We have a job that is a non-conditioned, pre-engineered metal building that serves as essentially a shipping hub for small parts.
There are approximately 34 roll back overhead doors, half on one side of the building, half on the other.
We live in an area where freezing happens every year, and the coldest temperature recorded during each year averages 4.6 degrees from 2021 to 1948.
The doors' tracks are installed at approximately 11'-0" AFF and the door opening is approximately 9'-6" tall. The doors are approximately 10' wide and equally spaced down the building in the 25' bays.
The sprinkler system inside the building will be a dry system due to the fact it is not a heated building but we will need sprinkler protection underneath the roll back doors. I think technically speaking the code would allow Option A; a single drop to feed two HSW heads with a 1" valve for drainage per 188.8.131.52.3.2 and 184.108.40.206.3.5 (2016 NFPA13).
But this would mean the owner is responsible for draining approximately 17 drains every year that are not even installed with drum drip assemblies, so tripping a system and/or yearly freeze ups could be a very real possibility.
Do you guys believe this would even technically be a code accepted method of protecting under these doors from a dry system in a building with no heat?
Or, Option B; run a line parallel to the exterior wall below the door, but above the door opening and do so with needing just two drum drips (one per side) which should decrease the odds of a freeze up and accidental system trips for the owner substantially in my opinion.
What do you guys think? Would option A even be allowed?
Is option B the clear winner (especially with the owner in mind) even though the materials would cost more?
I have attached a rough bluebeam sketch to help illustrate the two arrangements. Thank you.
3/10/2023 08:38:44 am
While not being from a freezing area..my thoughts:
3/10/2023 08:39:39 am
Both options meet the standard, but in my opinion, option B is better fire protection. I have used this option several
3/10/2023 08:56:04 am
The use of horizontal sidewalls would not be correct as that is not within their listing.
3/10/2023 09:04:31 am
Are there any heads listed for that specific under door on a drop orientation/application? Never considered that fact, I guess not?
3/10/2023 09:22:10 am
Any HSW with installation requirements stating "Per NFPA" is in compliance.
3/10/2023 09:31:06 am
Sidewalls are allowable for this application. A standard sprinkler does not need to be listed for an application it is designated to be fictional at per NFPA 13.
3/10/2023 10:06:20 am
You're a top contributor but this is unfortunately a very misleading comment. Can it be edited or deleted? 90% of protection under overhead doors is done with HSW and it's permitted by NFPA 13.
3/10/2023 11:33:28 am
I don't think he's misleading, perhaps its more nuanced, allow me to try and clarify....
3/10/2023 02:35:34 pm
I see your point.. but
3/13/2023 06:13:50 pm
I have reviewed the above references that have been mentioned above as do acknowledge that 10.3.2 does allow the use of sidewall sprinklers in this application. But if you look at the rest of 10.3, you can see that no guidance is given for this specific application in placement of sidewall sprinklers.
3/10/2023 09:01:06 am
From an AHJ perspective, I am concerned with downtime and prefer option A (with a nitrogen generator :) ) As long as its properly maintained I don't see freeze ups any more likely that the pipe being struck. Physical damage can occur all year, freeze ups only in colder times.
3/10/2023 09:40:07 am
My gut at a contract designer wants to go with option B as limiting drainage is a foundation of good design.
3/10/2023 09:31:25 am
You could combine both approaches by doing Option A and running a small (1/2" or 3/4") common drain line along the wall above the door opening and draining all of the Option A drops into it.
3/10/2023 09:37:24 am
I also am in the opinion of option A. Possibly with a smaller gang drain. Either way. the amount of water in the drop ,if pitched correct, should be a fairly easy run with a bucket for a man or two yearly. Be seems like more impact risk than necessary in those locations. Industry standard is A in my opinion.
3/10/2023 10:47:54 am
I'm in agreement with Connor. I have designed using variations of both methods, depending on how the rows of doors are arranged. I concur with the concerns others have mentioned, including potential for physical impact and, installing the drain down to an accessible level where it is less likely to be ignored. On the engineering side on the front side of a new project, I try to steer them away from roll-back doors, if physically possible.
3/10/2023 05:27:42 pm
Option C: Run the low branch line above the door tracks with a single drum drip where it tees off of the drop from the roof level system. Use Victaulic Vicflex model VS1 - dry sprinkler flexible hose assemblies to drop from the branch lines and sprinkler beneath the doors. They will run about $200 each. Be sure to add my consulting fee into the change order.
3/13/2023 08:40:24 am
I don't like option A. It looks like back to back sprinklers that would run against 220.127.116.11.4 (NFPA 13 2016)
3/13/2023 11:22:42 am
I think option B is best personally since it would reduce the # of drains significantly and give the drains a drum drip which will make draining the trapped water/condensation more practical for an owner. And with the amount of room between the door opening and the underside of the door the line should be high enough that impact risk should be minimal BUT everyone does make good points, especially the "damage happens all year, freezing only happens in the colder times". That's actually a very KISS perspective I think.
3/14/2023 01:52:42 pm
With option B you are technically turning it into a gridded system. Dry pipe systems cannot be gridded according to NFPA 13.
3/15/2023 11:00:58 am
It wouldn't be gridded if it has a single supply from the overhead and is a line fed from the middle in a "bull head tee' fashion.
3/16/2023 06:09:03 am
If you do go with option A, I have spec’s automatic drum drips in the past for garages with multiple zones (and low points). They will alert you when full and can automatically discharge the water using solenoid valves. They also come heated for areas of extremely cold temperatures.
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