We are planning to install a central vacuum system in the house we are
building to eliminate the dust which is causing Jim's sinus symptoms.
The store recommends something that precipitates the dirt by a cyclonic
action then puts the air with residual dust directly outside.  Does anyone
have any experience with this or other systems?  What sorts of tools would
you consider essential to vacuuming?  The store can put together a selection
of anything offered.  We do not have carpets or drapes, just floors and walls
and bookcases and the like.

20 responses total.

Cyclonic action.  Boy.  I think that is simply where you send the dirty
air into the periphery of a cylinder and draw it off from the center.  It
sets up a sort of hurricane action in the cylinder.  Since the center of
a hurricane has the lowest wind velocity it will also contain the least
debris.  All the heavy stuff falls to the bottom.  The light stuff will
exit along with the air.  You defiantly will want to exhaust this outside
your house since it will contain a lot of dust, pollen, and other light
stuff.  Vacuumed nuts and bolts will be found inside the canister ;-)

We use an Electrolux canister vacuum in our house with hard floors.
Uprights work best on carpets.  We have a floor brush that can
be reversed to clean area rugs and such.  We also have a little hand
brush that can be attached to the end of the wand for cleaning shelves
and I even use it to clean dust out of our keyboards.  It can be reversed
to a small wide-mouthed tool for vacuuming under cushions.  That's about
all we really use.

A separation device such as described above is called a "cyclone" and is
a common industrial device for cleaning air of particulates. The dirty
air is injected tangentially at the periphery (as Klaus says) and mostly
exhausted through a tube that protrudes into the center. Hower the *highest*
air velocity - and rotation speed - is near the *center*. This is the same
effect as in a tornado (or the skater spinning faster by pulling in their
arms). It is the higher central spinning velocity that does most of the
separation of the particles from the air. The particles migrate to the
outer walls, where they then slide down to the bottom and is collected.
No cyclone is 100% efficient so a portion of the lightest particles escape
it. 

We were told 99% of the solid matter dropped out.  I presume that does not
include lightweight and small particles (such as dust?).  The info mailed
Monday has not yet arrived from Livonia.
        I have used a floor brush, a round brush, and a wand when cleaning up
plaster and sawdust.  I think the other two brushless tools that came with
my mother's 1947 canister Electrolux are a wide one for carpets, and a narrow
metal one for furniture and/or drapes.  The brush I choose depends on the size
of the area to be cleaned and on the opening available to get at it.  I use
the wand to clean up around the table saw, and the round brush to get between
pieces of drywall.  I expect the wand would also work on cobwebs.  I am
apprehensive that we will have far too much suction and be vacuuming up things
larger than nuts and bolts, but at least they won't get blown outside.

Jim asks is this different from snow fencing.  Snow fencing has some slats,
it keeps snow off of the highway by making the air accelerate when it goes
through the fence and then decelerate a few feet after it, and at that point
the snow drops out and it causes a drift action.  So you can predict where
the drift will be.  SOmeone correct him.

There is a wake behind objects in an air stream where the air is turbulent
and moves in eddies, with zero and reversed flows. Objects in those
eddies tend to drop out. So, Jim is correct in regard to the consequences.

OK, I just found a web page showing how the cyclone separator works:
http://www.miningusa.com/deter/cyclone.htm  They are not good for final
filtration, however make good prefilters since they contain no filter
media to clog up and can be cleaned simply by emptying the debris out of
the bottom.  From the hits I got, I see they are commonly used in shops
to collect dust from dust generating equipment and as prefilters on engines
used in dusty environments, such as the Toyota Landcruiser and some of Honda's
industrial engines, etc.

We had a commercial cyclone in our senior chemical engineering lab at UM,
which I taught. It was a great cyclone but a lousy engineering teaching
tool because it was so efficient. Given that the material we separated had
to be non-toxic and non-flammable, we never found a way to measure the
fraction of the feed particulates that were not collected, as a function
of operating parameters (of which there aren't many - gas flow rate was
it), without building a after-collection device that would be much more
complex (and expensive) than the cyclone.

Why couldn't you feed it a known quantity of solids, then see what fraction
it had managed to collect?  1000g in, 800g collected => 80% efficient.

We were already at 99.9+ % efficiency. There is no way to measure the
difference from 100% with 2-3 significant figure accuracy. That does
matter, by the way. Don't look at the 99.9% - look at the 0.1%. 
Processing 10,000 pounds per day of particulates would lead to an
offsite release of 10 pounds per day. If that stuff is toxic, you
are in deep toxics. 

Ah!  Okay.  I take it that the cyclone was too big for "bubble it's output
through water" and similar stuff to be impractical. 

How about measuring the amount of stuff that got past it optically?  (Run
it's output through a long pipe, add a few mirrors & a laser, then watch
what happens to the beam.)  

The cyclone was 12 feet high and 6 feet in diameter. It was actually a
"multiclone", with some dozen smaller cyclones fitted to a header inside
the big shell. This was also a problem as the header and other parts
collected a lot of solids, which did not just fall out the bottom. Tests
could be done on it if one had litteraly tons of stuff to feed it so
that it could be brought to a steady state. We had no way to do that.
One could have used an optical esimation of particulate density in the
exhause, except there was nothing we could use that was very light and
would be evenly suspended in the exit gas stream. It would have been a
fire hazard to use, say, sawdust or wheat dust, and also a health hazard.

Oh well.  Sounds like you could optically monitor for breakdowns (dropping
efficiency) at best.  I was figuring on feeding it sugar, sand/rock dust,
or something similar and maybe running the test during a good rainstorm.

Fine sugar is explosive in suspension, sand/rock dust is hazardous (silicosis)
and the damn thing was inside the laboratory. [And we finally gave the thing
away, so further study is moot.... 8^}]

Klaus, we will check the website, hope it is text only as we are text only.
Today we biked to Leabu's.  He says all the central vacs use the cyclonic
chamber, at least the ones he knows about do.  He recommends Hayden.  They
also make most of the fittings and valves for other companies.  We should not
use it to vacuum either plaster dust or soot, they will both ruin the
canister.  He suggested a cheap shop vac for that purpose (we have a few to
use up, I am saving John Morris's for better things).  So we are back to other
things for while.  I will vacuum when Jim is not around.  Ristenbatt 
(www:ristenbatt.com) has lots of info at their website, and Hayden (Hayden.ca)
has lists of products with pictures that we cannot see.  Hayden bought out
Filter Queen ten years ago and is owned by Mr. Hayden.  Vacu-Flo advertises
their product as not having any messy filters to change (sort of like
focus-free cameras, I suppose) but Jean Leabu said that means the dust will
get into the fan instead.  We should put in a few cleanouts for when the wrong
things get vacuumed up and clog the angles in the system, and we should use
two 45s in stead of one 90 where possible.
        Hayden suggests that you buy as much power as you can afford (like the
100 watt receivers?) in order to be able to vacuum the car.  We don't.
        Imagine a 12' high vacuum cleaner!
        Leabu recommends Lamb motors, and from experience with repairs does
not recommend Hoover, Eureka or Nutone, they tend to have rivets fall off and
other common problems.
        House dust contains allergenic molds, mites and bacteria, say the
websites.  Mr. Leabu says he also has allergies, but for some reason the store
smelled of smoke.  He was very nice about it and came outside to talk.  He
seems to enjoy the business and had some interesting stories to tell.  The
only other store in town that handles central vacs sells only one model,
complete with all the parts, one size fits all (poorly, I presume), which is
rather more expensive.

See also www.geocities.com/Heartland/7400/vacuums.html
for 56 pages of comments from owners of central vacuums (and a few
Rainbow water filtered vacuums).  They suggest an outlet in the basement
and in the attic.  We could read Klaus's web page.

But you could no see the diagram of the cyclone separator. I also agree
that you should minimize the number of turns in your system and try to
use 45 instead of 90 degree elbows whenever possible.  However, a long
sweep 90 is the same as two 45's end-to-end with one less joint.  It is
also a good idea to check the fittings for internal imperfections, such
as gates and flashing, that could collect dust and dirt.  If you plumb
it out of standard 2" plumbing PVC, let me know.  I've got lots of spare
PVC left over from my project.

Thanks, Klaus, but I think we will use the standard 1 1/2 inch thin wall
stuff, it is cheap and fits more easily in the walls.  We might be able
to use some of your PVC for our plumbing, though (some year, not this one).
Good idea about checking for imperfections internally.  In the meantime, I
am using up shop vacs on the dust and as long as I vacuum a while before Jim
goes in the house, he is okay.  Now the smell of the acrylic adhesive on the
tape we are using on the vapor barrier (aluminum tape) is bothering him, but
it eventually outgasses and we are nearly done.  (It has gone much faster
since I ignored his statement that it was a very difficult job that only he
could do.  Little fingers are actually better at peeling the backing off. 
But I keep getting the equivalent of paper cuts).
        There is now condensation on our single-pane storm windows in the
mornings, but the house itself keeps warm overnight with the insulation.  
We hope to get our 1 by furring strips put on teh walls this month so we can
tape plastic over the windows until we get our R-3 double-glazing added.
        I read Jim your suggestions but he seems to be asleep, it is difficult
to sleep comfortably at night with a sprained back and I fixed him up with
a couple of pillows, sitting.

OK, keep my PVC collection in mind when you do plumb.  I have too much.
I would also look into going with larger than 1 1/2" thin wall.  Since
the wand and flexible hose are close to 1 1/2" dia. I would think that
having the whole system plumbed with 1 1/2" might make it pretty lossy.
A less restrictive system would require a smaller motor and generate 
less noise because of the smaller motor and less turbulence in the
plumbing while giving you the same or better suction at the wand.

(and use less electricity)

Actually it is 2" thin-wall, same o. d. as plumbing pipe but larger inside.
We will use standard stuff to fit standard fittings.  We are not worried about
loss in a small house with short runs, we are more worred about gettin g so
much suction that small heavy objects get into the vacuum.
        The Hayden company advises getting a model with a larger motor, they
are better made, have 'slow-start', will last longer, and have colored lights
that tell you that you have run it for so many hours that you should look at
the brushes before they wear down to the point of ruining other parts.
The noise will be below the porch and hopefully not a factor, but they do also
sell mufflers (for the exhaust air, in case it makes too much outside noise,
which nobody would hear with all the traffic on our street).  We will go with
sweep 90s or 45s, at most five turns in a run.  The model with the smaller
motor is not recommended by anyone, it wears out faster and only saves $50,
it makes sense only if you are a builder cutting costs.
        Zimm's in Livonia sells hose by the foot, the type without 24V wire
in it.  (The wired type is only sold in standard lengths and you need it to
run a power nozzle or if you want a switch in the handle to turn it off from
the open end rather than by unplugging it, in large houses where you may be
far from the inlet valve).  We can buy two short lengths and they couple
together airtight, in case we want to vacuum the attic with a long hose, or
the porch or the yard or....
        We will go look at stuff in Livonia when Jim's back is better.  In the
meantime he is supposed to be fixing a few phones (but his eyes appear to be
shut).  I am pleased that this morning we official gave up on fixing three
cheap tape players with fried parts, and I was allowed to donate them to the
Slauson school electronics class, which takes things apart and then recycles
the components when they are done.  You can drop them off there or at Tappan,
anything beyond fixable that has interesting innards.  The Hands-On Museum
and Leslie Science center also want take-it-apart things and may pick up.

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