Suspended acoustic baffle vs Sprinkler head 2

[MarsMax]

Hello gents,

I'm working on a office renovation project that involves a large number of suspended architectural acoustic flats/baffles installed in a meeting area.

Some details of the situation:

1. All flats will be installed on rails from a suspended ceiling system. Distance between suspended ceiling and higher ceiling is 15". (This distance could be changed to meet Code and will be on my call)
2. Each flat has a dimension of 1/2" thickness, 8" length, 24" to 66" ununiform depth.
3. Some pics for references:

I'm currently providing sprinkler heads only on primary (higher) ceiling. However, I'm worry about the sprinkler coverage will be compromised due to these numerous suspended flats.

Can anyone advise me on this?

Do I need to put/Can I put beneath sprinkler heads to flush with the bottom of the deepest flat (That will be (66"+15"=81") below the primary ceiling).

Thank you in advance.

 

[cdafd]

Not near a book

I know it is not egg crate but have you looked at that section?

Will there be 50 % opening??? With how they are laid out?

I take it these do not burn???

 

[UFT12]

What does the listing of the product suggest about fire sprinklers? Are these rigid or a kind of fabric or rubber that can sag or bend? And what is the distance between them?

 

[cdafd]

What is the distance between each row??

 

[cdafd]

Check this thread

https://www.eng-tips.com/viewthread.cfm?qid=340890

 

[MarsMax]

Thank you guys @cdafd, @ UFT12.

Some answers that I know:
1) The distance between each row is about 12". The total length of one row of suspended rail that these flats will lay-in is 180". Each row of rail will have 10-12 flats.
2) The flats are rigid and they achieved a Class A Flame Spread rating also passed CAN ULC S102-10.


I checked section 8.15.14 (NFPA-13, 2013) Open-Grid Ceiling and considered one section between two suspended rails as one "opening":

That said I have 9 x openings in total and each opening is 180" x 12". Openings constitute more than 70% of the suspended area.

The depth of each flat is 66" but the thickness is only 1/2". Section 8.15.14.(1) said "Open-grid ceilings in which the openings are 1/4" or larger in the least dimension, where the thickness (1/2" in my case) OR depth (66" in my case) of the material does not exceed the least dimension (12" in my case) of the opening".

So it seems I'm good here without beneath sprinkler heads? As long as the distance between my suspended rails and my primary ceiling satisfies with Section 8.15.14.(2), which is 18 in. for 10 ft x 10 ft sprinkler layout in light hazard.

 

[MarsMax]

One thing that I was really confused was:

If I have less than 18", for example 15", between suspended ceiling and primary ceiling, per Section 8.15.14, I will need to install beneath sprinkler heads.

Does that means I will need to bring down pipes to make some new pedant sprinkler heads flush with the bottom of the suspended ceiling system? That will be (66"+15"=81") below the primary ceiling.

However, Section 8.6.4.1 said "Under unobstructed construction, the distance between the sprinkler deflector and the ceiling shall be a minimum of 1" and a maximum of 12" throughout the area of coverage of the sprinkler". So, I should put new heads at 12" instead of flushing with the bottom of suspended ceiling??

 

[cdafd]

I am thinking you are good to go with sprinklers at the deck


I am not a designer or engineer
Just my opinion

Plus if installed at lower level, bottom of the things,,, I would say almost worthless, as they may never activate.

 

[UFT12]

If I have less than 18", for example 15", between suspended ceiling and primary ceiling, per Section 8.15.14, I will need to install beneath sprinkler heads.

Note that 8.15.14 mentions the distances between open grid ceiling and deflector, not bottom of upper ceiling. Therefore your needed clearance is most likely shorter than 15". Also, 8.15.14 does not tell you you need to install sprinklers underneath, it only tells you the requirements for open grid ceilings for adequate level of protection from the higher level sprinklers only. If this is to be considered as open grid ceiling you obviously do not meet all criteria but that does not mean you only have one option of installing low sprinklers. It also means you could talk this over with the architect to provide you the necessary clearances needed depending on the sprinkler in between distances and the classification of the hazard.

Speaking of hazard, I take it you do not talk for an extra hazard occupancy since in this case the 3 times rule is voided by these members too (see 8.6.5.2 and 8.6.5.2.1.4, although A.8.6.5.2.1.4 rings the bell for consideration for LH & OH too).

Therefore for me it would make sense to ask for better clearances.

 

[MarsMax]

Thank you!

 

[MarsMax]

Thanks for this very clear and thorough explanation @UFT12.

I understand what you said and the architect is most likely willing to provide me necessary clearance needed.

What I'm really confused now is, 8.6.4.1 requires 12" max. from the deflector to the ceiling. 8.15.14.1.(2) requires 18" min. from the deflector to open-grid ceiling.

Let's say right now I'm having 13" from the deflector to top of open-grid, and the grid itself is 66“ deep. If the architect does not provide me clearances, I will have to install low sprinklers. However, the distance between the deflector of my low sprinklers and the high ceiling will be close to(66"+13"= 79") which certainly exceeds the 12". So it seems I cannot install low sprinkler heads at all, and the only option that I can meet both clause 8.6.4.1 and 8.15.14.1.(2), is to provide 18" clearance from the deflector to open-grid.

Does this sound right to you?

Also just to confirm the space is light hazard.

Thanks,

 

[cdafd]

Terry

If just the grid was there, without the dangly thingys,,,

Do you think you would have a problem placing the sprinklers at the deck?????

 

[MarsMax]

Hi @cdafd,

That will be a typical open-grid without any problem I believe...

With those dangly things, I'm not thinking that my situation can be considered as open-grid ceiling now.. they are so deep and will interfere with the spray pattern. Also an issue about the heat & sprinkler activation.

 

[cdafd]

I think once you see it up there and matches the layouts you have posted

You may see it is not a problem calling it open

If 70% or better

 

[UFT12]

Let's say right now I'm having 13" from the deflector to top of open-grid, and the grid itself is 66“ deep. If the architect does not provide me clearances, I will have to install low sprinklers. However, the distance between the deflector of my low sprinklers and the high ceiling will be close to(66"+13"= 79") which certainly exceeds the 12". So it seems I cannot install low sprinkler heads at all, and the only option that I can meet both clause 8.6.4.1 and 8.15.14.1.(2), is to provide 18" clearance from the deflector to open-grid.

Does this sound right to you?

No. The clearance for the lower sprinklers is not measured from the high ceiling rather "their own" ceiling. If you need additional (low) sprinklers then you have an obstruction to the overhead system and that's your reference point.

 

[TravisMack]

My gut is this is a light / ordinary hazard area. The obstructions are <48" in width. They are suspended so the top is ±18" below the roof deck. They are suspended on some type of relatively small diameter hanger. It is protected with Standard spray, standard coverage sprinklers.

Based on all of this, you would be applying the criteria for the 3x rule. Then, in light / ordinary hazard areas, only structural members shall be considered for the 3x rule. These are not structural, so they basically go away as far as sprinkler protection is concerned.

That may be enough to get you providing sprinklers at the deck level only.

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

http://www.mfpdesign.com

 

[MarsMax]

Right, and it's more than 70% open. I'm now just cannot find a certain clause for this situation, to make me safe... Apparently these dangly things are not considered as open-grid (8.15.14) nor suspended vertical obstruction (8.6.5.2.2).

 

[MarsMax]

I see. Thank you @UFT12

 

[MarsMax]

Travis,

Sounds right. It's light hazard, and each suspended flat is 8 in. width. The top could be 18" below the higher T-bar ceiling. Sprinklers are at the higher ceiling. Sprinklers are standard spray, standard coverage sprinklers.

It just seems to me that they can still interfere with sprinkler spray pattern since they are are 66" deep... and I guess another concern is these deep flats below sprinklers, will affect the temperature of the sprinkler heads. Which in turn, will delay sprinkler reaction time.