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Machine-Room-Less (MRL) Elevators
By Mike Ford
The elevator industry is offering a relatively new elevator product termed Machine Room-Less Elevators (MRL’s). Application in new construction or major renovation projects compared to standard elevator equipment is a fairly significant decision as it will affect the design of the elevator hoistways and equipment rooms. This article is written to explain the product history, benefits and limitations.
The machine-room-less elevator is the result of technological advancements that often allow a significant reduction in the size of the electric motors used with traction equipment. These newly designed permanent magnet motors (PMM) allow the manufacturers to locate the machines in the hoistway overhead, thus eliminating the need for a machine room over the hoistway. This design has been utilized outside the USA for at least 15 years and is becoming the standard product for low to low-mid rise buildings. It was first introduced to the U.S. market by KONE. Product acceptance was initially slow in the U.S. market because of its initial, limited applications, its inability to meet U.S. code requirements, and the limited number of manufacturers offering an equivalent product.
In the past three years the elevator manufacturers have overcome the obstacles to acceptance of the MRL product. All of the other elevator manufacturers are now marketing their versions of the MRL, and the product offering has been expanded to include many of the more popular elevator sizes and speeds. In addition, local code officials have become more receptive to the technology; most are now allowing the equipment to be installed in their respective jurisdictional areas, at least on a case by case basis.
Benefits of the MRL Elevator
• The use of the MRL elevator will save a significant amount of energy (estimated at 70-80%) as compared to hydraulic elevators. The power feeders for the MRL are also significantly reduced due to the more efficient design and the counter-balancing provided with traction equipment.
• The MRL elevator eliminates the cost and environmental concerns associated with a buried hydraulic cylinder filled with hydraulic oil. Over the years hydraulic elevators have come under greater scrutiny relative to environmental concerns due to the buried hydraulic cylinder. Because the MRL elevator is a traction elevator with all its components above ground, this is not a concern for this equipment.
• The MRL elevator utilizes a gearless traction type machine, which results in superior performance and ride quality compared with hydraulic elevators. MRL’s can also operate at faster speeds thus increasing the perception of quality over a conventional hydraulic elevator.
Concerns with the MRL Elevator
• MRL are still relatively new to the United States. Our firm is reluctant to promote products that do not have solid and proven track records of reliability. We go to great lengths to validate manufacturer’s claims and performance records. One manufacturer has recently removed their MRL product from the market and is attempting to redesign and introduce a new offering.
• ASME A17.1 code does not specifically address the MRL design. It is just a matter of time until new code verbiage is added to accommodate the MRL. In the meantime, most states and code enforcing authorities are allowing the product installation under a project specific variance.
• Until the very recent past the MRL elevator products did not offer an economical advantage over traditional elevator products. The market is now experiencing certain MRL elevators priced more competitively, comparable to a traditional geared traction elevator. Certain manufacturers have tried to introduce a cost competitive product to compete with the low rise hydraulic elevator. One manufacturer is being somewhat successful; another has discontinued their low rise MRL product offering.
• Each manufacturer has engineered their product with limitations that allow them to utilize the small gearless machine and their means of cab suspension. The capacity, speed and cab interior limitations, especially with larger service type elevators, have restricted the product in various applications.
Based on our firm’s experience with each product application, its reliability and serviceability, Lerch, Bates & Associates currently approves the use of the Otis Elevator Company MRL elevator (Gen2) and the KONE Incorporated MRL elevator (MonoSpace/EcoSpace) in certain applications. It has been our experience other MRL elevator products have intermittent issues; however, we anticipate these concerns to be addressed in time.
It also should be emphasized that the critical building requirements vary significantly to accommodate different manufacturers’ MRL elevator product. This is due to different methods of cab suspension, and locations of the machine, controls and counterweight.
In general, the MRL elevator product still requires the original equipment manufacturer to maintain the product after turnover. Consequently, Lerch, Bates & Associates urges our clients to secure long term maintenance pricing when soliciting new equipment bids. This method of procurement will ensure a competitively priced maintenance program, as well as allow for a beneficial life cycle cost comparison to other more traditional elevator products.