Central vacuum cleaner
A central vacuum cleaner 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 made a central vacuum system more affordable and popular in North America, by using PVC extruded pipe instead of metal tubing for the piping system inside the walls. Previously, more expensive metal tubing was used exclusively. Central vacuum systems also started to become popular among European consumers interested in their hygienic and convenience benefits.
By the 1990s, central vacuum systems gained popularity among real estate agents and home remodelers for the value they added to homes at resale. Allergists also played an important role in the growing popularity of central vacuum systems in the 1990s.
Power
The suction power of a vacuum cleaner is calculated in airwatts —not to be confused with watts, which only refers to electrical power. 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. The air watts indicate the motor's global performance, and thus the central vacuum's efficiency level.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. 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. Water lift measures the maximum suction force 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.
If two motorized blowers are set up in parallel, both motors work independently. Each of them takes its airflow from the same canister but has its own air inlet and air outlet. This configuration generates more airflow volume. Airflow indicates the amount of air vacuumed per minute or per hour with a fully opened hose. The higher the value, the greater the cleaning area that is covered by the inlet. A bigger airflow is preferable to clean hard-surfaced floors to reach dust as far as possible. Higher airflow is also desirable if multiple inlets are likely to be used at the same time.
Operation
To use a central vacuum, the vacuum hose is removed from storage and fitted with any needed cleaning accessories. 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. 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. 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. For a more complete technical description of this process, see the article on "Cyclonic separation".
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 or replaced 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.
Bag breakage is an issue that arises with filtered central vacuums. In a portable vacuum, if the filter bag fails, this condition becomes immediately obvious as a cloud of dust and dirt blows into the room. Although it creates a mess, at least the problem can be immediately brought under control by shutting off the appliance. By contrast, if the filter bag in a central unit should fail, little change may be noticed by the remote operator. The only perceivable change may be an increase in suction power as a clogged but broken bag is completely bypassed. If the filtered air is also used to cool the motor, the first clue that something is amiss may be when the motor completely seizes up due to dirt accumulating in the motor brushes, windings, or bearings. Such a failure can require a complete replacement of the expensive central unit.
Filterless central vacuums are completely immune to such failures. 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 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.The average standard central vacuum system is equipped with a 30 foot hose, plus standard cleaning tools similar to those used with portable vacuum cleaners. For further convenience, some owners will keep a hose and set of tools on each floor of a multi-story building. When not in use, the hose is loosely coiled around a wire rack mounted on a closet wall, or on the back of a door.
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. Successful installation of such systems requires special fittings, and careful design and workmanship, to ensure smooth hose retraction into the piping for storage. A scaled-down 10-foot version is available for quick cleaning in locations such as mud rooms and laundry rooms. The original "Vroom" system, which is still available, uses suction to operate a cabinet-mounted hose reel with a 24 ft hose, rather than storing the hose within the wall piping.
A modular vacuum hose called "QuickClick" is available in 10/15/20 foot lengths, allowing a custom-length hose to be quickly set up or taken apart by an end user. In addition, a promotional article in a trade magazine says that arthritic testers were able to connect and disconnect the hose despite their disability.
Automatic dustpans can be installed in the kickspace under a kitchen, bathroom, or workroom countertop, enabling a person to use a standard broom to sweep debris directly into a vacuum inlet located there. Alternatively, a "DrawerVac" inlet which pulls out like a drawer from the underside of a table or counter can be used to dispose of debris from a shop or kitchen work surface.
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, which is said by the manufacturer to preserve food freshness for a longer period.