The second safety function is where smoke is detected at the top of a hoistway, or in an elevator machine room when located above the Designated Level. These hoistway/machine room's initiating devices are to be connected to two separate circuits. Circuit #2 (see above) is still used to recall the elevators to the Primary level, plus an additional circuit (labeled Circuit #3) to provide a safety warning to the firefighters.
Phase Two operation begins when firefighters enter the building and use a special emergency elevator key to override the Phase I Recall. Phase Two operation allows them to use the recalled elevators to quickly get to and from the fire floor. Since they are going to be using recalled elevators, they will need to be warned of any smoke developing in the hoistway or of a fire that could destroy the elevator machine room. To inform them of these dangerous situations, an amendment was added to the 1998 edition of the elevator code that provides for any new or retrofitted elevators to have a firefighters helmet (hat) symbol flash red in each of the affected elevator cars served by that machine room and in all cars operating in the affected hoistway(s).
Elevator machine rooms and hoistway detectors are also required to be individually zoned/annunciated at the fire command center and at any other annunciators in the building. In some larger buildings, you will need to provide this additional circuit for each additional elevator machine room and each individual hoistway. Any additional circuits (number these starting with Circuit #4, and up) must illuminate only their related elevator car's hat symbol and also separately annunciate the location of their associated initiating device(s). Remember, all circuits labeled #3 or higher, must also activate Circuit #2.
A third safety function for emergency shutdown may be required when other local/state codes specify the sprinkling of elevator hoistways. This feature is also know as a "shunt-trip" and removes operating power to the elevator hoistway/car. To perform this shutdown, you must be able to activate an initiating device prior to the activation of a sprinkler head. A rate-of-rise heat detector with 50 foot spacing, and a temperature rating below that of the sprinkler head, is usually used. This heat detector must be located within 2 feet of each sprinkler if it is to reliably cause an elevator to immediately shut down just prior to waterflow. Additionally, if a machine room is sprinklered or if any sprinkler heads are more than two feet above the bottom of the hoistway, these must also activate the shunt-trip feature. This shunt-trip will even override Phase Two Operation
Q: Smoke detectors operate with their own set of rules. Can you please touch on this subject?
A: Detector wiring must be monitored for integrity by a commercial fire alarm control panel. Smoke alarms are not permitted to be used. The detectors specified for elevator recall are system-type smoke detectors but only where their installation is permitted by the ambient conditions listed in NFPA 72. If the area is too dusty/dirty or the temperature is outside the smoke detector's listed specifications (such as below 32 deg F.) then you must use an alternate type of detection.
You do not have to install a smoke detector in a parking garage lobby. Even the 1997 edition of the elevator code changed the wording from "smoke detectors" to "automatic fire alarm initiating devices." Heat detectors are commonly used but any other appropriate initiating device is acceptable.
NFPA 13 (the 'sprinkler code') no longer requires a sprinklered hoistway that is only used for passenger elevators to have these detectors installed in them. Since the requirement for sprinklered hoistways was removed, so was the need for the smoke detectors. NFPA 72 states that you are not to install smoke detectors at the top of passenger elevator hoistways because of the increased potential for nuisance alarms and resulting disruption of elevator service. The 2002 edition of NFPA 72 also states that the AHJ is permitted to allow machine room and hoistway smoke detectors to initiate a "Supervisory Signal" instead of an alarm signal.