To begin with, Ametek,
the manufacturer of the motors in most systems on the market states specifically in their
warranty "typical signs of abuse [including] dirty motors, failure of which was
caused by inadequate filtration will not be considered in-warranty failures"4.
In other words, the designers of central vacuum systems are required to adequately protect
the fan blades of the motor from debris or risk being out of warranty.
There are two ways central
vacuum manufacturers filter the dirty air coming into the central canister. The
"cyclonic system" literally creates a cyclone to move debris toward an exhaust
tube.
The problem is this leaves
the motor exposed to the particles not purged by this motion. The filtered system uses a
porous receptacle to catch all debris, eliminating accumulation on the fan blades. The
problem: How do you provide adequate filtration to protect your motor without reducing
vacuum performance through restricting the airflow? What are the implications both short
term and long term? Your investment decision should be influenced by these all-important
facts.
See M.D. Central Vacuum
System cut-away below.
CYCLONIC SYSTEM
Contrary to what a few manufacturers claim, none achieve a "true cyclonic", in
which ALL filtration is achieved by centrifugal force and gravity to separate the
impurities from the intake air. Vacuflo and Vac-U-Maid come very close to being "true
cyclonic", but both have some type of additional filter, as mentioned in their
service manuals. Vacuflo says, "A guard screen is located directly above the dirt
pan inside the power unit. It should be inspected and cleaned occasionally. This is to
prevent such things as carpet fiber, cloth, etc. from getting into the motor's impeller
blades. A buildup of dirt or other larger, clogging-type material may result in loss of
vacuum"5. Their service manual goes on to say that, "much
excessive, loose lint and nap, normal in all new floor coverings, is removed in these
early cleanings, and some will tend to settle on the screen, allowing a buildup that will
impair the suction power unless removed."
Thinking they are buying a
"true cyclonic" system, many homeowners don't properly maintain the added
filters. This severely limits the efficiency of the vacuum and the life of the motor.
In their sales literature,
Vac-U-Maid states that they do have a metal screen but, "the pores of this metal
screen are sufficiently large to insure that no plugging results from normal use.
Therefore, you have constant airflow and no loss of cleaning ability." This
sounds impressive but their service manual says, "if the screen becomes clogged
with lint and rug fibers, it will decrease your vacuum power to a point where you are
unable to clean properly due to the decrease in air flow."6. Systems
sold as cyclonic are still using filtration to protect the motor. Let the buyer beware,
this confusion has lead to owners of these systems being dissatisfied with their system's
power and the motor's life.
While cyclonic action does
remove the heavy particles, the light fibers and dust are emitted through the fan
blades creating havoc with the motor and decreasing its life. Vacuflo claims that
their system will "maintain up to 98% efficiency. The remaining 2% consist of
small particles which are exhausted outside"7. That's why their
service manual states that when low suction exists, "the exhaust line may be
clogged." Their manual also states that
"overfilling of the unit may
cause motor damage."8
Again, VAC-U-Maid's manual
states, "overfilling could cause debris to be drawn into the impeller blades which
may severely damage your power unit." In all the literature, the one stated
advantage of cyclonic filtration is that there are no replacement filters or bags to buy.
However,
$15.00 per year is a lot less than the cost of replacing or repairing the entire unit
prematurely.
Be they cloth, foam,
geotextile, self-cleaning, or never-clog cloth, all cyclonic systems use filters to try to
protect the motor. The cyclonic action does eliminate a high degree of the debris; but
fine dust and lint need to be kept from the motor for thorough protection.
To maintain maximum
performance, some manufacturers like Hoover recommend that "the filter should be
cleaned every time the dust container is emptied."9 Easy-Flo suggests,
"To extend the life of your vacuum change your filter."10 Beam
states, "it is recommended that once a year the filter should be cleaned
thoroughly."11 Again, in the trouble-shooting section of Beam's manual
you will see as the number one remedy for loss of suction, "clean out dirt
receptacle. Inspect and brush off filter."12
Finally, most cyclonics must
be vented outside the living areas, "because it eliminates the very fine dust and
bacteria not trapped by the system's filter."13 Let's look again at
what Ametek says: "If their filter is too porous, dirt and other foreign material
can build up on the fan blades over time." "A motor can handle a certain amount
of this," says Stormy Greer of Ametek, "but what really causes a problem
is when this material breaks away unevenly. When this happens, the vibration in the motor
increases. The high-speed operation of the motor makes balance critical and as vibration
increases, premature motor failures can result. This is one reason we are so concerned
about adequate filtration. The amount and rate of dirt build-up on the fans in an
inefficient design or unmaintained system can cause problems sooner than a customer
expects. When this happens, we all have a problem."
The build up of foreign
material in the motor over a period of time is a fact often ignored by the big-name
manufacturers. The main reason for this is that they expect their systems to only last
five or six years. At M.D. Manufacturing, we maintain that normal, residential usage
should provide at least twice that motor life.
FILTERED SYSTEM
It should be noted that filtered systems are, in theory, more restrictive of airflow
than cyclonic systems. As the trash receptacle fills up with debris, airflow will diminish
- despite one manufacturer's claim of a unit "designed to permit full air flow and
full cleaning power at all times."14
The key to filtered system's
superiority is designing a unit that protects the motor from damage while maximizing
vacuum power.
Some filtered systems cause
loss of performance far quicker than others. Those with longer continuous power often
support a paper bag with a cloth bag, which allows the paper bag to be made lighter and
more breathable. This is the method used by M.D. Manufacturing. Others, such as Nutone,
use a heavy porous paper bag which, "if the bag is filled, you will notice a
complete loss of vacuum."15 For added filtration; secondary filters
are often incorporated which act as a safeguard against bag breakage. Inadequate primary
filtering may require that you "clean secondary filters each time the bag is
replaced."16
The filtration system used by
M.D. Manufacturing is a paper bag supported by a tapered cloth bag. The tapering
adds surface area for greater particle distribution and less vacuum loss. Tests with
twenty pounds of flour did not significantly impede the flow of air .17 In
fact, many of our dealers have reported servicing units where the tank was filled to the
lid and still had good suction! Undoubtedly, there was airflow loss but because no debris
was getting to the motor, no damage was done to the unit!
Further observations of
testing with twenty pounds of flour revealed a turbulent airflow pattern created as debris
entered the trash receptacle. This means the filter actually "cleaned itself" as
the air swirled around. (You might like to try this yourself with our Acrylic Lid, Part
#97C. It's absolutely fascinating!)
We at M.D. will be the first
to admit that our bag filtering system will effect performance as the paper bag fills up
but we qualify that statement with the fact that properly maintained bag filtration
systems are the best for the performance and life of your system. Semi-annual
replacement of a paper bag makes a lot more sense than the loss of performance and motor
replacement costs on cyclonic systems.
For super-filtration, where
extremely fine particles are being picked up (such as aluminum oxide in dental labs,
plastic dust in circuit board manufacturing, or sanding debris in auto body shops and
marble polishing), a combination of the above systems has proven most effective. A
cyclonic separator is first installed to remove the large debris and then a separate paper
bag filtration unit catches the fine particles. A "micro-filter" can also be
installed which filters down to .1 micron at a 99.7% efficiency.18 This will
certainly minimize motor failure. Obviously, however, the finer the filter, the quicker
the loss of performance.
THE
M.D. CENTRAL VACUUM SYSTEM
 |
1. Air intake. The system of tubing goes from the wall inlet to this point.
2. 12-gallon double-bag tapered dirt receptacle only needs to be emptied around
twice a year.
3. M.D. Manufacturing's primary filtering consists of an inner porous 2-ply
disposable bag. The first layer is slick so the dirt falls to the bottom. The second is
where the fine particle filtering takes place. This is supported by a porous heavy-duty
cloth bag (blue). Notice the taper of the bags, which allows maximum surface area for
maximized airflow.
4. The air in this open area around the bag and near the motors is tremendously
cleaner than cyclonic models, thus protecting the fan blades from build up which causes
early failure.
5. The secondary filtering (4 stages of filtration in total) is made of breathable
foam and plastic fabric.
6. High performance motors in motor compartment are kept clean by the filtration
system above it.
7. Exhaust. While cyclonic models normally need to be vented outside, this
filtration system keeps the exhaust much cleaner without any need for venting outside. |
With these questions you can
arm yourself with a more thorough knowledge of how each manufacturer rates on filtration
and therefore on system longevity and efficiency. Know the product you are buying. Be
assured of its performance and intelligently evaluate the other products on the market!
We are confident at M.D.
Central Vacuums that you will find our products and service tops in the industry.
