Design Area of sprinklers in Multi-Hazard occupancies 2

[Aikah-Eng]

Hi Dears,

I would like to confirm if my fire system design concept and steps are correct or not in this example project that I'm trying to design practice on it,
as a junior designer studying NFPA13 and other codes, I feel many concepts and subsections I understood wrongly!
Please review my question and help me


The project is : Ground+4parking typical floors + 18 residential apartments floors,
all main services rooms located in the ground floor and commercial shops
I have considered the parking 4th floor as the most demanding area for flow rate as it's OH-2 in my local code,
number of 12 sprinklers I've considered in the 1500 sq.ft
and the most remote area required residual pressure in the apartments top most floor 18th, and its LH residential sprinklers,
my concern is do I have to make 2 separate hydraulic calculation for each hazard and consider from both the highest flow and residual pressure required?

in this attached photo is the most remote sprinkler from the pump, upper top right corner , tis in chapter 11 (2016ed) shall be residential special design
approach correct? residential sprinkler in high rise building apartment
I'm going to consider 8 sprinkler head as attached photo in my hydraulic calculation?

I hope u will get what I'm trying to say
there is also automatic wet standpipe, i have 3 risers in this building, any way my pump flow will be 1000 GPM that will serve sprinklers as well
but I want to know if my concept is correct or not?

your answer will be appreciated,

 

[SprinklerDesigner2]

Just because something is farthest away does not make it the hydraulically most remote area.

Being it is a 14 story building at a minimum you will have 14 most remote areas because you do have at least 14 sprinkler systems. By definition each floor control valve is considered a sprinkler system.

I assume the parking garage is OH-2 per local code but since you mentioned 1,500 sq ft if you use quick response sprinklers you can shrink this area down to as low as 900 sq ft depending on the height of the ceiling.

For the residential you occupancies you can use residential sprinklers which means you will four heads per living unit and the density you need will be .10 gpm. Per listing a residential sprinkler per NFPA #13R needs a density of .05 gpm so in a room of 196 sq ft, assuming the room measures 14'x14', all you need is maybe 9.8 gpm but when you use residential sprinklers in a system per NFPA #13 you need the density of .10 gpm the sprinkler will have to discharge 19.6 gpm.

The discharge will be either per listing of the head OR a density of .10 gpm whichever is more.

 

[Aikah-Eng]

SprinklerDesigner2!! Thanks for your replay ^^
and that was a very important point thu about floor control valve,
I always consider the whole building having one sprinkler system, but is there any different if one system or multiple systems since all inside the building and it will be fed by one riser?
our local code in UAE forcing to install floor control valve in each floor even if 2 story building! more requirement than 13

since you mention this point I have one question here if you please,
if I have in one floor suppose 60k sq. ft. then I divide it to 2 sprinkler zone like 30k & 30k , should I have 2 risers for each zone or one riser can be used for both?
i know one riser can feed vertically each floor, but what about horizontally? it can feed to sprinkler zones?

the drawing showing used SSU in the parking 175 F - 79c (or it can be reduced to 900 since the Hight below 20ft) and Residential Spr in the apartments ..
so the most demanding area sure the parking OH-2 for flow rate.. but for the pressure I will finish my calculation for both and see

for the residential design area as per NFPA13, four head per 0.1 gpm/ft2 and I will increase to eight in having combatable concealed space, correct?
maybe I missed something

I think highest pressure will be in the apartments since the static will be high even if the parking OH-2..
I will finish the calculation by today in different area to most demanding pressure

Thanks

 

[SprinklerDesigner2]

With a 22 story building you will have a minimum of 22 systems and more if a floor exceeds 52,000 sq ft. One way to look at it is you will have a minimum of 22 risers as each floor control valve will be a "riser".

Just because it says "Riser" does not mean it has to be vertical. Who ever said a riser couldn't be horizontal?

So, with 22 systems you will end up with a minimum of 22 sets of hydraulic calculations but I have no doubt that minimum will grow. It wouldn't surprise me if you ended up with 40 or more sets of calculations.

Just a question, did I understand it correctly that you have a 22 story building with combustible concealed spaces?

 

[UFT12]

My considerations...

No matter what is the dimensioning schemes and geometry of your systems you should run individual calculations to be sure what is your most remote area. That is especially true between different hazard systems as each one will have to be dimensioned differently for an optimum design.

You shouldn't be concern about how many calculations you need to run. Run as many as you need in order to be sure that your water supply can provide the required demand to the entire system. This can be cumbersome and costs time sometimes but there is not other way. Experience will show you easier next time what areas you need to be concentrated mostly on. So make a graph with your water supply, x mark all your demands regardless if at the end you may be presenting only one demand. There are cases, however, this process may be easier. Repetitive systems that change only in elevation, typically found in apartment buildings show clearly what would be the most demanding area, so calculating all floors may not be necessary.

As far as concern grouping of systems in a building, assuming application of NFPA 13 here, section 4.5.1 states "the maximum floor area on any one floor.. This is a requirement that deals with maintenance of the system. If you need to take it down, take only a portion of it, not all of it. This is accomplished by sectional control valve assemblies, so that means you could potentially cover as many floors as you like provided they do not exceed the area limitation per NFPA 13. So practically, one riser equipped with a main control valve and an alarm valve can theoretically cover an unlimited number of floors. Since the wording clearly refers to "... each one floor...", you cannot do the same on the same floor (well maybe if you have fire separation). The same applies for floors which are not fire separated to each other. The floor area of these will have to be summed up against the area limitation of NFPA 13.

 

[Aikah-Eng]

yeah the building is 22 stories and all our construction materials in concrete,
most of the building ceiling is horizontal or smooth with no combustible concealed spaces
for the warehouses it's 90% noncombustible obstructed only

the system type is 100% wet only, after all there is no that much professional sprinkler system designers...

for the riser definition, yeah it can be either horizontal or vertical, it's also mentioned clearly in the handbook, but also in the handbook 2016, "Exhibit 8.1 manifold riser arrangement consisting of two wet pipe systems and one dry" , "where multiple risers are necessary to meet the area limitation , a manifold riser arraignment can be considered only in LH & OH
this riser shown in the vertical orientation, so I thought each system zone per floor should have separate riser with alarm valve as well .. but as said it's wrong it can be horizontally as per the riser definition

so I shall perform 22 HC to know the most demanding area, but for the 18 residential floors, it's all typical thu.. and the static pressure in the 18th will be the highest
I was about to make one calculation for the OH-2 in the 4th parking , and separate one for the LH from the 18th floor ..that's surprise me to make maybe more than 22 calculation

I'll do make calculation for each sprinkler system to make sure for the most demanding area

thanks

 

[Aikah-Eng]

UFT12

Thanks for your discussion, it's useful
before I understood I should run more than more calculation to know the most demanding area if I have multiple hazard in the same building
but for the same hazard like LH and typical floors ..it's not clear the most remote area will be the most demanding? spacing and all is same
static pressure will the highest in the most remote area …. to be sure I'm going to make calculations for all 22 systems

and I'll do the same for any future building even if it's the same hazard calcification

I do believe the area limitations per each system and the riser definition made confusion for lot of designers!! even some designer teaching in training centers
they have misconception !!
I was lucky to find this forum to clear this misunderstanding,

Thanks