Ordinary Temp. Sprinklers Adjacent to Diffuser?

2/14/2020

Are others experiencing AHJ's requiring that sprinklers placed in ceiling tiles directly adjacent to HVAC ceiling tile diffusers either be moved to at least 2'-6" away or replaced with intermediate-temperature rated sprinklers?

I am primarily referring to the vane style horizontal discharge diffusers you see in almost every office building, typically with an ordinary-temperature rated sprinkler in the center of an adjacent tile, only 1 ft. away.

Referencing NFPA 13, 2019 Edition, A.8.3.2.5: A diffuser in ceiling sheathing labeled by the manufacturer as "horizontal discharge" has directional vanes to move air further along the ceiling, and sprinklers located within the 2 ft. 6 in. (750 mm) radius should have an intermediate-temperature rating.

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9 Comments

Bruce Seiler

2/14/2020 10:32:54 am

If the maximum air being discharged from the supply diffuser is not greater than 100 F, you don't have to consider the distance to the sprinkler head. This requirement only applies when the normal air being discharged exceeds 100 F.

Sean

2/14/2020 11:00:03 am

Note the language in the code "should".

Lee

2/14/2020 11:14:49 am

The 100-degree threshold on 8.3.2.5(9) (in the 2016) is in reference to proximity to ducts. In my opinion, the direction of Table 8.3.2.5(a) stands, as reinforced by the Annex commentary. A proposal to the NFPA Committee was specifically presented to consider horizontal-discharge ceiling diffusers as downward-discharging, but that proposal was rejected. I just make them all intermediate-temperature throughout (I personally like the 175 over the 200), as allowed in NFPA #13.

Jon Sullivan

2/14/2020 11:41:00 am

I had an inspector flag this recently.

NFPA 13-19 9.4.2.5 states, unless high-temp sprinklers are provided throughout the compartment you need to comply with their provisions for providing other than ordinary temperature sprinklers.

In this case if you are within 2'-6" of a horizontal diffuser at the same plane, the sprinklers should be intermediate.

Lee's approach is good, prevents any accidental ordinary temp installation where not allowed.

I'd also engage your HVAC contractor/designer early. Typically 2'-6" is only one and a half tiles over, and it is easy coordination.

Lee

2/14/2020 12:01:48 pm

I know it is arguable, in terms of ceiling temperature, but in my opinion that is the correct path, or the Committee wouldn’t have rejected calling them downward-discharging. (According to Russ Fleming in NFSA Tech Notes #212, June 14, 2011, it was Proposal 13-127 in the 2009 Revision Cycle, and public comment period resulted in A.8.3.2.5.) I have also been told that while the HVAC system may not be designed to discharge higher than 100-degrees F, there are conditions where it could. I make them all intermediate, since diffusers could shift location in the field, so my drawings may not remain correct, and I don’t want my fitter having to stay on top of it. If there’s solid argument in the other direction, I’d sure be open to it.

Wayne Ammons

2/14/2020 01:31:33 pm

I probably could have been a little more clear when I submitted this question. It was not for interpretation of the standard, but to get a sense of whether or not others across the industry are running into this particular matter and how it is being addressed. In this particular case, the HVAC engineer confirmed that the RTU's are expected to reach temperatures of up to 115°F while in heating mode. The standard allows the use of ordinary or intermediate-temperature rated sprinklers throughout buildings, so I agree with Lee, the decision to go ahead and install intermediate-temperature rated sprinklers throughout an office building seems the safest bet, otherwise there would have to be some extra effort put into confirming HVAC output temperatures and/or coordination to ensure the required distances are met. Hopefully, over the life of the building as modifications are made and add/relocates occur, other companies are aware of the reasoning behind all the yellow or green bulbs and don't arbitrarily put in red...

Jon Sullivan

2/18/2020 09:39:58 am

To the HVAC system comment. Currently, you'll see HVAC designs limiting the heating discharge temperature to +15F over space temperature. The logic behind this is to promote better ventilation by reducing air stratification. By keeping the temperature within this range the code also allows you to reduce the ventilation rate, which on a cold day could add up to some nice energy savings. However, with the closer air/room temperature difference, more air is needed to heat, so maybe it's a wash.

Jessica Lutz

2/24/2020 01:29:11 pm

A common practice nowadays is to install Intermediate temp. heads throughout.

NFPA 13 allows this with restrictions...check with your AHJ first.

Joshua

3/8/2020 05:41:24 pm

My take as an HVAC Engineer and FP designer. If the heating is electric resistance then the discharge can be designed for less than 100 degrees, generally with ease. So I coordinate that my HVAC engineer provide around 90 degrees and then I can use ordinary temperature sprinklers. Near 100 degree designs waste heating energy because the supply air stratifies and works slowly into the space for comfort.

If the heating is from hot water then a control valve could be stuck open and greater than 100 may develop though unintended, so there I use intermediate temperature rated sprinklers.

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