Sprinklers and Elevators: Can They Coexist?
First one must define which types of elevators are considered. Elevators are defined as vertical transport hoisting and lowering mechanisms, equipped with a car that moves within guides and serves two or more landings. Numerous other types of lifts and similar devices are not applicable to these requirements. They include manlifts, platforms, conveyors, wheelchair lifts, dumbwaiters, etc. These may be covered by other codes including ASME, ANSI, the local building official, OSHA or their own unique code requirements.
In most cases, the sprinklers are provided due to code requirements. NFPA 13, Standard for the Installation of Sprinkler Systems, is the governing code. It requires sprinklers in elevator hoistways and machine rooms. At one time, sprinklers were not specifically required here even if the building was fully sprinklered. Therefore, sprinklers were often omitted from these areas. This is no longer the case, since the codes now specifically call for their installation. The sprinkler requirements will be explained in the following paragraphs.
--Sidewall spray sprinklers are normally installed at the bottom of each elevator hoistway, not more than two feet above the floor of the pit. There are exceptions, however. For enclosed, noncombustible elevator shafts that do not contain combustible hydraulic fluids, the sprinklers at the bottom of the shaft can be deleted. How is this accomplished? Vegetable oil in lieu of combustible hydraulic fluids is allowed, but this requires the requisition to specify it and then ensure submittals provide it and that it's properly installed. You must rely on many variables being provided by a third party.
--The sprinklers in the pit are to protect against fires caused by the debris that accumulates over time. Ideally, the sprinklers should be located near the side of the pit, below the elevator doors, where most debris accumulates. However, care should be taken so the sprinkler location does not interfere with the elevator toe guard, which extends below the face of the door opening. ASME A17.1, Safety Code for Elevator and Escalators, allows the sprinklers within two feet of the bottom of the pit to be exempted from the special arrangements of inhibiting waterflow until elevator recall has occurred. The sprinkler in this location is not considered a hazard. People and electrical devices are not located in this area.
--Upright or pendent spray sprinklers are normally installed at the top of elevator hoistways. The exception is when noncombustible hoistways of passenger elevator with car enclosure materials that meet the requirements of ASME A17.1, Safety Code for Elevators and Escalators, are used. Most new and existing shafts meet these requirements. Passenger elevator cars that have been constructed in accordance with ASME A17.1, Safety Code for Elevator and Escalators, have limited combustibility. Materials exposed to the interior of the car and the hoistway, in their end-use composition, are limited to a flame-spread rating of 0 to 75 and a smoke-development rating of 0 to 450.
--Sprinklers are also required in elevator motor or machine rooms. The type of head is dependent upon whether or not a ceiling is present. NFPA requires an ordinary or intermediate temperature rating on the head.
--A flow switch needs to be provided to detect water flow. With a flow switch, there needs to be a means to test the device; therefore an inspector's test valve with sight glass and a discharge to drain should be provided.
--How the piping is installed is critical. ASME A17.1c, section 2.8.2, requires that the installation of the mains and risers be located outside the hoistway. Sprinkler piping shall serve one level in the hoistway, and all risers and returns shall be outside the hoistway. You cannot run one sprinkler branch horizontally from one floor and then run vertically up or down the shaft. Piping must run from each floor level, then to the top or bottom of the shaft. To minimize leakage and damage, the least amount of piping in the shaft is desired. But if the machine room is located on the roof above the shaft, it is acceptable to run piping through the shaft to feed the machine room. Common sense prevails here.
--The presence of sprinklers requires the installation of a system to automatically disconnect main power, prior to the application of water. A shunt trip system is normal. A shunt trip is an electrically operated tripped breaker. The shunt allows the breaker to open on signal from another source, e.g. smoke or heat detector.
--When standard sprinkler protection that conforms to the requirements of NFPA 13 is provided, means should be provided to automatically disconnect the main power supply to the affected elevator upon or before the application of water from the sprinklers located in the machine room or in the hoistway more than two feet above the floor. This code doesn't care about the sprinklers at the bottom of the shaft. It is concerned about water discharging onto people and equipment, which could cause injury, electrocution, premature shutdown and loss of lives. The elevator's job is to bring the personnel to a safe level of discharge. Sprinkler operation may impede this operation, due to the application of water onto sensitive electrical equipment.
--NFPA 72, the National Fire Alarm Code section 3-9.4, requires elevator shut down. If a pressure or waterflow switch is used to shut down the elevator power immediately upon or prior to the discharge of water from sprinklers, the use of devices with time delay switches or time delay capability should not be used. Also, where heat detectors are used to shut down elevator power prior to sprinkler operation, the detector should have both a lower temperature rating and a higher sensitivity, as compared to the sprinkler. This is accomplished by using a heat detector rated at 135 degrees F and a sprinkler head rated at the standard 165 degrees or 212 degrees F. This ensures the heat detector will activate first. Note that NFPA 13, section 5-13.6.2 requires sprinklers in elevator machine rooms or hoistways to be ordinary or intermediate temperature rating. The definition in the code for an ordinary sprinkler head is 135 degrees to 170 degrees F. Use the proper temperature heads. NFPA allows 165 degrees F, but to be sure, 212 degrees F heads are a safer design. Also NFPA 72, 3-9.4.2 requires that if heat detectors are used to shut down elevator power prior to sprinkler operation, the detectors should be placed within two feet of the sprinkler head. ASME A17.1c/2000, section 126.96.36.199.3 does not allow smoke detectors to be used to activate sprinklers in these spaces or to disconnect the main line power supply.
Potential Sequence of Events During an Occurrence
- 1. Smoke activates detector in elevator or machine room.
2. Emergency elevator recall is initiated.
3. Elevators associated with machine room or hoistway are sent to the required floor of recall.
4. Heat buildup causes heat detector to activate.
5. Shunt trip operates, disconnecting power from elevator.
6. Heat buildup continues; sprinkler head(s) activate.
If there is an existing elevator and machine room and the area is being retrofitted with sprinklers, substantial elevator and electrical improvements need to be made to these existing systems. The addition of sprinklers to these areas seriously affects other disciplines. Proper communication between the architect, electrical engineer, fire protection engineer and local code officials, needs to occur.
If the existing building is being renovated and there is an elevator, but it's not sprinklered, it does not need to be retrofitted with a sprinkler system. This is true unless there is a change in occupancy. The local official may require all code violations be brought up to date; therefore, check with your local code enforcer.
Other options include preaction systems to further safeguard that water is not being applied to these areas. Typically pre-packaged systems are used for high-rise buildings, due to their ease of installation. They require additional costs compared to conventional wet systems or built-in place preaction systems.
In conclusion, it is recommended that an integrated design approach should be taken, with all building trades people and building officials made aware of the design decisions. The design of the elevator requires a coordinated effort. Everyone must be sensitive to each other's needs and requirements. In the end, a successful system and a pleased owner will be the result.