A central vacuum cleaner (also known as built-in or ducted) is a type of vacuum cleaner appliance installed into a building as a semi-permanent fixture. Central vacuum systems are designed to remove dirt and debris from homes and buildings by sending dirt particles through piping installed inside the walls to a collection container inside a remote utility space. The power unit is a permanent fixture, usually installed in a basement, garage, or storage room, along with the collection container. Inlets are installed in walls throughout the building that attach to power hoses and other central vacuum accessories to remove dust, particles, and small debris from interior rooms. Most power hoses have a power switch located on the handle.
History
19th century Early steam-powered vacuum cleaners were mounted in a heavy carriage equipped with a long hose so they could be moved from one location to another, providing a specialized cleaning service by appointment. Stationary-powered vacuum cleaners were built-in and centralized, due to the large and heavy machinery needed to produce the required airflow. Their high cost restricted their installation to commercial and industrial locations.
The first introduction of a permanent system similar to a residential central vacuum cleaner was in the late 19th century. A ducted machine featuring copper tubes connected from a bellows chamber, typically located in the basement and extended to several locations throughout a building, was used in a select few homes. Because of the machine's cost and weak dust-removal capabilities, only a few units were ever sold in the United States.
In 1869, Ives McGaffey patented the first portable vacuum cleaner, or sweeping machine. Steam power was replaced by electric motors, which were still too large and heavy for portable use, but gradually became smaller and more powerful.
20th century
By the 1930s, the development of small, powerful electric motors increased the popularity and availability of the portable vacuum cleaner, and diverted consumers from purchasing central cleaners.
By the early 1960s, the introduction of polyvinyl chloride (PVC) made a central vacuum system more affordable and popular in North America (especially Canada), by using PVC extruded pipe instead of metal tubing for the piping system inside the walls. Previously, more expensive metal tubing was used exclusively (and it may still be used for part or all of an installation, if required by building fire code regulations).
Power The suction power of a vacuum cleaner is measured in airwatts (or air watts). This is not to be confused with motor input power in watts. The airwatt value relates to the airflow, the water lift, and power consumption. This datum is calculated as follows: P = 1/8.5 x F x S where P translates to the power in air watts; F is the airflow in CFM; and S for the water lift in inches. The standard air watt formula is from ASTM International (see document ASTM F558-21).
Nowadays, the power of single-motor central vacuums is usually between 500 and 800 airwatts. For central vacuums that operate with two motors, the best practice for representing the vacuum cleaner power is to prefix "2 X" in front of the power for one motor. For instance, if a central vacuum has two motors with a power of 500 airwatts each, the whole central vacuum has 2 X 500 airwatts. Airwatts cannot be added together; a unit with two motors of 500 airwatts each does not make a 1000-airwatt unit.
For central vacuums with two motors, the airflow may be connected in series or in parallel (not to be confused with the electrical connections, which are always in parallel). When two motorized blowers are connected in series, both motors work together so that the air outlet of the first one is the air inlet of the second one. This configuration gives more water lift (measured in inches or millimeters). Water lift measures the maximum suction force ("pressure") of the device when the hose opening is blocked. The higher the value, the heavier the objects or dense materials which can be easily vacuumed. A high suction force is usually required for deep carpet cleaning or vacuuming liquids.
Operation
To use a central vacuum, the vacuum hose is removed from storage and fitted with any needed cleaning accessories (such as a brush). The other end of the hose is inserted into a wall-mounted vacuum inlet, after opening the spring-loaded cover door. In some designs, opening the door switches on the vacuum motor; in other designs, insertion of the metallic hose-end fitting bridges two electrical contacts, signalling the motor to turn on. Other alternative designs feature a remote on/off switch located at the tool end of the vacuum hose, which communicates either via a pair of wires embedded in the hose or via wireless signalling.
Vacuuming is performed in the same manner as with a portable machine. Sometimes, the higher suction power of the central vacuum may require reduction (for example, when cleaning a delicate sheer fabric curtain). Excess suction is "bled off" by partially opening a bleed port or slot to let some intake air bypass the cleaning tool. The bleed port is usually located at the tool end of the vacuum hose, to allow quick adjustment during use.
When cleaning is complete, the vacuum hose is removed from the wall inlet (which snaps shut and shuts down the vacuum motor). The hose is coiled up and hung on a storage rack, and any cleaning accessories are stowed away.
Dirt separation Cyclonic and filtered central vacuum systems are the two main types of central vacuums, differentiated by the method used to separate dirt and dust from the incoming airstream.
True cyclonic cleaners do not use filtration bags, instead separating the dirt and dust into a detachable cylindrical collection vessel or bin. Air and dust are sucked at high speed into the collection vessel at a direction tangential to the vessel wall, creating a fast-spinning vortex. Roughly speaking, the dust particles and other debris spiral outward to the wall of the vessel by centrifugal force, where they fall due to gravity into the bottom of the collection bin.
In fixed-installation central vacuum cleaners, the cleaned air may be exhausted directly outside without the need for further filtration. A well-designed cyclonic separation system does not lose suction power due to airflow restriction until the collection vessel is almost full. This is in marked contrast to filter bag systems, which gradually lose suction as pores in the filter become clogged by collected dirt and dust.
Filtered systems use a wide variety of different bags or filters that must be cleaned (permanent cloth bags) or replaced (disposable paper bags) regularly. Filters can be made from screening, foam, paper, or cloth, and are usually proprietary designs that may not be widely available. Over time, repeated purchases of filters and bags can become significant ongoing expenses.
Motors of both filtered and filterless systems are usually protected by a thermal cutoff switch, which disconnects the power if the motor overheats due to blocked airflow. In addition, the best designs in either system incorporate so-called "bypass cooling", using a completely separate source of ambient air to cool the motor, rather than the cost-saving expedient of using the just-filtered dirty airflow for this vital function.
Hybrid cyclonic filtered systems have been made, which use a rudimentary cyclonic motion to separate larger dirt particles but rely on conventional filter bags to trap the remaining finer particles. True cyclonic systems are very effective in removing all but the finest particles, which are then exhausted directly outside, eliminating the need for replaceable filters and their consequent airflow restrictions. The exhaust from a good quality true cyclonic system does not contain any visible large particles, and contains far less debris than a typical clothes dryer exhaust.
Tools and accessories
Central vacuums can be equipped with either an electrical power brush or an air-driven power brush. The air-driven (or turbine) systems are frequently less expensive since they do not require electrical wires for power to be run to each wall inlet. Turbine-driven brushes tend to be louder than electric brushes; the noise from either is more noticeable in the absence of the "vacuum whine" produced by a portable vacuum. Many users find that the high suction of central vacuums is more than sufficient by itself for most casual cleaning jobs, but reserve a powered brush tool for more difficult tasks.
An alternative for storing vacuum hoses is the "Hide-A-Hose" system, which uses suction to draw the hose into the vacuum piping in the wall for storage. Hose lengths used are typically 30/40/50 ft (9/12/15 m). Successful installation of such systems requires special fittings, and careful design and workmanship, to ensure smooth hose retraction into the piping for storage.
Automatic dustpans (e.g. "Vacpan" or "KickSweep") can be installed in the kick space beneath a kitchen, bathroom, or workroom countertop, enabling a person to use a standard broom to sweep debris directly into a vacuum inlet located there.
The "VacnSeal" is an accessory intended to be installed on the underside of a kitchen cabinet, over a countertop used for food preparation. The nozzle of the device is used to evacuate excess air from a zipper lock plastic food storage bag (e.g. Ziploc), which is said by the manufacturer to preserve food freshness for a longer period.
Advantages
Increased suction power — Because the vacuum cleaner motor and dirt collection system need not be portable, the weight and size of the unit are not as severely limited compared to a portable system; some units even use two motors for extra power. In addition, bagless filterless systems avoid the inevitable loss of suction in filtered systems caused by collected dust clogging the filters. Complete removal of allergens and noxious odors — Central vacuums generally do not recirculate exhaust air back into the space being cleaned. This contrasts with the well-known acrid "vacuum smell" of fine dust and hot air exhausted from a portable vacuum. Instead, central vacuums exhaust spent air into a utility space, or directly outdoors. An external exhaust outlet can be easily concealed under a porch or behind shrubbery, but in any case, is less obtrusive than a standard clothes dryer appliance vent. Central vacuum installations can earn points for Leadership in Energy and Environmental Design (LEED) home certification, Health House certification by the American Lung Association, or the National Green Building Standard of the National Association of Homebuilders (NAHB). Health benefits – A study conducted in 2001 at the University of California at Davis showed improvements in multiple aspects of health in 25 individuals with a documented history of type I hypersensitivity to house dust. Each of these individuals used either a Beam Central Vacuum System or their conventional vacuum for three months. At the end of this period, the individual switched over to the opposite limb of the study for three additional months. The results showed that using a central vacuum system was superior in seven domains of evaluation, including activity, sleep, non-nasal symptoms, practical problems, nasal symptoms, eye symptoms, and emotions. Low acoustic noise — Well-designed central vacuums are very quiet at the point of use since the powerful motor is located remotely in a utility space. This is a benefit to the person vacuuming, as well as anybody else occupying the space being cleaned, who otherwise might be woken up or driven out by the loud whine of a portable machine.