Ups and Downs

Life Safety Systems July 2020

Two issues always seem to cause the most headaches when installing fire alarm systems. One has to do with duct detectors. The other has to do with installing fire alarm devices to interface with elevator controllers. There is a lot of confusion about the requirements, so I hope to clarify at least some of it here. I am basing my info on the 2019 NFPA 72. If you use an older version, it will still apply in most cases, but please do check your edition when installing the equipment.

First of all, it is important to remember that elevator inspectors use the elevator code, and fire inspectors use NFPA 72. The requirements for smoke and heat detectors for elevator control start in the elevator code. NFPA 72 tells you how to install and test them but not where to put them. The way NFPA 72 is worded is somewhat confusing.

Let’s look at a few applications. First, elevator lobbies. How many times have you seen smoke detectors in front of every elevator door? NFPA 72 says, “A lobby smoke detector shall be located on the ceiling within 21 ft. (6.4 m) of the centerline of each elevator door within the elevator bank under control of the detector.”

I had an elevator inspector once tell me that the main reason you see smoke detectors in front of each elevator door is because most inspectors see single elevator installations instead of a bank of them. So they are used to seeing one in front of every door.

In sprinklered elevator hoistways, you are going to need to install a smoke detector to initiate elevator recall and a heat detector to operate the shunt trip breaker to disconnect elevator power; a waterflow switch without time delay is allowed to be used instead.

You are required to install a control circuit to monitor the operating voltage of the shunt trip breaker and activate a supervisory signal on the fire alarm system if that power is lost.

If sprinklers are located at both the top and bottom of the hoistway, you will need to install the heat and smoke detectors in both locations. In addition, smoke detectors installed in the hoistway must be listed for the environment.

In the 2019 edition, language was added to require the fire alarm devices in the hoistway to be accessible for testing and maintenance from outside the hoistway. Obviously, this was added with the safety of the service personnel in mind.

I’m sure you have noticed that some newer buildings don’t have an elevator machine room anymore. Elevators without these rooms will still require fire alarm initiating devices where the motor control equipment or driving machine is located.

Remembering the purpose of each of these components can make your job much easier. If there are no sprinklers in the elevator, you more than likely will not have to install any fire alarm devices to control the elevator.

The exception would be if a smoke detector is needed to activate the elevator-hoistway smoke-relief equipment. So assuming the hoistway is sprinklered, the smoke detector is installed to initiate elevator recall and should activate first. This is intended to allow the elevator to recall to a designated level before the elevator power is disconnected, trapping occupants or firefighters in the elevator. Second, the heat detector would activate when the heat reaches a given temperature. This is to operate the shunt trip breaker to disconnect elevator power prior to discharge of water from the sprinklers. As you well know, water and electricity don’t play well with each other.

The codes now have requirements for elevators designated for fire service operation. In this case, NFPA 72 states that temperature and presence of smoke in all the elevator areas, including the elevator lobbies, have to be continuously monitored and displayed on the fire alarm system annunciator, or “other annunciators as approved by the AHJ”. This is required to provide the fire service with information of the conditions in those areas so they don’t have the elevator open in an unsafe condition.

Another relatively new requirement is for occupant evacuation elevators. This is only for use in buildings taller than 420 feet. These elevators are used to help occupants get to the exit discharge level quicker, and they are also allowed to be used as an alternative to providing additional means of egress as required in these tall buildings so as not to use up space for an additional stairwell. That space could be leased and earning income.

As always, be sure to review your adopted version of NFPA 72 when you are involved in installation or testing of fire alarm systems interfaced with elevators.

About the Author
Tom Hammerberg

Thomas P. Hammerberg

Life Safety Columnist

Thomas P. Hammerberg, SET, CFPS is an indepe       ndent fire alarm presenter and consultant residing in Jasper, GA. Tom served on multiple NFPA technical committees as well as actively participating in the ICC code making process for many years. He...

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