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An assortment of building occupancy examples are classified in Sec. A.5.2 of the NFPA 13 Appendix. The following are brought up as light hazard occupancies: offices, churches, schools, museums, auditoriums, library seating areas, restaurant seating areas, and unused attics. The greatest or most complete or best possible sprinkler spacing (protection area) for these is noted in Table 8.6.2.2.1(a) if popular sprinklers are used. Usually, the greatest or most complete or best possible limit is 225 square feet for light hazard on a hydraulically calculated system. However, when exposed construction is combustible, with structural members spaced less than 3 ft. apart, the greatest or most complete or best possible coverage limit shrinks to 130 square feet. Ordinary hazard Group 1 occupancies include laundries, restaurant service areas, and automobile parking garages. Ordinary hazard Group 2 occupancies include the aforementioned arid cleaners, automobile fix and services areas, auditorium stages, woodworking plants, post offices, and stack room areas of libraries. Standard sprinklers protecting all frequent hazard occupancies shall not cover an excess of 130 square feet per head (Table 8.6.2.2.1(b). Extra hazard occupancy examples include printing plants, paint and varnish dipping operations, plywood manufacturing, solvent cleaning, and plastics processing. Maximum sprinkler spacing for these occupancies is fixed to 100 square feet. However, where the required design density is less than 0.25 gpm/sf (and this goes for high-piled storage as well), a shelter area of up to 130 square feet per sprinkler is allowable (Table 8.6.2.2.1-c). It must be brought up that mercantile insurance carriers and advisors invent their own creative writing of recognized artisti value containing more extensive listings of occupancy examples and classifications than does the NFPA 13 standard, info which oftentimes comes in handy when making an occupancy classification determination. Design Density Criteria The NFPA 13 Density / Area Curves are found in Fig. 11.2.3.1.1. When hydraulically calculating a light hazard sprinkler system, the design density applied is distinctively 0.10 gpm/sf over a 1500 square foot (the most hydraulically demanding) area of operation. To start out a calculation, the architect starts with the end-sprinkler and works “backwards” to the water supply source. Suppose that the sprinklers are spaced 14 ft. isolated on branch-lines that are 12 ft. apart. Our square foot coverage then, is (12 x 14) 168 square feet. Q (in gpm) is determined by multiplying the density by the square foot coverage (.10 x 168), so we recognise that we’ll need 16.8 gallons per minute (Q) discharging out of the end sprinkler. The square root of the required end-head pressure is determined by “Q” divided by “K”. If the design density is 0.10 and the K-factor of the sprinkler head is 5.5, we may assure our end-head pressure by dividing 16.8 by 5.5, and squaring the sum to obtain a 9.33 psi figure. 9.33 psi is the required end-head pressure. To double-check, we may plainly plug in the numbers while performing the following equations to make sure that they match: Q= K times the square root of the pressure, K= Q separated by the square root of the pressure, and the design density equals Q separated by the square foot coverage. If our area of operation remains 1500 square feet, our design density will change to 0.15 for Ordinary hazard Group 1 occupancies and 0.20 for Ordinary hazard Group 2 occupancies. Everything changes when extended-coverage sprinklers are employed. Let’s suppose that we determine to extend our coverage to 324 square feet in a light hazard office, spacing sprinklers 18′ x 18′ apart. Now we ought to refer to the sprinkler manufacturer’s data sheets for direction. If we choose to install Tyco EC-11 pendent sprinklers, the selective information sheets dictate that our end-sprinkler will have to discharge a minimum of 33 gpm at 8.7 psi. This means that our design density (Q separated by the square foot coverage) is still 0.10 gpm/sf. The K-factor of this queer sprinkler is 11.2, which we may validate by the equation K= Q disunited by the square root of the pressure. Extended-coverage sprinklers for usual hazard occupancies work the same way. For example, we could use the Tyco EC-14 extended-coverage pendent sprinkler (K=14.0) in a (Ordinary hazard group 1) restaurant service area to protect an 18′ x 18′ area, but here the selective information sheet parameters require a 49 gpm minimum discharge at 12.3 psi for the end-sprinkler. In other words, Q= 49, K= 14.0, the square root of the pressure is 3.51, and the coverage is 324 square feet. All the equations match, including the required design density (0.15) which is received by dividing Q by the 324 sq. feet. Of course, the local water supply will have to still be competent to satisfy the resulting overall sprinkler scheme demand. In order for that to be accomplished, more spectacular scheme piping is installed to deliver the further and added gpm necessitated by the extended-coverage heads. Sprinkler discharge characteristics are outlined in cogent form in Table 6.2.3.1- these outline the differing K-factors for sprinkler identification. One other handy table to reference for sprinklers in NFPA 13 is Table 6.2.5.1, which deals with classifications and temperature ratings. To be utterly sure of code compliance with respect to sprinkler elevations, we refer to Sec. 8.6.4.1 in NFPA 13. The allowable distances noted underneath roofs, beams, or ceilings are always measured to the sprinkler deflector. It is worthy of acceptance or satisfactory for designers to consult info sheets for suitable distances underneath ceilings for specific sprinkler types, though the safe bet is to call for a distance amongst 1″ and 12″ underneath the undersurface of the roof deck. The closer sprinklers are to the ceiling, the quicker they will operate. But caution will have to be exercised because ofttimes severe interferences to lateral water distribution may result from very close sprinkler placement to the ceiling. For all instances, the minimum of 1 inch (in the code) is to concede for the installation and remotion of upright sprinklers. When sprinklers are installed under pitched roofs, the most eminent sprinkler deflector (Sec. 8.6.4.1.3.1) may extend 3 ft. down from the most eminent peak.
24 of 27 people found the following review helpful. 11 of 12 people found the following review helpful. I like the concept. It’s wonderfully easy to adjust compared to the traditional oscillating sprinklers, but this product is engineered badly. One has to wonder if they ever do any design verification testing on their products. They certainly couldn’t have done much on this piece of junk. 6 of 6 people found the following review helpful. I was skeptical that the 4200 model with water flow control would make that much of a difference, because I figured I could simply control flow at the faucet. Thankfully I was wrong! I turn up the water pressure at the faucet, turn down the water flow at the sprinkler and it works beautifully in even the smallest areas. Continues to oscillate just fine even when doing a small 4′X 6′ patch of grass. |
Not worth the trouble!
Junk.
Water flow control really makes a difference…