Hotel and motel fire sprinkler system installations open up options to designers not always available for other type of occupancies. They are also capable of providing additional challenges not seen in typical office buildings, warehouses and mercantile occupancies. If you can take advantage of the additional design options while keeping the cost of tackling the unique challenges to a minimum, most of the basics remain the same as for any other fire protection system design.
Sprinkler systems for all hotels and motels can be designed under NFPA 13, Standard for the Installation of Sprinkler Systems. All hotels and motels up to four stories in height can be designed per NFPA 13R,Standard for the Installation of Sprinkler Systems in Residential Occupancies up to and Including Four Stories in Height. The primary difference between the requirements of these two standards are:
-The total area does not exceed 24ft2;
-The least dimension does not exceed 3ft; and
-The walls and ceilings are constructed of a noncombustible or limited-combustible material as defined by NFPA 220, Standard on Types of Building Construction.
NFPA 13R, Standard for the Installation of Sprinkler Systems in Residential Occupancies up to and Including Four Stories in Height - 2007 Edition:
-The area of the space does not exceed 24ft2;
-The least dimension does not exceed 3ft; and
-The walls and ceilings are surfaced with noncombustible or limited-combustible materials as defined by NFPA 220, Standard on Types of Building Construction.
Other editions of these standards may be enforced by local jurisdictions.
Water Supply RequirementsThe vast majority of these types of buildings will be classified as Light Hazard occupancies and, thus, require a design density of 0.10 gpm/ft2 over a design area of 1,500 ft2. These Light Hazard areas include common areas, guest rooms, bathrooms (public and guest rooms), restaurant seating areas (if applicable), and indoor pool rooms. Areas such as mechanical rooms, laundries and kitchens would be considered Ordinary Hazard (Group 1) occupancies requiring a design density of 0.15 gpm/ft2 over a design area of 1,500 ft2.
Finally, storage closets would be considered Ordinary Hazard (Group 2), needing a design density of 0.20 gpm/ft2 over a design area of 1,500 ft2. A total fire hose stream demand of 100 gpm for Light Hazard and 250 gpm for Ordinary Hazard are required to be included in the hydraulic calculations. Multi-function rooms and retail areas also classify as Ordinary Hazard.
The applicable local code must be reviewed to determine if a Class I standpipe system is required. Standpipes are typically required for buildings above a certain height or with large assembly occupancies. The water supply for a standpipe system in a fully sprinklered building will range from a minimum of 500 gpm to a maximum of 1,000 gpm. Fire pumps are usually required to provide adequate pressure for standpipe systems.
Evaluating Existing Water SuppliesPrior to any design, an analysis of the existing water supply must be conducted. This is accomplished by means of conducting a water flow test. This analysis determines the static water pressure within the water main system, the volume of water flow available, and the flowing pressure of the existing water system. The water flow analysis must take into consideration any condition that may affect the results. These considerations include, but are not limited to: 1) variation in daily and seasonal water usage, 2) anticipated changes in future water usage, and 3) changes in operating pressure at the pumping stations and for elevated water storage tanks.
With this information it can be determined what size water main will be optimal for the building as well as whether a fire pump will be required to boost water pressure to an adequate level. There is a balance required when it comes to water main and fire pump sizing. You can reduce cost by limiting the size of the incoming water service but perhaps lose that entire savings on the required increase in fire pump size.
You can keep the fire pump size down to save on initial pump cost, but may have to increase your sprinkler pipe sizing - increasing both the material cost and the installation cost. Oversized items can also unnecessarily increase costs. All these items must be weighed and an optimal balance struck.
Design ConsiderationsHotels and motels often bring other design options and challenges. As noted earlier, in many cases fire sprinklers may be eliminated from hotel and motel bathrooms and closets.
Another design option that is often taken, as it provides a significant cost savings, is the use of extended coverage fire sprinklers. As the name implies, these fire sprinklers provide additional coverage compared with standard coverage fire sprinklers. A typical guest room orientation consists of a rectangular shape with the bathroom and entry door situated at one end and the exterior wall located at the other end. The Building Code requires the sprinklers in the guest rooms to be either residential sprinklers or quick response sprinklers.
The distance from the inner bathroom wall to the exterior wall is typically more than 15 feet in length but not more than 22 feet. The maximum coverage area of a standard coverage quick response fire sprinkler is 15 feet. Extended coverage fire sprinklers are often rated for areas up to 16 feet wide by 24 feet in length. By utilizing extended coverage fire sprinklers, a contractor can eliminate one additional fire sprinkler per guest room. This would result in a significant cost savings.
A design challenge often found within hotels and motels is low floor to ceiling heights. This increases the difficulty in concealing the fire sprinkler piping and, thus, increases the importance of coordination with other trades. Many corridors do not have suspended ceilings. A typical solution to this challenge is to locate the fire sprinkler piping within the guest room entry way and bathroom where there is often a suspended ceiling. Another possibility is to locate the sprinkler piping within the common corridor and conceal it in a soffit.
Fire Protection System ElementsMany fire sprinkler systems have the same basic components. As noted earlier, typical hotels that are more than four stories in height require a standpipe system with 2-1/2" fire hose valves for fire department use. Depending on the local codes, these standpipes may require 65 psi or 100 psi at the topmost hose valve. In areas where the city water pressures cannot meet this demand, a fire pump is required to increase the water pressure and flow to the required levels.
A sprinkler riser with floor control valves, water flow switches, tamper switches, and a test and drain valve connected to a drain riser are typically located within a stairwell. The water flow and tamper switches are installed in order to monitor the sprinkler system and should be connected to the fire alarm system.
The tamper switches tell the building alarm panel if a control valve is in the “closed” position. Similarly, the water flow switch alerts the fire alarm panel when water is flowing within the system and on what level water is flowing.
The test and drain riser allows for the required periodic system testing of these monitoring devices, as well as allowing the draining of a system for repair or alteration. A fire department connection is required to be installed on the exterior of the building. This device is utilized by the local fire department in order to significantly boost the fire sprinkler system pressure and flow upon arrival to the building. This is accomplished via a connection to the fire department’s pumper truck.
It is important that proper system documentation and instruction in the operation of the sprinkler system is provided to the owner in order to facilitate proper maintenance and testing, per NFPA 25Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems.
If properly installed and maintained, a fire sprinkler system is one of the single most important life safety features within a building. This is especially true for occupancies such as motels and hotels where occupants are sleeping, cooking, or living for extended periods of time. Fire sprinkler systems provide early suppression of a fire, as well as notifying the building occupants and local emergency services of a fire. So the next time you check into a hotel or motel, check to make sure that it is protected by fire sprinklers.