Concept
Elevator air conditioning is fast becoming a popular concept around the world. The primary reason for installing an elevator air conditioner is the comfort that it provides while travelling in the elevator. It stabilizes the condition of the air inside the lift car. Some elevator air conditioners can be used in countries with cold climates if a thermostat is used to reverse the refrigeration cycle to warm the lift car.
Health
One of the many benefits of installing an elevator air conditioner is the clean air that it provides.
Air is sucked from the elevator’s hoist way straight into the car using a motorised fan. The air sucked into the hoist way may be filled with dust mites, germs and bacteria.
With an elevator air conditioner, air provided is much cleaner because the cold air is the same air that comes from the car itself. Not only that, the cold air that is produced from the air conditioner also goes through a layer of filter. This filtration removes particles that are harmful to the human body.
A poorly maintained air-conditioning system may promote the growth and spread of microorganisms, but as long as the air conditioner is kept clean these health hazards can be avoided.
Energy
Elevator lobby air conditioning constantly leaks into the elevator shaft due to elevator movements and elevator shaft ventilation requirements, resulting in wasted energy. By using elevator air conditioners, less energy is used because the air conditioner is able to cool the inside of the elevator more effectively.
Drawbacks
Heat generated from the cooling process is rejected into the hoistway. The elevator cab (or car) is not air-tight, and some of this heat will reenter the car and reduce the overall cooling effect, which may be less than ideal.
Condensation
Air conditioning poses a problem to elevators because of the condensation that occurs. The condensed water produced has to be disposed of; otherwise, it would create flooding in the elevator car and hoistway.
Ways to remove condensed water
There are at least four ways to remove condensed water from the air conditioner. However, each solution has its pros and cons.
Atomizing
Atomizing, also known as misting the condensed water, is another way to dispose of the condensed water. Spraying ultra fine water droplets on to the hot coils of the air conditioner would ensure the condensed water evaporates quickly.
Though this is one of the best methods to dispose of the condensed water, it is also one of the costliest because the nozzle that atomizes the water easily gets choked. The majority of the cost goes to maintaining the entire atomizing system.
Boiling
Disposing of condensed water works by firstly collecting the condensed water and then heating it to above boiling point. The condensed water would eventually be evaporated thereby disposing it.
Consumers are reluctant to employ this system because of the high rate of energy used just to dispose of this water.
Cascading
The cascading method works by flowing the condensed water directly onto the hot coils of the air conditioner. This would eventually evaporate the condensed water.
The downside of this technology is that the coils have to be at extremely high temperature for the condensed water to be evaporated. There is a chance that the water might not evaporate entirely and that would cause water to overflow on to the exterior of the car.
Drainage system
Drainage system works by creating a sump to collect the condensed water and using a pump to dispose it off through using a drainage system.
It is an efficient method, but it comes at a heavy price because the cost of building the sump, and maintaining the pump to make sure it operates, is very expensive. Moreover, the pipes used for drainage would look ugly on the exterior. This system also cannot be implemented on a built project.
Controlling elevators
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General controls
A typical modern passenger elevator will have:
- Space to stand in, guardrails, seating cushion (luxury)
- Electric fans or air conditioning units to enhance circulation and comfort.
- Call buttons to choose a floor. Some of these may be key switches (to control access). In some elevators, certain floors are inaccessible unless one swipes a security card or enters a passcode (or both). In the United States and other countries, call button text and icons are raised to allow blind users to operate the elevator; many have Braille text besides.
- A set of doors kept locked on each floor to prevent unintentional access into the elevator shaft by the unsuspecting individual. The door is unlocked and opened by a machine sitting on the roof of the car, which also drives the doors that travel with the car. Door controls are provided to close immediately or reopen the doors. Objects in the path of the moving doors will either be detected by sensors or physically activate a switch that reopens the doors. Otherwise, the doors will close after a preset time.
- A stop switch (not allowed under British regulations) to halt the elevator while in motion and often used to hold an elevator open while freight is loaded. Keeping an elevator stopped for too long may trigger an alarm. Unless local codes require otherwise, this will most likely be a key switch.
- An alarm button or switch, which passengers can use to signal that they have been trapped in the elevator.
Some elevators may have one or more of the following:
- An elevator telephone, which can be used (in addition to the alarm) by a trapped passenger to call for help.
- Hold button: This button delays the door closing timer, useful for loading freight and hospital beds.
- Call cancellation: A destination floor may be deselected by double clicking.
- Access restriction by key switches, RFID reader, code keypad, hotel room card, etc..
- One or more additional sets of doors that can serve different floor plans. For example, in an elevated crosswalk setup, the front doors may open on the street level, and the rear doors open on the crosswalk level.
- Security camera
- Plain walls or mirrored walls giving the illusion of larger area
- Glass windowpane providing a view of the building interior or onto the streets.
Other controls, which are generally inaccessible to the public (either because they are key switches, or because they are kept behind a locked panel), include:
- Fireman's service, phase II key switch
- Switch to enable or disable the elevator.
- An inspector's switch, which places the elevator in inspection mode (this may be situated on top of the elevator)
- Manual up/down controls for elevator technicians, to be used in inspection mode, for example.
- An independent service/exclusive mode will prevent the car from answering to hall calls and only arrive at floors selected via the panel. The door should stay open while parked on a floor. This mode may be used for temporarily transporting goods.
- Attendant service mode.
Controls in early elevators
- Some older freight elevators are controlled by switches operated by pulling on adjacent ropes. Safety interlocks ensure that the inner and outer doors are closed before the elevator is allowed to move.
- Early elevators had no automatic landing positioning. Elevators were operated by elevator operators using a motor controller. The controller was contained within a cylindrical container about the size and shape of a cake container and this was operated via a projecting handle. This allowed some control over the energy supplied to the motor (located at the top of the elevator shaft or beside the bottom of the elevator shaft) and so enabled the elevator to be accurately positioned — if the operator was sufficiently skilled. More typically the operator would have to "jog" the control to get the elevator reasonably close to the landing point and then direct the outgoing and incoming passengers to "watch the step". After stopping at the landing the operator would open the door/doors. Some slightly later lifts though, had door(s) that could be operated by the same control (so when the lever is moved in the desired direction, between the idle and motion points there is a trigger to close the doors. When the handle is moved to idle, the doors open again.) This sort of arrangement was used sometimes in subway stations. Manually operated elevators were generally refitted or the cabs replaced by automatic equipment by the 1950s. The major exception is freight elevators which today are just as commonly operated manually as automatically, and even when equipped with automatic controls, are often operated by an attendant to ensure efficiency.
- Early automatic elevators used relays as logic gates to control them, which began to be replaced by microprocessors in the late 1980s.
- Large buildings with multiple elevators of this type would also have an elevator dispatcher stationed in the lobby to direct passengers and to signal the operator to leave with the use of a mechanical "cricket" noisemaker.
- Some elevators still in operation have pushbutton manual controls.
External controls
Elevators are typically controlled from the outside by up and down buttons at each stop. When pressed at a certain floor, the elevator arrives to pick up more passengers. If the particular elevator is currently serving traffic in a certain direction, it will only answer hall calls in the same direction unless there are no more calls beyond that floor.
In a group of two or more elevators, the call buttons may be linked to a central dispatch computer, such that they illuminate and cancel together. This is done to ensure that only one car is called at one time.
Key switches may be installed on the ground floor so that the elevator can be remotely switched on or off from the outside.
In sky lobby elevator systems, one would select the intended destination floor (in lieu of pressing "up") and be notified which elevator is to serve that request.
Floor numbering
The elevator algorithm
The elevator algorithm, a simple algorithm by which a single elevator can decide where to stop, is summarized as follows:
- Continue traveling in the same direction while there are remaining requests in that same direction.
- If there are no further requests in that direction, then stop and become idle, or change direction if there are requests in the opposite direction.
The elevator algorithm has found an application in computer operating systems as an algorithm for scheduling hard disk requests. Modern elevators use more complex heuristic algorithms to decide which request to service next.
Destination Control System
Some skyscraper buildings feature a destination operating panel where a passenger would register their floor calls before entering the car. The system would let them know which car to wait for, instead of everyone boarding the next car. In this way, travel time is reduced as the elevator makes fewer stops for individual passengers, and the computer distributes adjacent stops to different cars in the bank.
It can also improve accessibility, as a mobility-impaired passenger can move to his or her designated car in advance.
Inside the elevator there is no call button to push, or the buttons are there but they cannot be pushed – they only indicate stopping floors.
The system was first pioneered by Schindler Elevator as the Miconic 10. Manufacturers of such systems claim that average traveling time can be reduced by up to 30%.[10]
There are some problems with the system, though, and it is subject to gaming. Sometimes, one person enters the destination for a large group of people going to the same floor. The dispatching algorithm is usually unable to completely cater for the variation, and late comers may find the elevator they are assigned to is already full. Also, occasionally, one person may press the floor multiple times. This is common with up/down buttons when people believe this to be an effective way to hurry elevators. However, this will make the computer think multiple people are waiting and will allocate empty cars to serve this one person.
The same destination scheduling concept can also be applied to public transit such as in group rapid transit.
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