FM global and ESFR sprinklers

[skdesigner]

I remember reading somewhere that FM Global does not require the inclusion of up to two ESFR sprinklers beneath an obstruction in the hydraulic calc like NFPA 13 does as long as you pipe to the head with the same diameter pipe as the branch lines.

I scanned through FMDS 2.0, 3.0 and the 8 series but cannot find it. Anybody familiar with this that can point me in the right direction?

Thanks in advance.

 

[Sdpaddler50]

Sk, you are absoultely correct. FM DS 2-0 does not actually indicate not to calc these, but there is no language indicating they need to be included in the hydraulic design as long as the heads are supplied by the same diamter as the exsting heads, same K factor head, etc. Its the same for heads added under power vents, etc. FYI, FM no longer refers to heads as ESFR. The new terminology is now "storage" mode sprinklers. Long story behind that. There is a link on the SFPE website written about 4 months ago if you want to check it out.

 

[skdesigner]

Shall do. Thanks for your help!

 

[skdesigner]

Found it. FM DS 2-0 Page 56

"The additional sprinklers installed under the obstruction as recommended above do not need to be added to the hydraulic design of the ceiling-level sprinkler system."

 

[skdesigner]

Interestingly enough, NFPA 13-2013 23.4.4.6.3.2 "Where piping to sprinklers under obstructions follows the same sizing pattern as the branch lines, no additional hydraulic calculations shall be required for sprinklers under obstructions."

 

[Sdpaddler50]

Glad you found the verbiage. One common pitfall i have found is some sprinkler contractors dont install the heads in the middle of the obstruction, and will often armover only several inches inside, as opposed to centering. I therefore make it clear in my letter that the heads should be centered. Not that big of a deal, but if a high ceiling is involved, and the obstruction footprint is large, it's best to have the heads centered. I am sure you know this, just a reminder.