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Tuesday, March 24, 2015

Elevator Shunt Trip with Sprinkler Heads

What is Elevator Shunt Trip?


Elevator shunt trip wiring deta
Elevator Shunt Trip Wiring Detail
Elevator controls play a huge role in fire alarm system emergency functions. Whereas elevator recall captures and sends the elevator cab to safe floors, shunt trip works a little different.  Elevator Shunt Trip is a function that involves shunting the breaker that controls the elevator equipment prior to the release of the automatic sprinkler systems.  This procedure is completed via the activation of heat detectors (addressable or conventional).  Now keep in mind that not just any heat detector within the facility will be required to activate the elevator shunt trip procedure.  The only heat detectors that will tell the fire alarm control panel to shunt the elevator breaker are the ones located in the elevator shaft or hoistway and elevator equipment room.  Per NFPA 72 2013 edition section 21.4.2* the heat detectors that are in place to shunt the elevator power shall be installed within 24" of each sprinkler head within the area.  On top of this section 21.4.1* states the heat detector used for shunt trip shall be set at a lower temperature and higher sensitivity than its adjacent sprinkler head.

One last thing, the activation of heat detectors can delay the shunt trip via programming for a delay time not to exceed the time it takes the elevator cab starting at the top level to reach the lowest level of exit discharge.  The purpose behind this allowance is to increase the potential for elevators to complete their travel to the recall level.  Make note that the requirements of A17.1/B44 Safety Code for Elevators and Escalators would still apply.

Now if you choose to use the method of waterflow or pressure switch to activate you elevator shunt trip, any time delay switches or capability will not be permitted per NFPA 72 2013 section 21.4.3.
video


When the shunt trip breaker is activated, the breaker switch itself will be between on and off.  To reset the breaker, make sure the controlling fire alarm system is reset and back to normal.  Once the FACP is reset, flip the shunt trip breaker all the way towards the off position (should be some tension) and then flick it all the way back to on.  Review the short video for more details on resetting a shunt trip breaker.

Code References for Elevator Shunt Trip:


ASME A17.1-2004

2.8.2.3.2 In jurisdiction not enforcing the NBCC, means shall be provided to automatically disconnect the main line power supply to the affected elevator upon or prior to the application odf water from sprinklers located in the machine room or in the hoistway more than 600 mm (24") above the pit floor.  This means shall be independent of the elevator control and shall not be self-resetting.  The activation of sprinklers outside of the hoistway or machine room shall not disconnect the main line power supply.

ASME A17.1-2013

2.8.3.3.2 In jurisdictions not enforcing the NBCC, where elevator equipment is located or its enclosure is configured such that the application of water from sprinklers could cause unsafe elevator operation, means shall be provided to automatically disconnect the main line power supply to the affected elevator and any other power supplies used to move the elevator upon or prior to the application of water. (a) This means shall be independent of the  elevator control and shall not be self-resetting.

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