Best Approach for Dry System & Overhead Doors?

3/10/2023

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 8.16.2.5.3.2 and 8.16.2.5.3.5 (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?

Option A:

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.

Option B:

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.

21 Comments

Dan Wilder

3/10/2023 08:38:44 am

While not being from a freezing area..my thoughts:

Tripping of a system due to draining of Aux drains - While the standard only requires a valve and plug, providing a second valve with a section of piping between would be in the best interest of your owner. This is not a drum drip but would act similarly to one for maintenance purposes.

Yearly freeze ups - this should not be a concern with pitched lines and return bends, what-if game aside.

Trips - Can't really put the what if game into this but proper ITM procedure by the owner should avoid this. A concern yes, but so is impact.

Option B with the single line across 17 doors + space between puts the average length at about 200'...x ½"/10' slope (this is a branch line in my book) is 10" of drop - 5" per side. The line will be low already and instead of 1 spot every ~25' of potential impact, there is now a continuous and increasing impact zone...

While I personally would propose option A with piping to the wall for ground level drainage capability, providing both options to the owner with your pros/cons should be the approach and let the owner decide. They can save some upfront money but will pay for it long term, or spend up front and save the long term.

On a side (and more expensive) note, AGF (I'm sure others) has a heated auxiliary drain cabinet with automatic draining option.

Barry

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

That said, Option B will cost more for the contractor and it is not unreasonable for them to ask for a CO for the better option unless it was specified at bid time.

There is a difference between cheaper and better value.

Glenn Berger

3/10/2023 08:56:04 am

The use of horizontal sidewalls would not be correct as that is not within their listing.

Not sure what the best solution to avoid problems that occur due to the trip testing of the dry pipe valves and trapped portions in the system..

Chad

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.

NFPA 13 - 2022

10.3.2 Sidewall Spray Sprinklers.
Sidewall sprinklers shall only be installed as follows:
(4)To protect areas below overhead doors

10.3.4.1.7
Where sidewall standard spray sprinklers are installed to protect areas below overhead doors within ordinary hazard occupancy spaces or rooms, protection area and maximum sprinkler spacing for light hazard as specified in Table 10.3.3.2.1 shall be permitted under the overhead doors.

11.3.2 Extended Coverage Sprinklers.
Extended coverage sprinklers shall only be installed as follows:
(8)Extended coverage sprinklers installed to protect areas below a single overhead door(s)

Anthony

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.

If the sprinkler was to be used outside of the proscribed standard applications, then it needs to be listed for special application.

NFPA 13-16:
8.4.2 Sidewall Spray Sprinklers. Sidewall sprinklers shall only
be installed as follows:
(3) To protect areas below overhead doors

8.7.3.1.7 Where sidewall standard spray sprinklers are in-stalled to protect areas below overhead doors within ordinary hazard occupancy spaces or rooms, protection area and maximum sprinkler spacing for light hazard as specified in Table8.7.2.2.1 shall be permitted under the overhead doors.

danefre

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.

chad

3/10/2023 11:33:28 am

I don't think he's misleading, perhaps its more nuanced, allow me to try and clarify....

UL doesn't list HSW's for under door coverage (which sounds obvious now that I say it out loud, its not on a wall.

But NFPA 13 permits its use for it.

3/10/2023 02:35:34 pm

I see your point.. but

The statement: "the use of horizontal sidewalls would not be correct" is misleading. Especially since it's the most common solution to protect under overhead doors.

A listed sidewall would be cULus listed for installation in accordance with the latest edition of NFPA 13, which includes protection under overhead doors. IMO it's a bit unreasonable to expect a testing laboratory to cover every situation that's covered by NFPA 13.

The Reliable MBEC-14 CMSA sidewall is good example of a sidewall not mounted on a wall.

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.

Option B, IMO, will lead to more inadvertent physical damage and thus longer downtime as repairs in industrial facilities (low occupant count) are lower priority that R occupancies for contractors when they are busy. If you went with B, adding a supervised control valve to segregate that line could mitigate this somewhat if they can quickly send a tech to reset the valve and do the repairs later.

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.

However, I, like many of you, have seen more than one sprinkler ripped apart by a forklift. So, option A is probably the winner. I agree with Chad here, limit your options for mechanical damage.

I know that 17 drains are a lot. I think you'll pay for those 17 drains by not having to replace that line.

Connor

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.

This would mitigate the risk of damage by putting the drain piping out of the way, and you could terminate the drain at a drum drip in a heated cabinet. Due to the required pitch, you may need a few drum drips to keep from dropping below the doorway. This piping would need to be accounted for in the system volume, but since it is drain piping only it does not need to be a minimum size.

Brad K

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.

Dave

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.
How about Victaulic VS1 SW's, lol.

Pete D.

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.

Pete H

3/13/2023 08:40:24 am

I don't like option A. It looks like back to back sprinklers that would run against 8.7.3.1.4 (NFPA 13 2016)

Chris

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.

Jay

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.

Alex

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.

If you do use them, coordinate with electrical and get ready for the fee! But it’ll avoid maintenance down the road.

Best Approach for Dry System & Overhead Doors?

Leave a Reply.

ALL-ACCESS

SUBSCRIBE

COMMUNITY

YOUR POST

PE EXAM

FILTERS

ARCHIVES

PE PREP SERIES