quick question - above ceiling and below ceiling

[pipesnpumps]

I am pressed for time today. Where is the language in NFPA 13 about calculations for above and below ceilings.

If a contractor calc'd the head below the ceiling and didn't show the one above it flowing, that doesn't seem right to my recollection, but I can't put my finger on the right section, and have too much else to do.. Admittedly I am not very well versed in these details.

I know only one of the heads has to flow, but I am unsure if it needs to be the higher (more hydraulically remote) head or not. The calcs are very close to available water supply so I wanted to check.

Thanks in advance






Real world knowledge doesn't fall out of the sky on a parachute, but rather is gained in small increments during moments of panic or curiosity.

 

[chicopee]

I still have not figured out what you mean "about calculations for above and below ceilings".
I have to admit that expressing onself in writing is a son of a gun. I would hate to hear you verbally expressing your thoughts.

 

[pipesnpumps]

What's with the hostility?? I can effectively communicate, and people do not 'hate' it. Was the question really that unclear?

Answered my own question anyway:

"22.4.4.6.5 Water demand of sprinklers installed in concealed spaces or under obstructions such as ducts and cutting tables need not be added to ceiling demand."

So I interpret that language as, don't account for the above ceiling sprinkler [concealed space]. Therefore, it does not matter what elevation it is.. just calc the head that protects the below ceiling space.






Real world knowledge doesn't fall out of the sky on a parachute, but rather is gained in small increments during moments of panic or curiosity.

 

[NJ1]

What pipesnpumps is asking is where to find code reference in regards to hydraulic calculations when you have sprinklers above and below the ceiling. Right

 

[chicopee]

The reference to hydraulic calculation was not clear in the OP. There is no hostility, I just get miffed when the question is not clear.

 

[TravisMack]

I thought the question was very clear. Also, if the densities are the same in the concealed space and at the ceiling, I would likely want the concealed space head calc'd to account for the extra elevation.

I think the reference in 13 is saying that you don't have to flow both at the same time. However, I do think you have to prove the most demanding.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[skdesigner]

Don't forget to account for the strap tees/weld o lets and 1" pipe for the pendants. The uprights will likely be fed directly from the branchline, meaning the friction loss through their outlet fittings doesn't need to be added. Always good to calc both (though not simultaneously) just to be sure.

 

[pipesnpumps]

Thanks guys! It is great to have your input and experienced knowledge!!

I am taking an AFSA class in SC in July for my 2011 training, so hopefully with more time I can be better at reviewing the working plans and hydraulics, and know all the subtle details.

If I don't instinctually know everyhing about it, I simply don't have time to write an enforcable reivew comment; so I spend my lunch break and evenings learning this stuff, afraid I will miss it.

This is a tough job, being an AHJ. When I can't trust a 35 yr NICET it weighs heavy on me. And PE's are no different. Today I am fighting with a top 5 US engineering firm because they botched something very major and they know it, but want to save face.

About the only people I can trust are FPEs. I don't know why that is, but I like it. It must be they have such job stability they don't try to spin things to their favor. "Will revise and resubmit" is the appropriate response.

If I didn't abhorr always being in a hotel away from my family I'd go back to designing industrial plants. /rant/



Real world knowledge doesn't fall out of the sky on a parachute, but rather is gained in small increments during moments of panic or curiosity.

 

[TravisMack]

This is a tough job, being an AHJ. When I can't trust a 35 yr NICET it weighs heavy on me. And PE's are no different. Today I am fighting with a top 5 US engineering firm because they botched something very major and they know it, but want to save face.

This is one of my major pet peeves. No one likes to make a mistake, but until we are no longer human, we are going to make mistakes. Own up to it and work toward the best way to fix it. Just avoiding the issue or being difficult in order to "save face" just makes the solution that much more difficult further along in the project.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com