When you have a 2 level hydraulic elevator in a fully sprinklered building and the sprinkler company has installed a sprinkler head in the pit, do I need to install a heat detector adjacent to the sprinkler head?
Reference Section 21.4 of NFPA-72, heat detectors are required to shunt power to the elevator prior to the flow of water from the sprinkler.
Yes, heat detectors are required at the top of the shaft and are supposed to operate prior to the sprinkler head activating for the purpose of activating the shunt trip breaker so that the power inside the elevator car is turned off prior to the sprinkler head being activated so that once the sprinkler head does activate, it does not dump water on any live electrical circuits that are inside the elevator car.
Now when we have a sprinkler head inside the elevator pit and it activates, the water is not going to flow upwards to get to the top of the elevator car and most likely water from a pit head will not get inside the elevator car, so why would you want to shunt trip the power to the elevator car?
When the sprinkler head in the pit activates, the associated water flow switch should activate and activate the alarm.
Activation of a detector occurs faster than a sprinkler head even if the head is early response type. Therefore, I think that detectors should be placed in hoistways for recall operation of the elevator in order to prevent people from smoke influences.
Besides, in addition to my interpretations, NFPA 72 - Section 21.3.7 explains how detectors should be installed if sprinkler heads provided within the pit.
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