Concealed Sprinkler Limits When in Beams?

2/27/2020

Per NFPA 13D 2019 Edition Section 8.2.1.3, "Concealed Sprinklers shall be permitted to be installed in beams not greater than 4 in. (100mm) in depth."

Semi-recessed heads can be permitted to be installed in beams up to 14in.

Why do concealed sprinklers installed in beamed applications have a 4 inch limitation?

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3 Comments

Franck

2/27/2020 12:29:12 pm

Best guess (not sure it is the exact reason)

With concealed sprinklers you need to get rid of the plate before the head actuate. The farther they are from the ceiling, the longer it will take and the more chance you will have to open additional sprinklers before the water from the ones above the fire start to control the fire.

With semi-recessed sprinkler, the fusible element is not « hidden » by a plate and should activate quicker

You will then have some limitations because the greater the distance from ceiling, the greater the response time (for normal sprinklers with unobstructed ceiling, the max distance is 12 in).
You can have a bit more than that, but not up to the max distance for obstructed ceiling as your sprinkler is below the beam and not in the « air pocket » between the beams

But this is « best guess » and somebody else may have a better explanation

Jonathan Joseph

2/27/2020 01:51:13 pm

My interpretation is.... For concealed sprinklers will have a delay in reaction time due to the heat or smoke passing through the vents of the concealed sprinkler. And if position lower it cannot collect the heat as quickly as pendent sprinklers.

I wonder if sprinkler companies are going to design a specific concealed beam sprinkler for this new code.

Karthik-india

3/6/2020 10:45:40 am

The exact reason is 300mm or 12inch from the bottom of true ceiling ,the fume or heat generated will be more at these space.

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Concealed Sprinkler Limits When in Beams?

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