nfpa 13d/ avoiding obstructions

[twd22285]

In NFPA 13D 2007 edition, under 8.2.5.2.1 it states as follows: Pendent sprinklers shall be located at least 3 feet away from obstructions such as ceiling fans and light fixtures unless the requirements of 8.2.5.4 are met. 8.2.5.4 gives you the table to refer to at 8.2.5.4.2(position of sprinkler to avoid obstructions to discharge). in my case i have a surface mount light that will be coming down 6" off the ceiling, my sprinkler head deflector will be an inch below the ceiling. If i were to follow that table i would have to be a minimum of 4' away from the light where as 8.2.5.2.1 tells me 3' away is ok. I have several issues with the way this is worded and the clarity, or lack there of, thats given. #1, does this refer to all lights even if it is a recessed mount light fixture where no obstruction is created. And if thats the case then why even put 8.2.5.2.1 in nfpa 13d. #2, it does not say when one over rules the other. #3, does the light fixture have to act as a continuos obstruction in order for the table (8.2.5.4.2) to apply. this paticular project i am working on is very large for a 13d application (30,000 sq. ft home) so if i have to go four feet away from the fixtures, instead of three, it will raise the cost of the project considerably. Any clarification is much appreciated. Thank you in advance.


tony

 

[cdafd]

I am missing the conflict::: if you meet number 1 you are ok, if not go to the table:

8.2.5.2.1 Pendent sprinklers shall be located at least 3 ft (914 mm) away from obstructions such as ceiling fans and light fixtures unless the requirements of 8.2.5.4 are met.

and should only come in to play if there is an obstruction down from the ceiling

why the added cost??? are you possibly having to add heads??






8.2.5.2 Pendent Sprinklers.
8.2.5.2.1 Pendent sprinklers shall be located at least 3 ft (914 mm) away from obstructions such as ceiling fans and light fixtures unless the requirements of 8.2.5.4 are met.
8.2.5.2.2 The distance shall be measured from the center of the sprinkler to the center of the obstruction.
8.2.5.2.3 Where the sprinkler cannot be located 3 ft (914 mm) away from the obstruction (as measured from the center of the obstruction), an additional sprinkler shall be located on the other side of the obstruction.
8.2.5.2.4 Where the area of the fan blades encompass more than 50 percent of the area of the plan view, the sprinkler shall be installed in accordance with 8.2.5.4.






A.8.2.5 The objective is to position sprinklers so that the response time and discharge are not unduly affected by obstructions such as ceiling slope, beams, light fixtures, or ceiling fans. The rules in this section, while different from the obstruction rules of NFPA 13, Standard for the Installation of Sprinkler Systems, provide a reasonable level of life safety while maintaining the philosophy of keeping NFPA 13D relatively simple to apply and enforce.

 

[twd22285]

Well that's just it cdafd. Where does it say to use the three foot rule instead of the table? Usually when NFPA specifies to use something else when it applies, it explains what conditions need to be met to use the alternate method. In this case it does not specify. The only differnce in verbage used is the word "obstruction" vs "continuous obstruction".

And yes it would mean about 25 more heads through out the house. which is not much considering the house has 234 heads to start with.

thanks for taking a look cdafd. its much appreciated. It probably does not seem like much of an issue to argue, but this is the second time in the last 5 months this has come up in our office. And it seems like all four of the engineers here have a different opinion on it. So i thought i would get an outside look on it.

tony

 

[cdafd]

ok will try again
in rethinking this thing

for a simple light would go with the three feet minimum and call it good

now if that light runs eight feet across the ceiling and six inches down from the ceiling would apply the beam rule maybe.


I do case by case because sometimes you do not know what the fixture looks like till installed.

But three feet away from a six inch down obstruction should not affect the pattern much



and would say applies to only something below the ceiling level, not flush mount

 

[twd22285]

ok. i think we are on the same page then. i hear ya barking big dog!

thanks again

tony