If I have an in-rack system that needs to be calculated with the ceiling system, does the ceiling system need to be positioned above the most demanding racking? This might result in neither individual component area used being the most demanding of their type. Or do I calculate the most demanding rack along with the most demanding ceiling? I drew a quick-and-dirty sketch of a warehouse with the most demanding rack in red, the most demanding ceiling area in green, and the water source in blue. If the two areas are not lined up, this goes against the assumption that only one fire is happening in the building at a time. I'm thinking that the two need to be averaged over each other to come up with the most demanding single area, even if the most demanding ceiling or rack are not involved.
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11 Comments
Brett
1/23/2025 06:52:57 am
When the in-racks are required to be balanced with the ceiling sprinklers, NFPA 13 requires one remote area for both the ceiling sprinklers and the in-rack sprinklers. See 25.12.1.4 from the 2019 edition.
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Anthony
1/23/2025 07:37:24 am
I'd agree it should be the same "fire area"
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OP
1/23/2025 08:09:16 am
This makes a lot of sense. Thanks!
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Dan Wilder
1/23/2025 07:47:32 am
When this has occurred, I have always performed the calcs over top of each other as this is the situation that a fire scenario would occur in.
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NK
1/23/2025 08:36:11 am
The visual shown is the most hydraulically demanding scenario that would allow for future flexibility if the owner/tenant ever wanted to move their racks, but what Dan said about the fire operating sprinklers in the racks and at the roof directly above is a reasonable remote area for proving a fire can be controlled for that particular rack.
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Michael W Russell
1/23/2025 08:55:46 am
Tbh, the green remote area is not correct to begin with. It needs to be rotated 90 deg. and pushed to the far right, assuming the riser is in the blue, lower-left corner.
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Glenn Berger
1/23/2025 08:58:45 am
The issue here is that both systems may be in operation at the same time and as such you need to calc the remote area that is above the racks. This is still considered one event, but requiring both systems to operate to control the fire.
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Jesse
1/23/2025 12:39:44 pm
While realistically, the fire sceanrio will involve the ceiling level AS and in-rack automatic sprinklers (IRAS) in the same area, I actually provide several calcs balanced to the point of connection. I'll calc ceiling and IRAS in the same area.
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Pete H
1/23/2025 01:28:16 pm
Congrats, you have multiple design areas. One should be the in racks with the ceiling sprinklers above it as per the in rack design requirements.
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Franck
1/23/2025 02:55:33 pm
It reminds me the good old time when we were still making hydraulic calculation by hand…
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Jack G
1/23/2025 06:17:47 pm
Basically perform each calculation separately and try to get each close as possible at point of connection so as to limit the overflow when you balance.
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