Tuesday, December 20, 2016

Elevator Recall and Shunt Trip Basic

Here are the BASIC fundamentals of elevator recall and elevator shunt trip for fire alarm systems.

With elevator technology changing every year, it is affecting the requirements of the fire alarm system.  Even with the addition of elevator control rooms and elevator closets, most of the fire alarm elevator recall service remains the same. Below are some key points as well as code/standard references to assist you in understanding the basics of elevator recall and elevator shunt trip with fire alarm systems.
    Elevator shaft with fire alarm
  • 1st Floor Elevator Lobby Smoke Detector (activates alternate level recall sending the elevator to the second floor)  NFPA 72 2013 21.3.14.2
  • 2nd Floor Elevator Lobby Smoke Detector (activates designated level recall sending the elevator to the first floor)  NFPA 72 2013 21.3.14.1
  • Elevator equipment room Smoke (if its on the designated recall level, it should send the elevator to the alternate recall level, if the room is on the alternate recall level, the smoke should send the elevator to the designated recall level)
  • Elevator equipment room Heat (Only required if the room is covered by automatic sprinklers)  If this is the case, a heat detector shall be mounted within 2 feet of all sprinkler heads (NFPA 72 2013 Edition 21.4.2).  This heat detector will activate the elevator shunt trip function causing the elevator power to shut down.  Per NFPA 72 2013 the heat detector shall be set at both a higher sensitivity and lower temperature setting than the sprinkler heads.  This is so that the elevator power can be shut down before water is released on live (hot) equipment.  Note that a time delay must be in place to allow the elevator to travel from the top of the elevator hoistway to the lowest level of recall prior to shutting down the power (see NFPA 72 2013 Edition A21.4.2)
  • Elevator shaft or hoistway.  If the top of the elevator hoistway or shaft is equipped with an automatic sprinkler head, you are required to install a smoke detector and a heat detector within 2 feet.  The smoke detector will recall the elevator to the first floor and the heat detector will activate the shunt trip as stated above.  Note that a time delay must be in place to allow the elevator to travel from the top of the elevator hoistway to the lowest level of recall prior to shutting down the power (see NFPA 72 2013 Edition A21.4.2).  Also note that other methods can be used to achieve shunt trip function with elevators and fire alarm systems.  One way is to use a heat as specified above, two is to use a pre-action systems, and three is to use a waterflow/pressure switch.  If a waterflow or pressure switch is used for the shunt trip function of an elevator, there shall NOT be a delay (see NFPA 72 2013 Edition 21.3.3).  On top of that, the automatic sprinkler pipe branch has to be dedicated with its own ITV (inspectors test valve).  More information found here.
  • Elevator shaft or hoistway pit.  If there is an automatic sprinkler head located in the elevator pit remember this.  The head must be located higher than 2 feet off the bottom of the shaft in order to require any special requirements from the fire alarm system.  If the sprinkler head is located at 2 feet or lower, nothing is required on the fire alarm side.  Here is an article titled "Is a Heat Detector Required in the Elevator Pit".
  • Fireman's hat light.  You have probably seen it, it is a red light located at the elevator controls depicting the side profile of a fireman's hat.  This light needs to be programmed to activate (illuminate) if there is an activation of any fire alarm device in the elevator equipment room and or elevator shaft or hoistway.  This is in place to warn first responders that there is a fire in the elevator equipment room and or shaft so DO NOT OPEN!  See NFPA 72 2013 edition 21.3.14.3*
Now in today's world we have three different rooms we want to research before we layout the fire alarm devices required for a particular elevator recall system.  Below is a breakdown of these three rooms.
  • Elevator Machine/Equipment Room:  This is the standard room that we see on most projects. This room will house all of the actual elevator equipment, machines, motors, controls  etc.  In this room, we need to install the necessary relays for recall (primary and alternate as well as a relay for the fireman's hat light, smoke detection to cover the room space and heat detection if the area is is covered/protected by an automatic fire sprinkler system.
  • Elevator Control Room:  This is a smaller room that houses the controls for the elevators. This room will not contain the actual motors or machinery for the cars themselves.  The machinery and equipment will be located within the elevator shaft.  With that said, the
  • Elevator Closet:  This is a panel within the elevator shaft that houses all of the controls for the car's machinery.  Like the elevator control room, the closet is a clear indication that the machinery is located in the shaft.
Here is a sample elevator shunt trip wiring diagram article