Originally Posted by gasaman
Any input on distances between sprinkler heads. My boss asked me today if I thought an existing head would need to be relocated, because they're moving a wall. The wall would now be on the other side of the head putting it inside of a closet. There is already a head inside of said closet, which is being enlarged. The next closest head the the new wall will be aprox. 11'. These are pendant heads hanging below a drop ceiling. Any advice would be appreciated.
This is really an old thread but seeing how there isn't much in the fire suppression forum I'll take a stab it in in case someone has a question in the future.
The answer is "it depends". It depends on the occupancy of the building and what kind of sprinkler heads are used.
Occupancy in sprinklers means what the use is. We have residential (this is what plumbers will be doing in one and two family dwellings), light hazard, ordinary hazard, extra hazard and storage occupancies.
Light hazard occupancies are similar to offices, schools, churches and hospitals. Using a standard sprinkler we can not exceed 256 sq. ft. per sprinkler, we can be up to 15'-0" apart and not more half the maximum distance apart, that's 7'-6" off any wall. There is one exception the "small room exception". Small rooms are defined as rooms not exceeding 800 sq. ft. (that's a big "small room") and in small rooms in a light hazard occupancy we are allowed to be up to 9'-0" off one of the walls
. We still have to maintain a maximum of 15' between heads and not exceed 7'-6" off any of the remaining walls. The small room exception only applies to light hazard occupancies.
An ordinary hazard occupancy would be grocery stores, mall stores, manufacturing and machine shops. Storage can not exceed 12'-0" in height. Once storage exceeds 12'-0" you leave ordinary hazard and enter the realm of high piled storage.
For ordinary hazard we have to maintain a maximum of 15'-0" between heads, can not exceed 7'-6" from any wall and the maximum coverage area can not exceed 130 sq. ft.. In other words if I want to space heads out 15'-0" apart on lines I can not exceed 8'-8" between lines.
15'-0"x8'-8"=130 sq. ft..
Measuring heads off walls can be tricky. I see this when they demise a store all the time. Say you got 10'x12' spacing which you see in most stores. The heads are 10' apart on lines and lines are 12'-0" apart which is 120 sq. ft. per sprinkler. Along one wall we have the heads 12'-0" apart, the next line over away from the wall is 10'-0" but the distance from the line of sprinklers closest to the wall is 6'-8". This is not correct. True, it is less than 7'-6" so we are fine there; if we take the width of the area sprinklers are covering it is half the distance between lines (5'-0"), the distance from the sprinkler to the wall is 6'-8" so it might appear the area of coverage is 11'-8"x10'-0"=116.6 sq. ft.but that isn't how it works. To find the width we work with you have to use the distance from one head to the next or double the distance between the wall and nearest head. In this case the actual area of coverage would be 13'-4"x10'-0"=133.3 sq. ft. which exceeds the 130 sq. ft. maximum allowed.
But then there are special extended coverage heads but in no case can a sprinkler exceed a coverage area of 400 sq. ft.. It isn't often we can use the world "never" but you can use it here.
Now we will come to the area some of you might work in. Residential sprinklers.
From NFPA 13D "Standard for the Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes"
8.1.3 Sprinkler Coverage.
188.8.131.52 Residential Sprinklers That Have Not Been Listed with Specific Coverage Criteria.
184.108.40.206.1 Sprinklers shall be spaced so that the maximum area protected by a single sprinkler does not exceed 144 ft2 (13.4 m2).
220.127.116.11.2 The maximum distance between sprinklers shall not exceed 12 ft (3.7 m) on or between pipelines.
18.104.22.168.3 The maximum distance from a wall or partition to a sprinkler shall not exceed 6 ft (1.8 m).
22.214.171.124.4 The minimum distance between sprinklers within a compartment shall be 8 ft (2.4 m).
126.96.36.199 Residential Sprinklers That Have Been Listed with Specific Coverage Criteria. Sprinklers shall be installed in accordance with the coverage criteria specified by the listing.
So far so simple. If you use a standard residential sprinkler it's pretty easy.. 144 sq. ft., not more than 12' apart, less than 8' apart and not more than 6' off a wall. Easy until you get to Section 188.8.131.52.
It might surprise you but there are literally thousands
of different kinds of listed sprinklers available. There are 20 different residential listed sprinklers on Viking Fire Protection's line you can see here here
. These are all different having very specific design and installation requirements.
Looking at cut sheet of the VK468 RESIDENTIAL PENDENT SPRINKLER
on the third page you can see these heads can cover an area up to 20'x20' (400 sq. ft.) if supplied with 20.0 gpm @ 16.7 psi. Even though the standard says a maximum of 12'-0" we can go to 20'-0" using this particular sprinkler because of its listing.
So to get back to the question there aren't any hard and fast rules. You need to know the occupancy, the design criteria, the exact sprinkler being used. Except for the sprinkler being 11' off the wall (the max is always not more than 10' regardless of type of pendent head used) I would be hard pressed to answer this correctly just by walking in and looking up.