Elevator shutdown, frequently referred to as shunt trip, is intended to immediately stop elevators before water from elevator machine room or hoistway sprinklers affects brakes and electrical equipment. Both wet brakes and wet electrical equipment can cause erratic life threatening elevator operation. Therefore, it is required by Requirement 126.96.36.199.2 of ASME A17.1 (Safety Code for Elevators, Escalators and Moving Walks) to "cause disconnection of the main line power supply upon or prior to the application of water from sprinklers in the machine room or hoistway". This occurs even if the elevator car is occupied and not at a landing. Oddly, this has the effect of potentially trapping occupants between floors in an elevator during a fire.k-911 said:Are shunt trip breakers required by code on all commercial elevators? My GC is installing a two floor commercial elevator, 240 volt single phase and said no shunt trip needed. I don't think so! Any thoughts!
Perhaps user SpeedyPetey will add additional comments, since he's a former big-city electrician and has probably wired up his share of elevators.VI. Disconnecting Means and Control
620.51 Disconnecting Means. A single means for disconnecting
all ungrounded main power supply conductors for
each unit shall be provided and be designed so that no pole
can be operated independently. Where multiple driving machines
are connected to a single elevator, escalator, moving
walk, or pumping unit, there shall be one disconnecting
means to disconnect the motor(s) and control valve operating
The disconnecting means for the main power supply
conductors shall not disconnect the branch circuit required
in 620.22, 620.23, and 620.24.
(A) Type. The disconnecting means shall be an enclosed
externally operable fused motor circuit switch or circuit
breaker capable of being locked in the open position. The
disconnecting means shall be a listed device.
FPN: For additional information, see ASME/ANSI A17.1-
2000, Safety Code for Elevators and Escalators.
Exception: Where an individual branch circuit supplies a
wheelchair lift, the disconnecting means required by
620.51(C)(4) shall be permitted to comply with 430.109(C).
This disconnecting means shall be listed and shall be capable
of being locked in the open position.
(B) Operation. No provision shall be made to open or
close this disconnecting means from any other part of the
premises. If sprinklers are installed in hoistways, machine
rooms, control rooms, machinery spaces, or control spaces,
the disconnecting means shall be permitted to automatically
open the power supply to the affected elevator(s) prior to
the application of water. No provision shall be made to
automatically close this disconnecting means. Power shall
only be restored by manual means.