Introduction to Built-in Vacuum Systems

Lindsay Manufacturing Inc

A built-in central vacuum system consists of several major assembles: The power unit and dirt collector; the tubing and wall inlets; and the cleaning tools.

The power unit and/or dirt collector can be constructed from plastic, fiberglass or metal and is usually mounted in a garage, basement, utility room, attic or any suitable space that is accessible for emptying the dirt canister and where the motor noise will be away from the living areas of the home. Most manufacturers have decided to rely on steel for housing the motor/blower and dirt collector, which although slightly more expensive to fabricate, imparts a reliability and strength plus resistance to heat and flame that is unobtainable in plastic or fiberglass. A metal motor housing is extremely desirable to help provide maximum cooling of the motor/blower unit by conducting the heat away from the motor so that it may be more easily dissipated by the cooling airflow. High motor temperatures tend to greatly reduce the brush and bearing life. Every 10° F rise in operating temperature will cut the motor life in half. Although some manufacturers state that their power units need not be vented outside of the home, all vacuum cleaners (including portables) regardless of the type of filtration system, pass some dust particles back into the atmosphere. Therefore, it is imperative that all power units be exhausted or vented to the outdoors. Some brands have no provision for outside venting.

The vacuum tubing and fittings may be made of steel , aluminum, or one of several plastic materials like ABS or PVC. For most installations plastic is recommended as the ideal material, not only because it is less expensive; but, it is easier to obtain a perfect vacuum seal and not as steel or aluminum when sand or hard particles are being moved. Standard ABS plastic tubing is not recommended because it will support combustion while PVC tubing just sublimes and will not support combustion. Over 85% of al central vacuum manufacturers recommend that 2′ outside diameter tubing be used with their systems. The rest use 1-3/4′ or 1-13/16′ tubing. Since the airflow loss in any tube varies in accordance to the 5th power of the diameter, a 1-13/16′ tube will have over twice the loss of a 2′ diameter tube. The smaller tubing is also more susceptible to plugging. Some building codes may require the use of steel or aluminum in places that may be subject o high fire hazards. The tubing can be installed under the floors, in walls or attics to connect the wall inlets to the dirt canister and power unit. If absolutely necessary it may be installed under concrete slabs, but extreme caution should be exercised to prevent crushing of the tubing and where the tubing projects through the slab, sufficient clearance between the concrete and tubing must be maintained to allow for the different rates of expansion and contraction. The wall inlets with their back-up plates may be constructed of plastic or metal and most are equipped with some type of low voltage switching device to turn the power unit on or off as needed. Most inlet face plates are made of plastic which is subject to heat warping and breakage. However, metal inlets are available, although they may be slightly more expensive they definitely have a longer service life. Most inlets require the use of a metal ring on the flexible hose cuff that plugs in to the wall inlet valve. The metal ring makes contact with electrical connections in the wall inlet to turn the power unit on or off. Better inlets have some type of electrical switch, which is definitely more reliable. The inlets should be installed on interior walls, at doorways, or in halls where they will not be blocked by furniture. Some may also be installed in ceiling or floors if necessary.

The flexible hose may be manufactured from many different materials; but most are made of some type of plastic with or without a wire wound core. Wire wound cores are not recommended because they lose their shape if kinked, stepped on or twisted and generally have a greater resistance to airflow than their non-wire wound counterparts. The length , inside diameter and smoothness of the inside of the flexible hose is very important to the cleaning ability of any central vacuum system. The high velocity air stream generated from the power unit can be severely retarded by using a hose that is too long, very roughly corrugated inside or that has too small an inside diameter. The wands may be made of plastic, aluminum or chrome plated steel. The best and more expensive metal wands have slotted ends where the pieces slide together to facilitate taking them apart. The best central vacuum system manufacturers have now standardized on a 1-1/4′ diameter, chrome plated steel, three piece wand with slotted ends and this is highly recommended. Some manufacturers now offer several lengths of wands, so that the wand length can be matched to the height and cleaning style of the user.

The set of cleaning tools usually consists of carpet tool, bare floor brush, dusting brush, upholstery tool and crevice tool, with some type of carrying caddy. These tools may be made of plastic or metal and vary greatly in price. There are also optional tools: such as, electric operated brushes, vacuum operated brushes, manually operated brushes wet pick –ups with squeegees, and animal care tools. The type of cleaning tool used with any cleaning system is very important and no one tool has proven to be the best for all types of carpet. Most sets of cleaning tools on the market today were designed to be used with portable vacuum systems. Most central systems move air at a much higher velocity than can be generated by portables. Therefore, the tools designed for portables cannot clean as well as those tools that have been specifically designed to utilize the greater airflow.

A built-in central vacuum system has many advantages over the conventional portable vacuum cleaners.

    1. Deep cleaning ability- One of the greatest advantages comes from the stronger suction and higher velocity airflow that the large power units can generate. There is just no way that the large motor/blower units can be put on a portable and still have it portable. Unlike portables, most built-in systems have enough airflow to actually deep- clean carpets. That is, they not only can clean the lint and debris from the carpet surface, but they can remove the grit and dust that collects on the carpet backing, down at the base of the carpet fibers. This requires a very high velocity air stream, because the heavier a dust particle is for its size the higher the air velocity must be to pick it up.
    2. No dust recirculation with those central vacuum systems that are exhausted outside the building. (Not all systems have provisions for outside exhausting)- all of the air, dirt, smoke, even the odors that are picked up in the home are either deposited in the large dirt canister or exhausted away from the living areas. Unlike portables that are always filtering the air and spewing it back into your room along with the dust particles that are small enough to go through the filter bags, the central vacuum system completely removes everything it picks up from the room. The drapes, tables, chairs, walls, even the furnace air filter will stay cleaner longer since the central system is removing more of the dirt and not redistributing it about the home.
    3. Low noise level- the motor/blower noise is isolated from the living portion of the home, since the larger power unit is usually mounted in the garage, basement, or attic. Therefore, the ‘whispersilent’ airflow through the cleaning tool allows the system to be used without disturbing the other occupants. No need to worry about missing a telephone call, crying baby or favorite TV show while cleaning.
    4. Convenience- no longer is it required to haul a heavy machine around or up and down the stairs. No electric cords to tangle. The lightweight cleaning tools are very easy to handle and their low profile enables on to clean in those hard to reach places –like under the bed, couches and chairs.

    Just as with any product in demand, there are several built-in vacuum system manufacturers. However, like automobiles there is quite a difference between the various brands of central vacuum systems. The greatest difference lies in the type of filtration system built into the dirt canister. All models produced, however, fall into one of five types of filter categories. Since the different filter systems vary in price of production, some manufacturers produce more than one type.

    The type of filter system is very important- because a clogged filter can severely reduce the airflow. The cleaning ability of any vacuum system is dependant on the high velocity air stream that is moving dirt and dust from the house to the container. Therefore, anything that will tend to retard this airflow is detrimental to cleaning ability.

    Category 1 Filtering System: Cloth Bag

    Airflow brings the dirt /dust into machine and deposits it into a cloth bag. The cloth bag filters out the dirt and most of the dust. Very fine dust, as with all vacuums passes through the bag and is exhausted. As the cloth bag fills with dirt / dust , the tiny pores in the bag (which allow the air movement) begin to plug. As the holes are plugged the airflow diminishes. In order to maintain a strong airflow the bag should be emptied and shaken often. In addition, to open up as many pores as possible the bag should be washed after using one or two months. The pores in cloth bags are generally larger than paper bags and therefore, usually do not stop up quite as rapidly. However, the airflow is restricted by having to pass through the mass of heavy debris deposited in the bag. To clean the unit requires that the bag be removed and dumped, then shaken and/ or washed and dried before replacement.

    Category 2 Filtering System: Paper Filter Bag

    This category works on the same principal as Category 1. The difference being , that the paper bag generally is finer textured than the cloth bags and therefore the tinier holes tend to plug up faster, but to offset this the paper bag usually has a larger surface area , and therefore a greater number of tiny pores. Thus, it takes longer ( in ratio) for the airflow to diminish. Paper bags are of the disposable type and you don’t have to shake or wash them; but this brings on the obvious disadvantage, that you must buy new bags. If the unit in an average home is kept operating at approximately 80% cleaning efficiency the cost for bags annually could approach the cost of the unit. To clean the unit one simply removes the old bag and replaces it with a new one.

    Category 3 Filtering System: Inverted Bags or Foam Filters

    Airflow brings dust/ dirt into unit at approximately mid-machine. Heavy debris tends to fall into bottom of canister due to gravitational forces. The dust and lighter dirt is pulled upward by the force of the air stream and is separated by an inverted cloth bag or foam plastic cylindrical filter. Not having the heavy debris helping plug up the holes in the filter medium allows you to clean longer before the airflow diminishes to the point where it is necessary to shake or wash the filter. This unit is sometimes considered superior to Categories 1 and 2, but in reality may not be as good as Category 2, since most of the light debris will still reach the filter areas which is generally of smaller size than Category 2 and would therefore more quickly plug the pores and diminish the airflow. To clean the unit one simply removes the bottom canister, shakes and/ or washes and dries the filter bag or plastic foam, then dumps debris into trash receptacle.

    Category 4 Filter System: Cyclonic Separation and Inverted Cloth Bag or Plastic Foam Filter

    Airflow brings debris into unit at approximately mid-machine and inlet nozzle directs the flow downward as well as in a cyclonic (swirling) action around the inside of the canister. Centrifugal force carries the larger particles to the sides of the canister where they are trapped by a plastic cone. The finer and lighter particles are then filtered out of the air stream by an inverted cloth bag or foam plastic filter. This unit is considered superior to Categories 1,2, and 3 in that only the finest dust ever reaches the cloth or foam filter and therefore it takes longer (in ratio) for the pores to plug over a period of time and it is important to clean the filter regularly. Filter should be washed every two to three months. To clean unit one simply removes the bottom canister, shakes and/or washes and dries the filter, then dumps debris into a trash receptacle.

    Category 5 Filtering System: Filterless Cyclonic

    As in Category 4, air flow is directed into a cyclonic (swirling ) action around the inside of the canister. Centrifugal force carries the dirt and dust particles to the sides of the canister where they are trapped by a series of cones or stand pipes. Above the cones air passes through a very porous metal screen which will catch any fine thread-like dust or lint particles. The pores of this metal screen are sufficiently large to insure that no plugging results from normal use. Therefore, you have a constant air flow and no loss of cleaning ability. To clean unit one simply removes bottom canister, brushes off metal screen, then empties canister into normal trash receptacle.


    Categories 1 through 4 exhaust no more fine dust than portable vacuums and technically do not have to be vented any more than portable vacuums. However, all vacuums exhaust dust and to this extent, we recommend venting in all cases. Category 5 exhausts only slightly more dust than the other categories and should also be vented.

    Ideal Central Vacuum Systems

    We recommend that the ideal central vacuum system for the average home (up to 3,500 square feet) have a power unit constructed of steel with a series motor drawing at least 11 amps on a fully cyclonic separator. The tubing and fittings on the wall should be of fairly heavy construction (tubing 1/16 inch wall, 2.0 inch outside diameter) (Fittings with ¼ inch wall-no builders weight). Wall inlet valves should be of metal with a positive action electrical switch for the low voltage (24 volts) remote control (no pin jacks). The hose should be between 25 and 30 feet in length, preferably nearer 25 feet and have an inside diameter of 1-1/4 inch with no wire windings. The tools should be designed to utilize the high velocity air produced by a central vacuum system and constructed of high impact plastic for rigidity/lightweight so they will not mar furniture.

    Typical Central Vacuum System Specification

    Furnish and install one central vacuum system consisting of a filterless cyclonic power unit and dirt canister capable of 110 inches H2O lift sealed vacuum and 110 CFM air flow through a 2 inch opening. System ducting shall consist of 2 inch outside diameter PVC tubing and appropriate heavy duty PVC fittings with WI-629X. Ivory colored, steel inlet valves and outside exhaust duct to be installed as depicted on the architectural plans. Power unit and wall inlets must have must have 24 volt remote control capability. Furnish one 25 foot flexible hose with 1-1/4 inch inside diameter and one CT-590 tool caddy. Tool caddy will consist of steel tool and hose hanger, combination bare floor and carpet brush, upholstery tool, oblong and round dusting brushes, crevice tool and chrome plated steel three piece wand set with vacuum relief slide.

    Household Dust


    Over the past few years more doctors and scientists around the world are speaking out about health problems associated with housedust.

    ‘Housedust’ is a catchall term. It may include such things as pet hair, mold spores, and pollen, parts of small insects, bacteria and much more. Everybody’s ‘housedust’ is different and the way people react to ‘housedust’ may vary. Many people who are allergic to one or more of the ingredients of ‘housedust’ may have any of the following symptoms: runny nose, sneezing, coughs, headaches, itchy eyes or hives to just name a few. Biologically, nature has provided humans with a built-in filter system (the hairs in nostrils) which will stop some dust particles; however, unless you were to live in a vacuum jar you can expect to be breathing dust continually. How you try to eliminate this ‘dust’ may make a great difference in your health. Problems can arise with the most common method of trying to remove dust, portable vacuum cleaners. An aspect from a German student’s doctoral thesis was published in Frankfurter Rundschau on March 12, 1979. The title above the exerpt read ‘Many vacuum cleaners (portable) are bacteria slingshots.’ She states ‘Bacteria flies through the pores of a vacuum cleaners’ paper bag like house flies fly through a fence.’ This bacteria stays suspended in the air for hours where it is easily inhaled by the occupants of the house. Her advice is to use the portable vacuum cleaner as little as possible and when you do to open the windows wide. The Franklin Journal picked up on this study and revealed a similar article shortly thereafter. In December of 1979, Consumer’s union also made mention of the study. In October of 1980, a program ran on Channel 13 in Clearwater, Florida about a scientist who had been ignored by the federal government for years; but, was beginning to get people to listen. He claims there is more danger from cancer in the home due to portable vacuum cleaners than there is in any manufacturing plant. He claims the only way to clean is with a central vacuum. Probably the best known report on this subject is book entitled, ‘Why Your House May Endanger Your Health’, (Simon And Shuster, $10.95) written by Dr. Alfred V. Zamm and Robert Gannon. Dr. Zamm is a dermatologist and an allergist who gives an indepth study of the possible problem areas in homes. Dr Zamm has been on TV (Donahue and PM Magazine) promoting his book. Local news shows and newspaper articles like the one which appeared in the January 25, 1981 Milwaukee Journal, have made mention of his findings. He devotes one whole chapter (15 pages) to ‘housedust’ and its effects. According to one study the average six-room home in a city or suburb accumulates around forty pounds of dust a year. Dr. Zamm and other physicians view ‘housedust’ as an ‘occupational hazard’ for the housewife because she breathes the dust, stirred up by cleaning, most of the day. Plain dirt tracked in from the outside is not that unhealthy; however, pet dander, mold spores, and housedust mites are. Housedust mites are small insects found in 2/3 of the households east of the Mississippi according to one study.

    Dr. Zamm devotes another chapter to maintaining a healthy house. In this chapter he discusses vacuuming with portables. He suggests to open the windows when cleaning, especially when using portable vacuums. Here is what Dr. Zamm says about vacuum cleaners. ‘Vacuum cleaners present a peculiar problem. They are by far the most effective device for removing dust, and yet most of them pollute more than they clean; they suck in dust from surfaces, then blow the smaller particles through the filter or bag into the air, particles that, because of their very small size, may slide through the body’s filtering mechanisms to lodge deep into the lungs. The best vacuum system is one built into the house, a system that pulls dust into a central unit, then blows it outside.’ Dr. Zamm also suggests ‘specialized equipment if prescribed by your allergist, may be used as a medical tax deduction’.