I'm in the process of setting up a 20x20 foot shop in my basement. There's
not a lot of ventilation down there--not even an outside entrance--so I
want to keep the air as clean as possible. That said ...

A guy I work with just gave me a never-used whole house fan (24" diameter).
I don't need it for its intended use, so I'm thinking about making a
downdraft sanding table / air filtration device out of it. I don't know how
many CFM this thing will move, but if it's anything like the one we had in
our old house, I think it will do the job.

I'm considering a design like this
http://www.woodcentral.com/shots/shot361.shtml with a timed switch.

So ... before I embark on this project ... can anybody tell me why this is
a bad idea? I'm grateful for any wisdom you can toss my way.

Jim Brown in PA

On Wed, 06 Jul 2005 18:37:16 -0500, the opaque Jim Brown
clearly wrote:

I'm in the process of setting up a 20x20 foot shop in my basement. There's
not a lot of ventilation down there--not even an outside entrance--so I
want to keep the air as clean as possible. That said ...

A guy I work with just gave me a never-used whole house fan (24" diameter).
I don't need it for its intended use, so I'm thinking about making a
downdraft sanding table / air filtration device out of it. I don't know how
many CFM this thing will move, but if it's anything like the one we had in
our old house, I think it will do the job.

I'm considering a design like this
http://www.woodcentral.com/shots/shot361.shtml with a timed switch.

So ... before I embark on this project ... can anybody tell me why this is
a bad idea? I'm grateful for any wisdom you can toss my way.

The motor most likely isn't rated for hazardous duty like a dust
storm, Jim, so it'll likely burn out very early. Hopefully it won't
cause a fire while doing so. Use it to ventilate the shop, not the
sanding table. Figure 800-1,000 CFM.

I had a 30" 2-speed and adored it in the hot summer months in LoCal.
I could come home after work, 90F inside the house, and in 15 minutes,
the inside air matched the 75F outside air. It was used as a whole
house fan, BTW.


-
Better Living Through Denial
------------
http://diversify.com Dynamic Websites, PHP Apps, MySQL databases

Larry Jaques wrote in
:

On Wed, 06 Jul 2005 18:37:16 -0500, the opaque Jim Brown
clearly wrote:

I'm in the process of setting up a 20x20 foot shop in my basement.
There's not a lot of ventilation down there--not even an outside
entrance--so I want to keep the air as clean as possible. That said
...

A guy I work with just gave me a never-used whole house fan (24"
diameter). I don't need it for its intended use, so I'm thinking about
making a downdraft sanding table / air filtration device out of it. I
don't know how many CFM this thing will move, but if it's anything
like the one we had in our old house, I think it will do the job.

I'm considering a design like this
http://www.woodcentral.com/shots/shot361.shtml with a timed switch.

So ... before I embark on this project ... can anybody tell me why
this is a bad idea? I'm grateful for any wisdom you can toss my way.

The motor most likely isn't rated for hazardous duty like a dust
storm, Jim, so it'll likely burn out very early. Hopefully it won't
cause a fire while doing so. Use it to ventilate the shop, not the
sanding table. Figure 800-1,000 CFM.

I had a 30" 2-speed and adored it in the hot summer months in LoCal.
I could come home after work, 90F inside the house, and in 15 minutes,
the inside air matched the 75F outside air. It was used as a whole
house fan, BTW.

Thanks, Larry. Had one in a house we rented in SC, and it was great in
the spring and fall ... the louvres were rather noisy but tolerable in
short bursts. There was another fan in the other end of the attic to help
the hot air on its way out. Here in northeast PA we don't have as much
need, and I'd have to get a louvred ceiling kit for it, so it's not worth
the trouble to use as a whole house fan.

This basement is a whole 'nother story ... two tiny windows in one end of
the place (one leading to the coal bin), no door to the outside, and when
we bought the house, no straight shot down the stairs, so forget about
even getting a sheet of plywood down there. Electricity? One outlet and
four single-bulb lights for more than 2000 square feet. We added a door
from the garage to the cellarway, so at least we can get 4x8 sheet goods
up and down the stairs now. But there aren't lot of options for
ventilation ... hence my interest in pulling some of the dust out of the
air. I didn't like working out of my garage, but I miss being able to
raise the doors and fire up the leaf blower ...

The motor most likely isn't rated for hazardous duty like a dust
storm, Jim, so it'll likely burn out very early. Hopefully it won't
cause a fire while doing so. Use it to ventilate the shop, not the
sanding table. Figure 800-1,000 CFM.

Not disagreeing outright but don't underrate the environment a whole house
fan has to live in (hot, insulation, dusty). This is probably a better
application for a squirrel cage blower but I have seen several examples of
sanding tables and dust filtration systems made from these fans.

In article ,
Jim Brown wrote:
I'm in the process of setting up a 20x20 foot shop in my basement. There's
not a lot of ventilation down there--not even an outside entrance--so I
want to keep the air as clean as possible. That said ...

A guy I work with just gave me a never-used whole house fan (24" diameter).
I don't need it for its intended use, so I'm thinking about making a
downdraft sanding table / air filtration device out of it. I don't know how
many CFM this thing will move, but if it's anything like the one we had in
our old house, I think it will do the job.

I'm considering a design like this
http://www.woodcentral.com/shots/shot361.shtml with a timed switch.

So ... before I embark on this project ... can anybody tell me why this is
a bad idea? I'm grateful for any wisdom you can toss my way.

The kind of fan you have is designed to move large volumes of air against
virtually -zero- resistance. OK for an "air cleaner", not so good for the
sanding table. (squirrel-cage blowers -- like the woodcentral pictures show
do a _much_ better job of moving air against some resistance.)

It needs 3-4 sq ft of "unrestricted" air intake, and the same for the outflow.

For air filtering:
Using 'el cheapo' fiberglass filters, figure minimum 50% more cross-section.
Using 'high grade' pleated ones, double the original numbers. at least.

In addition, you need the filters 'far enough' away from the fan itself, that
it draws relatively evenly through all the filter surface, *not* just the
area directly in front of the blades.


With elcheapo filters, I'd go for something like 4 16"x20" ones, spaced
about 3' in front of the fan.

On Thu, 07 Jul 2005 06:25:53 -0500, the opaque J Brown
clearly wrote:

This basement is a whole 'nother story ... two tiny windows in one end of
the place (one leading to the coal bin), no door to the outside, and when
we bought the house, no straight shot down the stairs, so forget about
even getting a sheet of plywood down there. Electricity? One outlet and
four single-bulb lights for more than 2000 square feet.

The evidence makes it clear that you should simply make a proper
dungeon out of the basement and build a REAL shop out back.


We added a door
from the garage to the cellarway, so at least we can get 4x8 sheet goods
up and down the stairs now. But there aren't lot of options for
ventilation ... hence my interest in pulling some of the dust out of the
air. I didn't like working out of my garage, but I miss being able to
raise the doors and fire up the leaf blower ...

Heh heh heh.
I need to do that again, too. I just clea^H^H^H^Hstraightened up the
shop and need to finish blowing out what didn't get sucked up by the
DC or swept up. While the floor sweep is a definitely nice addition to
the DC, a leaf blower gets into those crevices that the brooms and
vacs miss.


-
Better Living Through Denial
------------
http://diversify.com Dynamic Websites, PHP Apps, MySQL databases

(Robert Bonomi) wrote in
:

In article ,
Jim Brown wrote:
I'm in the process of setting up a 20x20 foot shop in my basement.
There's not a lot of ventilation down there--not even an outside
entrance--so I want to keep the air as clean as possible. That said
...

A guy I work with just gave me a never-used whole house fan (24"
diameter). I don't need it for its intended use, so I'm thinking about
making a downdraft sanding table / air filtration device out of it. I
don't know how many CFM this thing will move, but if it's anything
like the one we had in our old house, I think it will do the job.

I'm considering a design like this
http://www.woodcentral.com/shots/shot361.shtml with a timed switch.

So ... before I embark on this project ... can anybody tell me why
this is a bad idea? I'm grateful for any wisdom you can toss my way.

The kind of fan you have is designed to move large volumes of air
against virtually -zero- resistance. OK for an "air cleaner", not so
good for the sanding table. (squirrel-cage blowers -- like the
woodcentral pictures show do a _much_ better job of moving air against
some resistance.)

It needs 3-4 sq ft of "unrestricted" air intake, and the same for the
outflow.

For air filtering:
Using 'el cheapo' fiberglass filters, figure minimum 50% more
cross-section. Using 'high grade' pleated ones, double the original
numbers. at least.

In addition, you need the filters 'far enough' away from the fan
itself, that it draws relatively evenly through all the filter
surface, *not* just the area directly in front of the blades.


With elcheapo filters, I'd go for something like 4 16"x20" ones,
spaced about 3' in front of the fan.


I think go this route ... make a filtered air cleaner. The sanding table
can come later, either with the DC or a squirrel cage. Thanks for the
advice. When I get it done, I'll make a report.