NFPA 13 ESFR Sprinkler Obstructions

[Always Learning]

Hello - New to this forum.

I am looking for some clarification on 14.2.11.1 2019 NFPA 13

Does 14.2.11.2 (2) mean as long as my light fixture is 2' wide or less and horizontally 1' or greater from the sprinkler deflector I can ignore the spacing requirements of 14.2.11.1.1 which refers you to both Table and Figure 14.2.11.1.

The other question is relating to definition of 2' wide. This would mean a 2'x4' light would not allow you to comply with 14.2.11.2 (2). If using a 2' x 4' fixture that must comply with 14.2.11.1 because of the 4' length of the fixture?

With the advancement of LED lighting there are several 2'x2' LED highbays available that would make installation coordination much simpler for these fixtures since the ESFR heads are installed pretty tight to the roof deck

Thank you for any input.

 

[UFT12]

Does 14.2.11.2 (2) mean as long as my light fixture is 2' wide or less and horizontally 1' or greater from the sprinkler deflector I can ignore the spacing requirements of 14.2.11.1.1 which refers you to both Table and Figure 14.2.11.1.

Since 14.2.11.2(3) is within 14.2.11.2, my understanding is that at least for the bottom of the obstruction and as long as the obstruction is at the ceiling area (see how 14.2.11.1.1 is written), fig. & tbl 14.2.11.1.1 must be observed in this case too.

The other question is relating to definition of 2' wide. This would mean a 2'x4' light would not allow you to comply with 14.2.11.2 (2). If using a 2' x 4' fixture that must comply with 14.2.11.1 because of the 4' length of the fixture?

When applying 14.2.11.1, the height & elevation is what matter most and how high comes to the sprinkler head. The length (i.e. 4') is not to be considered since the least dimension matters (i.e. 2'). See stipulation of 14.2.11.2(2) (i.e. width).

See also the requirements of FMDS0200, par. 2.2.3.5 which are more or less the same as per NFPA 13, a bit more comprehensively written.

 

[Always Learning]

Since 14.2.11.2(3) is within 14.2.11.2, my understanding is that at least for the bottom of the obstruction and as long as the obstruction is at the ceiling area (see how 14.2.11.1.1 is written), fig. & tbl 14.2.11.1.1 must be observed in this case too.




SORRY - I WAS NOT SURE HOW TO END QUOTE BEFORE I ADDED MY QUESTION BELOW



But 14.2.11.2 states 'in accordance with one of the following' not all of the following. Would that not mean if I complied with (2) I meet the intent of the code. Where I am confused (I think) is 14.2.11.2 seems to contradict 14.2.11.1.1. There is additional explanation in the Annex A section but it was not helpful

 

[UFT12]

What I meant is that 14.2.11.1.1 still applies and need to be checked. So imagine a case where 14.2.11.2(2) is satisfied but (3) is not. So by taking measures to satisfy (3) you are practically satisfying (2) as well (or (4)). At least this is my interpretation.

 

[TravisMack]

Let me see if I can clarify a bit of this:
14.2.11.1.1 is commonly referred to as the beam rule. Look at this diagram. The obstruction prevents discharge from going over the "beam". So, if your obstuction is such that it prohibits water from going over then you have to space a certain distance away so you can throw over it.

For the other parts, look at the definitions in Chapter 3.
Continuous obstruction affects discharge of 2 or more sprinklers. Noncontinuous (aka isolated) affects the discharge pattern of 1 sprinkler.

For isolated obstructions BELOW elevation of sprinklers, like a light, it says meet one of the following:
(1) put a sprinkler below it
(2) If the width (narrow dimension) is 2' or less, be 1' away from the sprinkler.
(3) meet the "beam rule" - 14.2.11.1.1
(4) If obstruction 2" or less in width (small pipe/conduit for example) and is located 2' below and 1' horizontal to sprinkler, no extra needed.
(5) if the manufacturer's come up with some special criteria based on testing

So, stay 1' away from your lights that don't exceed 2' in width and you are good to go.

Travis Mack, SET, CWBSP, RME-G, CFPS
MFP Design, a Ferguson Enterprise

http://www.mfpdesign.com

 

[UFT12]

It 's true the stipulation 'in accordance with one of the following' seems to allow to disregard any other case as long as at least one is true. But in this case I personally disagree (OK I will however disregard case (5)). Consider the following situation as shown below. Assume an ESFR sprinkler head and a light fixture or what ever rigid obstruction that may be.

14.2.11.2(2) is satisfied.
14.2.11.2(3) is not.

Can I get away with it just because (2) is good? I don't think so.
FMDS0200 states in "2.2.3.5.2 Obstruction to Inner Core Discharge Pattern of Ceiling-Level Storage Sprinklers" the following "In addition to the recommendations in Sections 2.2.3.1 through 2.2.3.4 and Section 2.2.3.5.1 (beam rule), install Storage sprinklers as recommended in Table 20 and Figures 34...". It is an other standard, other criteria, we know the differences. But it kinda gives the intent on the subject of ESFR which by the way are not intended just for life safety issues.

Also I 'm not sure about the following 'and'. The stipulation in 14.2.11.2(4) is using 'or', not 'and'.
... If obstruction 2" or less in width (small pipe/conduit for example) and is located 2' below and 1' horizontal to sprinkler, no extra needed....

 

[TravisMack]

The FM "umbrella" diagrams state that obstructions aren't permitted in the area except as noted with the items like the 1' away from joist, etc.. Table 20 in 2-0 gives the criteria for these areas. This stuff does get quite interesting as you go along with the spacing criteria.

Travis Mack, SET, CWBSP, RME-G, CFPS
MFP Design, a Ferguson Enterprise

http://www.mfpdesign.com

 

[Always Learning]

I think the NFPA should consider re-writing that section of the code. Saying it as 'in accordance with one of the following' leads you to believe if you comply with one you are (as TravisMack stated) good to go. There are several instances in the NEC (NFPA 70), a code which I am much more familiar with and have worked with for 25+ years, which are written in a similar manner and in the case of that code from my experience if you comply with one that is all that is required. I tend to agree with TravisMack's way of thinking but 14.2.11.1 does indicate lights as an obstruction so compliance with said section is required. The real question becoming why have 14.2.11.2 at all than? I think an actual ruling from NFPA themselves would be helpful but unfortunately I am not a member (yet). Ill have to look at the FM items you reference as well.

 

[TravisMack]

I think it is quite clear as it is written. Basically, you add sprinklers under it if you can't comply with the other criteria. FM is written the same way. Look at that Table 20 in 2-0. It gives you very similar criteria. FM is obviously a bit more stringent as they typically are.

Travis Mack, SET, CWBSP, RME-G, CFPS
MFP Design, a Ferguson Enterprise

http://www.mfpdesign.com