Shunt trip elevator concerns:
In your more modern high-rise buildings protected by automatic sprinklers, codes require that the elevator shaft and elevator machinery room be protected by a sprinkler system. Prior to the installation of a shunt trip breaker, any water discharged from a sprinkler in the elevator hoist way or machinery room could cause the elevator to malfunction allowing the elevator car to run with the car doors open, run past selected floors, stop in between floors, crash into the elevator pit and even possibly energize the elevator car itself and present a danger from electrocution. To prevent this from occurring, codes require smoke/heat detectors to be installed in the hoist way and machinery room near the sprinkler heads. In the event the detector senses smoke/heat prior to the activation of the sprinkler head, or if the systems detects water flow from a discharged head, a signal is sent to the “shunt trip” breaker installed in the circuit feeding the elevator controls.
If the shunt trip breaker activates, it is designed to remove power from the elevator car. This will stop the elevator car regardless of where it is in the shaft trapping anyone in the car. Although the shunt trip design has been installed to protect those within the car, it can also trap people and even firefighters in a Phase 2 elevator operation causing another concern to deal with at a high-rise fire.
If a smoke is present in the elevator shaft or machinery room, the smoke detector will activate a circuit in the elevator controller and send a warning directly to the car. The warning will be the flashing red firefighter helmet/light on the control panel within the car. This indicates that smoke and fire are near the elevator machine room or hoist way and that a power shunt trip is possible. If you see the flashing red fire helmet, it is recommended that you do NOT use the elevator, you will probably get stuck! If you are in the elevator car and moving and the firefighter light begins to flash, immediately hit the call cancel button, select the next/closest floor and exit the elevator.
This feature is in all elevators installed since 2004 with sprinkler systems in elevator hoist way and machinery rooms. A power shunt trip has to be manually reset from the elevator machinery room.
As a reminder at all high-rise operations, prior to entering the car, obtain information from the alarm panel on the fire or smokes location. Alarm information regarding a sprinkler, heat or smoke detector activation in the elevator machinery room or elevator hoist way that services a specific bank of elevators will prevent you from entering into an elevator car and getting stuck. Shy of definitive alarm information, pay attention to the elevator control panel within the car. If the firefighter helmet light starts flashing, get out of the car!
Stay Safe!
Mike Terpak
Deputy Chief-Jersey City
