Cyclonic and Inverted Filtration Methods;

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." 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." Believing that they are buying a "true cyclonic" system, many homeowners don't scrape screens or properly maintain the added filters, which severely impairs the efficiency of the vacuum and limits the life of the motor.

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". 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."

Whether they are 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; however, 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." Easy-Flo suggests, "To extend the life of your vacuum change your filter." Beam uses an inverted filter system and they state, "it is recommended that once a year the filter should be cleaned thoroughly." 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."

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." 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 constant build-up of debris in the motor over a period of time is 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.

Filter Bag Systems

Nybakke knows that the key to filtered system's superiority is designing a unit that protects the motor from damage while maximizing vacuum power.

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 (625k PDF). 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.

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.

To summarize, every central vacuum system needs a filtration system to protect the motor. And any filter you install (screen, cloth, foam, paper, etc.) will impede airflow in some manner. What makes one system better than another is its ability to minimize debris around the motor while maximizing airflow for vacuum power. At Nybakke, we believe that the M.D. Central Vacuum has designed a superior system that is the most powerful, efficient and with maximum longevity. We hope you'll give us a chance to demonstrate that to you.