Sprinkler Offset from Light Measured Diagonally?

6/2/2022

I have a surface-mounted light fixture on the ceiling, and I have to have a sprinkler at least 12-inches away from it in order to clear it as an obstruction. The light fixture is rectangular in shape.

The question is, when doing all of the spacing and the sprinklers are not exactly next to the object, they will have an offset from one side, and another offset from the other (short) side of the light fixture.

Does the sprinkler distance from the object need to be measured diagonally?

Or is the measurement "aligned" with one (or all) sides of the light fixture?

I may be overthinking this, and hopefully am explaining it correctly. Just because I'm 1-foot from the long side I could still be 6 or 8-inches offset from the other side of the fixture. Any help is much appreciated.

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3 Comments

Alex

6/2/2022 06:24:38 am

Hi,

Sadly I do not believe I am fully understanding your question.

If you need to be 12 inches away from the light (as stated in the question), you should be able to place the sprinkler anywhere parallel with the side of the light 12 inches away. You shouldn't be measuring from the corner when working in plan view.

If you have say a 4' long, 4" wide, and 4" tall light that is hung from the ceiling, I used to treat this situation like a truss. Here, you will measure diagonally. Refer to NFPA 13 (2013) Figure 8.6.5.2.1(b).

I'm happy to assist more if you follow up on my reply below with more detail!

Alex

Anthony

6/2/2022 08:06:10 am

I agree with Alex here. Its the closes measurement to the obstruction not the least axial measurement.

Dan Wilder

6/2/2022 08:58:57 am

If you meet the spacing requirements for the obstruction based on the closest point (corner, long side, short side) and the obstruction remains the same depth across its entirety, then the location of the sprinkler is in compliance.

If the fixture started off 4" deep then increased to 12" deep (say in less than 1'), you would need to comply with the horizontal spacing vs the vertical depth at all points

Example (assuming a standard spray sprinkler) would be a 2' wide fixture that starts 4" deep, then increases to 12" deep (square/rectangle/circle...doesn't matter the shape) the part that is 4" deep allows a horizontal clearance of 1'-6" from the edge (so the sprinkler could be as close as 2'-6" from the center of the fixture) but the 12" deep portion of the fixture requires a horizontal clearance of 3'-6"..so the sprinkler would need to be 4'-6" away from the center of the fixture.

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Sprinkler Offset from Light Measured Diagonally?

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