Mersen’s Fusible Shunt Trip Switch offers remote load-break capability and fuse protection for elevator circuits

April 19, 2017
Mersen’s Fusible Shunt Trip Switch is an all-in-one solution that meets required codes for safety in elevator shafts.

Mersen’s Fusible Shunt Trip Switch is an all-in-one solution that meets required codes for safety in elevator shafts. This UL-Listed control panel offers remote load-break capability and fuse protection for elevator circuits. An array of available options allows for maximum functionality to be built into a single compact panel.

There are several codes and standards relating to elevator circuits:

NFPA 13, 8.14.5 and ANSI/ASME A17.1: According to NFPA 13, 8.14.5, sprinkler protection isrequired at the top and bottom of elevator shafts. With that being said,NFPA 13 requires the installation of sprinklers in the elevator machineroom. Once a sprinkler system has been introduced to either the elevatorshaft or elevator machine room, you are now installing these per theState-Adopted Elevator Code ANSI/ASME A17.1. To summarize ASME A17.1, Safety Code for Elevators and Escalators, Rule102.2 (c) (3) requires the shutdown of power to the elevator prior to theapplication of water in the elevator machine room and or hoistway. The shutdown of power is accomplished by a shunt trip device in theelevator circuit. This reduces the risk of any potential electrical shockonce the water is released into the system. This will also reduce the riskof any elevator car slippage once the cables and hoist system becomesaturated from the release of water.

NFPA 72 In addition to turning off the power,2002 NFPA 72 (Fire Alarm Code) requires “Control circuits to shut down elevator power shall be monitored for thepresence of operating voltage. Loss of voltage to the control circuit forthe disconnecting means shall cause a supervisory signal to be indicatedat the control unit and required remote annunciation.” This is achieved with the Fire Monitoring Relay (FR Relay), a standardfeature in Mersen’s Fusible Shunt Trip Device.

NEC 620.91: In the event of a power loss, at which point a back-up power supply isintroduced to the system, you are now required to meet NEC Article620.91 paragraph (C) emergency or standby power system. This isaccomplished with a set of mechanical interlock auxiliary contacts whichcomes standard as 1-N/O and 1-N/C contact. The auxiliary contactsprevent the elevator from descending down and injuring any workersthat could be working in the elevator shaft. This also allows the elevatorto move to the next convenient location and open the doors to let anypassengers out in the event of an emergency.

Fusible shunt trip disconnect switches are a required safety feature in many industrial and commercial applications. Main branch-circuit fuses provide overcurrent protection in the event of short circuits, power surges, damage to electrical wiring, etc. by interrupting faulty circuitry and removing it from the electrical system. In addition, the molded case switch can disconnect power from the source prior to known electrical disturbances, before the fuse is required to operate. Integrated into the molded case switch is an electromagnet (shunt trip coil), controlling a spring-loaded conductive strip which maintains continuity between the line side and load side terminals of the switch. The electromagnetic coil is normally connected to a safety system, such as a fire alarm or smoke detector housed in the surrounding building. Should there be an electrical emergency, a signal is sent to the coil (via the safety system, alarm, sprinkler, etc.) and the electromagnet would be engaged, throwing the switch and disconnecting power. Power can only then be reenergized by manually operating the molded case switch.