D&D Elevator on Wednesday, July 8, 2020 at 12:00:00 am
Found these days in older residential buildings, Single-Speed AC (SSAC) electric traction elevators are now obsolete and are no longer made or installed. Current owners and managers of such properties who continue to operate these elevators are urged to seriously consider upgrading their equipment to modern standards, since continued operation of this outdated technology presents many potential hazards and problems best to avoid:
SSAC elevators first appeared during the post-World War II period, often installed as upgrades to earlier, prevalent DC systems as the municipal trolley grids that powered them became extinct, with installation continuing well into the 1970s. Popular at the time because they were attractively priced, they typically appeared in low- to mid-rise residential buildings, including condo conversions and rental apartments. These elevators are slow, low-capacity passenger units that are prone to intermittent leveling fluctuations. Since they rely on brakes to stop the car in properly level position – which often can be imprecise and inaccurate – they present trip-and-fall hazards, particularly to elderly passengers and those with mobility disabilities who may find it extremely difficult to negotiate level differences.
Conversely, today’s elevators have abandoned the use of brakes to stop the car, instead employing VVVF (Variable Voltage-Variable Frequency) control systems that consistently stop the elevator at floor level within tolerances of ¼-inch. As their name implies, these adjust both the voltage and frequency of the power applied to the hoist motor, thereby varying the speed at which the motor operates. With this technology, the hoist motor can be brought to a so-called “electrical stop” – with the hoist motor energized but not turning. This allows floor stops to be accurately specified, without regard to the load in the car.
Current New York State code requires that elevators, when arriving at a floor, stop accurately and consistently within a finite limit of ½-inch above or below floor level. This is reflected in the current edition of The American Harmonized Elevator code (CSA B44/ASME A17.1). The Technical Standards & Safety Authority (TSSA) has also written on the matter, recommending that these elevators, because of their poor leveling ability, should be upgraded.
D&D Can Help
The experts at D&D Elevator stand ready to help you evaluate your particular needs, to cost-efficiently achieve safety, code-compliance – and peace-of-mind!