Hydraulic elevators are supported by a piston at the bottom of the elevator that pushes the elevator up. They are used for low-rise applications of two to eight stories and travel at a maximum speed of 200ft/min. The machine room for hydraulic elevators is located at the lowest level adjacent to the elevator shaft.
Conventional Hydraulic Elevators have a sheave that extends below the floor of the elevator pit, which accepts the retracting piston as the elevator descends. Some configurations have a telescoping piston that collapses and requires a shallower hole below the pit. Max travel distance is approximately 60ft.
Hole-less Hydraulic Elevators have a piston on either side of the cab. In this configuration, the telescoping pistons are fixed at the base of the pit and do not require a sheave or hole below the pit. Telescoping pistons allow up to 50ft of travel distance. Non-telescoping pistons only allow about 20ft of travel distance.
Roped Hydraulic Elevators use a combination of ropes and a piston to move the elevator. Maximum travel distance is about 60ft.
Hydraulic elevators have a low initial cost and their ongoing maintenance costs are lower compared to the other elevator types. However, hydraulic elevators use more energy than other types of elevators.
Traction elevators are lifted by ropes, which pass over a wheel attached to an electric motor above the elevator shaft. They are used for mid and high-rise applications and have much higher travel speeds than hydraulic elevators. A counter weight makes the elevators more efficient.
Geared Traction Elevators have a gearbox that is attached to the motor, which drives the wheel that moves the ropes. Geared traction elevators are capable of travel speeds up to 500ft/min. The maximum travel distance for a geared traction elevator is around 250ft.
Gear-less Traction Elevators have the wheel attached directly to the motor. They are capable of speeds up to 2,000ft/min and have a maximum travel distance of around 2,000ft so the only choice for high-rise applications.
Geared traction elevators are middle of the road in terms of initial cost, ongoing maintenance costs, and energy consumption. Gear-less traction elevators have a high initial cost, medium ongoing maintenance costs, and use energy a bit more efficiently than geared traction elevators.
Machine-Room-Less (MRL) Elevators
Machine-Room-Less Elevators are traction elevators that do not have a dedicated machine room above the elevator shaft. The machine sits in the override space and is accessed from the top of the elevator cab when maintenance or repairs are required. The control boxes are located in a control room that is adjacent to the elevator shaft on the highest landing and within around 150ft of the machine.
Machine-room-less elevators have a maximum travel distance of up to 250ft and can travel at speeds up to 500 ft/min. MRL elevators are comparable to geared traction elevators in terms of initial and maintenance costs, but they have relatively low energy consumption compared to geared elevators.
Machine-room-less elevators are becoming the most popular choice for mid-rise buildings where the travel distance is up to 250ft. They are energy efficient, require less space, and their operation and reliability are on par with gear-less traction elevators.