six foot minimum

[cdafd]

Have not had a chance to read 13, just trying to confirm if you have sprinkler lines on a slanted ceiling do you measure the minimum required spacing from pipe to pipe on the slant, or is it as you look at the lines from the floor and measure a straight line say from point a" pipe to point b" pipe??

 

[dbill74]

Along the slope. NFPA 13, 2003 ed. illustrates how locate heads in a peaked roof or ceiling in 8.6.4.1.3. The figures in NFPA 13 will help.

 

[TravisMack]

space on the slope, calc on the flat. That is how I was always taught.

Travis Mack
MFP Design, LLC

 

[ContractorDave]

If the concern here is in regards to the minimum spacing of the 6' rule in regards to cold soldering, as opposed to those of hydraulics, which I think is what you are asking, then I respectively disagree with Travis and dbill. These sprinklers should be measured and spaced on the horizontal plane.

Regards
Dave

 

[TravisMack]

Dave:

What do you do with the 15' maximum then. Do you space on the flat and just let it exceed the max distance on the slope. Or, do you take the conservative view and space on the flats for minimums and on the slopes for maximums? I don't mean this to be argumentative. I am curious as to how others address these issues when they come up.

T

Travis Mack
MFP Design, LLC

 

[ContractorDave]

Travis

Excellent question. Personally I would tend to be conservative in small applications, but if you are doing an NHL sized hockey arena, costs may quickly become a factor in having the AHJ decide the issue. If an engineer is satisfied that spacing sprinklers at > 15' centers on a slope still provides the required densities and the AHJ is happy with this, that would suit me.

Regards
Dave

 

[FFP1]

I would have to research NFPA to be certain, but I think the maximum distance should be measured along the slope and the minimum distance should be measured horizontally.

Slope creates several issues; therefore, the most prudent approach would be to apply the minimum 6ft. requirement and the maximum 15 ft. (or the more stringent maximum sprinkler spacing as outlined by NFPA) measured horizontally and along the slope. My personal opinion is this would be the best approach from an engineering/design standpoint when dealing with sloped ceilings.

 

[MGXFP]

8.6.3.4.1
Unless the requirements of 8.6.3.4.2, 8.6.3.4.3 or 8.6.3.4.4 are met, sprinklers shall be spaced not less than 6 ft. on center.

The three exclusions above include adding baffles between sprinklers detailed in 8.6.3.4.2, In-rack sprinklers or old style sprinklers in fur vault storage.

It sounds like the 6 foot is measured on the slope.

 

[cdafd]

If the concern here is in regards to the minimum spacing of the 6' rule in regards to cold soldering, as opposed to those of hydraulics, which I think is what you are asking

yes that is the question cold soldering

 

[FFP1]

cdafd is 100% correct! The minimum 6 ft. rule is to prevent cold soldering.

 

[ContractorDave]

The purpose of the 6' rule as stated is to prevent cold soldering. Water tends to fall down, taking into account gravity and all that other stuff that concerns engineers on paper and sprinkler fitters on ladders... This is why I would reason that the rule would be applied on the horizontal. 6' centers on a 45 degree slope is only 4' 4" or so. We are not concerned about densities here. Just that a sprinkler within the NFPA dictated 6' will possibly cold solder another.

Regards
Dave

 

[TravisMack]

Dave:

If we take the same example of a 45° slope with 15' max on the horizontal, that would be 21' on the slope. I don't think that could ever be allowed.

Again, I have always done 6' on center minimum on the slope as that is how I was taught that NFPA 13 req'd. I can see the argument for the 6' being measured horizontally, and will likely start applying that to my work. However, I think the max still must be measured on the slope no matter what the slope is. You may run into an issue with something like a 67° slope where 15' on the slope is <6' on the horizontal. However, I can't say I have come across something with a slope to that extent.

This has been an interesting thread.

Travis Mack
MFP Design, LLC

 

[FFP1]

As I stated in my earlier post.....the most prudent approach would be to apply the minimum 6ft. requirement and the maximum 15 ft. (or the more stringent maximum sprinkler spacing as outlined by NFPA) measured horizontally and along the slope. As long as we all apply both limits (6 ft. & 15 ft.) to both orientations, there should not be any issues. My personal opinion is this would be the best approach from an engineering/design standpoint when dealing with sloped ceilings. The increased cost will not be very significant and this will help to eliminate cold soldering as well as unprotected areas. The sloped ceilings already cause enough problems with the slight delay in sprinkler activation, minor obstruction of the umbrella pattern (in certain circumstances) and sometimes having the sprinklers horizontally installed with the sloped ceiling rather than the protected floor. Sprinkler heads are simply not as efficient when installed under a sloped ceiling.

 

[ContractorDave]

Travis

"...If we take the same example of a 45° slope with 15' max on the horizontal, that would be 21' on the slope. I don't think that could ever be allowed..."

Other than as FPP1 observes that sprinkler heads don't work well under sloped ceilings; I would assume that if we are not concerned with minimums and cold soldering, it is still in the end a density matter and the distance between sprinklers on the pipe itself shouldn't really matter? Given this line of thought, ALL centers should be measured on the horizontal?

I agree. This has been an interesting thread over a seemingly simple issue.

Regards
Dave

 

[TravisMack]

Dave:

Sprinklers must be placed with respect to coverage and activation time. Would putting a SSU at 15'x21' increase the response time to an unacceptable level? I realize the distance along the pipe has no impact. I have had that discussion with a reviewer when my flat ceiling grid and structural steel were 45° to each other. This had me with +-18' pipe cuts between sprinklers in a horizontal ceiling. But, the actual dimensions were < 15' between sprinklers measured in a x,y,z dimension.

While sprinklers may not operate as well under sloped ceilings, I do think we have to find a way to deal with them. Slopes aren't going away anytime soon. I don't think many flat roofs will be installed in areas with heavy snow loads and architects love their sloping ceilings The reduced performance and activation time is likely why we have the 30% increase when sprinklers are under sloped ceilings >2:12.

Travis Mack
MFP Design, LLC

 

[FFP1]

The 30% increase reference by TravisMack is correct; the reduced performance and activation time issues were the driving forces behind the 30% increase. ESFR sprinklers are strictly limited to flat ceiling systems (no more than 2 in 12 slope) due to these same issues.

 

[cdafd]

finally had a minute to look at nfpa 13.

If you look at figure 8.6.4.1.3.1 a and b nfpa 13 2002
when you are spacing them it looks like you measure along the slope.

so I would also measure the minimum six feet apart along the slope.

Just had one of those strange lay outs that I had to inspect and was not sure, along with other things on the mind.

 

[ContractorDave]

Interesting Still!

Thx gentlemen. My quota for new things learned this week is now full! (Kidding .. never stop learning )

Have a great day.

Regards
Dave

 

[SprinklerDesigner2]

It is on the slope.

From NFPA 13 - 2002

8.5.3 Sprinkler Spacing.
8.5.3.1 Maximum Distance Between Sprinklers.
8.5.3.1.1 The maximum distance permitted between sprinklers shall be based on the centerline distance between sprinklers on the branch line or on adjacent branch lines.
8.5.3.1.2 The maximum distance shall be measured along the slope of the ceiling.
8.5.3.1.3 The maximum distance permitted between sprinklers shall comply with the value indicated in the applicable section for each type or style of sprinkler.