PM

I’m not sure if the colors are universal but …
Green = ground, white = common, black = high, blue = medium, red = low.
So white + red will be low speed, etc.

If you want to use all 3 speeds.

-- http://thewoodknack.blogspot.com/

View AandCstyle's profile

AandCstyle

2855 posts in 2035 days


#3 posted 10-05-2017 09:49 PM

^^^ What Rick said. :)

-- Art

View GR8HUNTER's profile

GR8HUNTER

2731 posts in 490 days


#4 posted 10-06-2017 12:35 AM

I am very happy with my 120v blower ….I designed it around 20×20 filters :<))

-- Tony Reinholds,Pa. REMEMBER TO ALWAYS HAVE FUN

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Holbs

1688 posts in 1807 days


#5 posted 10-06-2017 01:44 AM

keep us updated, Mike. I almost went the same route as you. Found a 5500 cfm swamp cooler that initially wouldn’t work that I was planning to use as an air cleaner (3 sides better than 1 or so my thinking went) for $10 at an auction. Surprise surprise, just cleaned off the motor contacts and whalla…operational. Kept as swamp cooler duty because…well…this thing is so awesome :) When it comes time, I do plan on converting it to an air cleaner though.

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter

View JBrow's profile

JBrow

1233 posts in 698 days


#6 posted 10-06-2017 03:37 PM

HorizontalMike,

I will defer to Rick_M, but if his wiring key does not work, I will dig through my papers and try to locate a wiring diagram for a different application but which ultimately switched a HVAC furnace blower on and off. An HVAC technician prepared the diagram.

I really wanted to mention that rather than a dedicated air cleaner, the furnace blower could be outfitted in a table with an enclosed base and a perforated top. Air flow would thus be directed through the top into the cabinet, filtered, and then exhausted. The end result would be a downdraft sanding table. When not sanding and the unit left on, air from the shop would be drawn into the table and filtered. The air intake would be well below head-height and thus direct dust downward away from the breathing zone. Dust kicked up at the floor would have a long way to go to reach the head-height breathing zone. If the table is on casters, it be moved out of the way and if it overall height matches that of the table saw, it could also serve as an infeed support table for the table saw.

This style of downdraft sanding table works reasonably well at capturing sanding dust, although when sanding some dust escapes into the air. Also the load on the filters is significant and requires frequent cleaning while sanding to maintain air flow. Therefore careful design could help make cleaning the pre-filters faster and easier.

One last thought for anyone wanting to lay hands on an old furnace blower is that I found HVAC companies will give away for free furnace blowers from units they remove from a customer’s building.

View GR8HUNTER's profile

GR8HUNTER

2731 posts in 490 days


#7 posted 10-06-2017 05:03 PM

I really wanted to mention that rather than a dedicated air cleaner, the furnace blower could be outfitted in a table with an enclosed base and a perforated top. Air flow would thus be directed through the top into the cabinet, filtered, and then exhausted. The end result would be a downdraft sanding table. When not sanding and the unit left on, air from the shop would be drawn into the table and filtered. The air intake would be well below head-height and thus direct dust downward away from the breathing zone. Dust kicked up at the floor would have a long way to go to reach the head-height breathing zone. If the table is on casters, it be moved out of the way and if it overall height matches that of the table saw, it could also serve as an infeed support table for the table saw.

This style of downdraft sanding table works reasonably well at capturing sanding dust, although when sanding some dust escapes into the air. Also the load on the filters is significant and requires frequent cleaning while sanding to maintain air flow. Therefore careful design could help make cleaning the pre-filters faster and easier.

- JBrow

I would of rather done this …BUT to small shop anyways :<))

-- Tony Reinholds,Pa. REMEMBER TO ALWAYS HAVE FUN

View bigJohninvegas's profile

bigJohninvegas

369 posts in 1240 days


#8 posted 10-06-2017 05:36 PM

I used a wood smith plan for mine and it worked great. I am not sure about the size of your fan motor fitting it, but as you said you already have the roughed out. If I can find the pdf. I will attach it, but this link shows the joinery used.
http://www.houtdraaien.com/wp/wp-content/plugins/downloads-manager/upload/ShopAirFilter.pdf

I have a single speed blower, and found this timer switch at Home Depot that works well for my filter.
Not sure about what to do with a multi speed motor.
With this switch, the six buttons will turn it on for the marked time. big button will turn it off, or on to the last time that was selected.

-- John

View oldnovice's profile

oldnovice

6295 posts in 3145 days


#9 posted 10-06-2017 06:01 PM

I am considering a similar build as soon as I find a used furnace blower.
There are a lot on eBay and Amazon but I think one of the HVAC shops may have them too!
I would like a variable, or at least, multispeed blower.
I am going to make a removable top that covers a 1/4” piece of perforated tempered hardboard (with supporting underside braces) and a multi-filter system.
The top can then be removed to one of the sides and I have a sanding dust collection station.
With top in place one of the sides will be open, the side with the filters, turn this into an air cleaner.
This means that the height, for standing while sanding, must be at least as wide as it is tall …. correct?

-- "I never met a board I didn't like!"

View HorizontalMike's profile

HorizontalMike

7605 posts in 2692 days


#10 posted 10-06-2017 08:17 PM

Well I picked a 3/4×4 x 8 of ply and one of 3/16 hardboard. Got it roughly quartered using a 1×4 and my circular saw. Finishing touches will come from the TS for the ply and the scroll/jig saw for the hardboard frames. Sure got my dose of sawdust today!... 8-(

I like those sliding panels, that’s pretty slick. I do not have the shop real estate to build a free standing down-draft table, so that idea won’t work for me. I still have to be able to get my Harley in and out, as well as turning it around. I basically block the bike in, when WW-ing and then scoot my WW-ing equipment out of the way when I’m in bike mode.

Still considering how I will mount the blower and make it install-able/removable after the box is built. Thinking about mounting it on a sliding panel, to slide in/out like the AC filters only beefier.

I ordered this switch because my blower motor is 240v 2-speed. This will let me have two speeds and an OFF. I plan on mounting unit high, maybe along the wall(~8-10ft) above my current DC setup. I still have some armored 10-4 wire left, so I am thinking of mounting the switch next to my jointer 240v outlet and piggy-back off of that box which is ~36in. off the floor right next to the walk-in door.


New Rotary Three(3) Position Switch Power Ignition Selector Switch

-- HorizontalMike -- "Woodpeckers understand..."

View Fred Hargis's profile

Fred Hargis

4640 posts in 2271 days


#11 posted 10-06-2017 08:41 PM

Good way to switch it. I had one that had 4 speeds, but i only used the lower 2 in a less-clever way than you are doing.

-- Our village hasn't lost it's idiot, he was elected to congress.

View oldnovice's profile

oldnovice

6295 posts in 3145 days


#12 posted 10-07-2017 06:06 AM

Mike, that only has a 10 amp rating.
Is that enough?
Many year ago I worked for a company that made those kind of selector switches and they are pilot duty selectors meaning that the current level is low, not intended to switch motor directly.
Our competitors, Allen Bradley, Cutler Hammer, Square D all had similar ratings and I have never heard of this, Ace Crew, company.
Look at this motor control from Allen Bradley not pilot duty selector.

-- "I never met a board I didn't like!"

View HorizontalMike's profile

HorizontalMike

7605 posts in 2692 days


#13 posted 10-07-2017 10:22 AM


Mike, that only has a 10 amp rating.
Is that enough?
Many year ago I worked for a company that made those kind of selector switches and they are pilot duty selectors meaning that the current level is low, not intended to switch motor directly.
Our competitors, Allen Bradley, Cutler Hammer, Square D all had similar ratings and I have never heard of this, Ace Crew, company.
Look at this motor control from Allen Bradley not pilot duty selector.
- oldnovice

The way I understand it, the switch is rated at 10amps for 660v = 6600watts
And my motor is rated at 1.70amps for 230v = 390watts

”...One (1) Brand New Rotary Three-Position Selector Switch
Contact Rating: 660V/10A, DC and AC…”

.
.
.

-- HorizontalMike -- "Woodpeckers understand..."

View Warren's profile

Warren

3 posts in 165 days


#14 posted 10-07-2017 01:09 PM

View oldnovice's profile

oldnovice

6295 posts in 3145 days


#15 posted 10-07-2017 05:26 PM

Mike, the following is from Carling Technologies will clear up my cumbersome remarks from before.

”The voltage rating is a function of a switch’s ability to suppress the internal arc that occurs when a switch’s contacts open. The voltage rating specified on Carling Technologies’ switches represents the maximum voltage allowable for the switch to function properly at the rated current. The amp rating of a Carling switch is the maximum current in amperes the switch will carry continuously. So, in the example below the maximum amp rating for this switch at 250 volts AC (VAC) is 10 amps; the maximum amp rating at 125 volts AC for the same switch is 15 amps.

Switches that are going to be subjected to high-inrush inductive loads, such as an AC motor, will often be rated in horsepower in addition to volts and amps. This rating reflects the amount of current the switch contacts can handle at the moment the device is turned on. An AC motor will draw up to eight times its running current when first turned on or when held stationary while energized (stalled rotor). The switch in the example below would be rated for use with a 3/4HP motor at 125 through 250 volts AC.”

-- "I never met a board I didn't like!"

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