MRL Elevator: KONE EcoDisc History, Overhead Machine Position, EN 81-20 Access Requirements and Energy Efficiency

Machine Room-Less (MRL) elevators represent the most significant innovation in elevator design since the introduction of the electric traction elevator. Development: KONE EcoDisc (1996) was the first commercial MRL using a flat permanent-magnet synchronous machine (PMSM); Otis Gen2 (2000) followed with flat-belt suspension instead of round ropes. Design approaches: (1) Overhead MRL — machine mounted on a bracket in the overhead structure (above the highest landing); control panel in a cabinet on the landing wall adjacent to the top landing; most common configuration; (2) Pit MRL — machine in pit; very rare; (3) Side-mounted machine — in the hoistway alongside the counterweight; used by some manufacturers. EN 81-20 compliance: EN 81-20:2014 was the first edition to fully codify MRL requirements, including: (a) access to the machine and governor must not require ladder work over the hoistway void; access routes must be safe; (b) emergency operation from outside the hoistway; (c) remote release of brake from landing; (d) levelling accuracy requirements unchanged. Advantages over machine-room elevators: no machine room required (saves 4–8 m² floor area); typically 20–30% lower installation cost; PMSM + VVVF drive achieves high energy efficiency; minimal lubrication. Limitations: higher maintenance access complexity; control panel in landing cabinet may be vandal risk; not suitable for very high-speed or very high-rise applications (>6 m/s, >60 floors).

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