Zone Control Allowed Downstream of Another?

8/1/2023

Can a zone control valve assembly be installed downstream of another zone control valve assembly?

If there is a fire in Zone A (the primary zone), Zone A's flow switch would activate.

If there is a fire in Zone B (the secondary zone), Zone A and B's flow switches would activate.

Not sure whether this is permitted under NFPA 13 or 72. Thanks in advance.

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20 Comments

Pete H

8/1/2023 06:50:57 am

My personal take based on nothing:

as long as zone a and zone b's total square footage is less than the maximum area for a single system as per NFPA 13 requirements (as zone b still would count as part of zone a for this), I take no issue with additional control within a system. I could see it as specifically good for buildings with "wings" or long dead end hallways.

CARLOS

8/2/2023 04:48:35 pm

But when you have to work on zone A, wouldn't that also shut off zone B? Shutting both systems down? I'm sorry but I don't agree with that set up. I believe 13 might say something against it and 25 too.

Anthony

8/1/2023 07:20:13 am

Adding to what Pete said: This happens all the time with smaller dry systems and pre-action systems off a wet system. I like to have a small butterball valve flow switch and test and drain for elevators. Kind of a mini system to keep everything isolated.

Chad

8/1/2023 07:21:34 am

As long as the controls and flows are supervised (and in the flow calcs if necessary) I cannot imagine why it would not be permitted.

Dan Wilder

8/1/2023 07:45:12 am

We do this often for individual levels of mezzanines in larger building footprints (13-22' 4.4.2, but this changes based on applicable year) and only when the primary system is wet.

It is also allowed within NFPA 13-22' Section 8.1.3.

In both cases, area limitations (as the math allows) are not exceeded.

Casey Milhorn

8/1/2023 08:18:01 am

I agree with everyone else and I don't know of anything not allowing it, other than than sqft limitation of NFPA 13 and your calculations. I've done it, and it has it's time and place, but as a rule I'm a fan of as few valves as possible to avoid the possibility of a closed valve (even when tampered, they get ignored sometimes). BUT, when you have trapped sections, a section prone to maintenance issues, etc, it has it's place. You just have to explain very clearly to the fire alarm guy that a signal in A means A, and a signal in A and B means just B... and program accordingly.

Glenn Berger

8/1/2023 08:24:44 am

The installation of flow series in series happens often in facilities. Easy examples are flow switches associated with elevator / elevator machine rooms and more recently with battery rooms.

Alex

8/1/2023 09:56:52 am

To echo others, yes, I believe its compliant and have done so myself before in the past.

Jesse

8/1/2023 10:21:27 am

Yep, we do this quite often. As long as both control valves are supervised and accounted for in the calculations (if relevant to the calcs), its shouldn't be a problem.

Franck

8/1/2023 02:37:03 pm

Yes, it is possible
And even recommended in the examples above or if you have an interlock on a machine to stop it when the sprinkler system operates (could be a rolling mill, broke pit for a paper machine, paint spray booth…) and you don’t want to stop the machine if the sprinkler on the main system is activated quite far away…
In addition, it could be wise to isolate the sprinkler system that has operated on this limited area (broke pit of a paper machine, for example) and keep the remaining of the building under active sprinkler protection.
Don’t forget to properly supervise these additional subdivision valves.

(note that this may normally not be allowed in some other countries standard, such as some European countries…).

James Evans

8/2/2023 08:36:30 am

I agree with what has been said for the most part. I do not agree with the area limitation stated in the 1st response. I believe that the area limitation is per system. If you look at this situation you have two separate systems. In this case you would have the first system acting as a bulk run for the second system. It is no different than the manifold supplying multiple risers.

The only difference between the manifold and this scenario is that both flow switches would activate.

If you have a light hazard wet system that covers 52,000 sq. ft. and then you have a dry system that drops off the end of that system that is ordinary hazard covering 40,000 sq. ft. you do not add those 2 areas together and say the system is covering 92,000 sq. ft.. Each system is considered as seperate.

I believe the area limitation is per riser or flow device.

Wes

8/2/2023 08:42:59 am

Oh that's a really good question. I had thought the area limitation was based upon the risk associated with having so much square footage tied to one point of failure (one valve).

NFPA 13 - 4.4.1 (2022): The maximum floor area on any one floor to be protected by sprinklers supplied by any one sprinkler system riser or combined system riser shall be as follows... 52,000 sqft for Light Hazard, etc.

A System Riser (defined term in 3.3.225) "contains a control valve, pressure gauge, drain, and waterflow alarm device".

So one riser cannot serve both a wet system (52,000 sqft) and a dry system (40,000 sqft) at the same time.

Now if the wet system is 32,000 sqft and the dry system is 20,000 sqft, I think that's fine, because it'd still be under the 52,000 sqft limitation.

James Evans

8/2/2023 09:36:21 am

I guess we need to know what they are defining as a "combined system riser" as you can see the term is singular not plural. I am not sure if one riser downstream of another riser is considered "combined" or is it considered 2 individual risers?

Wes

8/2/2023 09:47:32 am

That's a good question James. I've been so resolute on this for so long - but I'm not entirely sure.

It seems like that one upstream riser is 'serving' all 92,000 sqft because that much area is downstream of it - but is it considered two individual risers, or a combined riser?

Any loss prevention folks weigh in here? I had thought the system area limitations were mostly based upon risk tolerance for single points of failure/reliability.

Casey Milhorn

8/2/2023 10:28:16 am

So the area limitation conversation is always fun and lots of opinions about it. From what I understand, the sqft limitation was based on the old pipe scheduling method. The NFPA 13 Committee knew that some type of limitation was good for obvious reasons, and also practical as not to have ridiculously large pipe once you got back closer to the riser. So nothing very scientific about the limitations. I know there has been discussion about revisiting the system area limitations but I guess never a consensus on changing it, or what to change it to. I personally think keep it simple and limit it to 100,000 sqft per system no matter the hazard/occupancy type. That would equate to a lot of savings in bulk feed main, risers, and labor. NFPA 13 is still based on one fire event at a time, not multiple. I can't really think of any practical reason to limit size, other than the rare occasion of a system being down for maintenance. Of course you still have to hydraulically prove the systems and meet water delivery times on dry systems. It's definitely an interesting conversation.

Mark Harris

8/2/2023 03:10:43 pm

I agree with the comments about a single riser or control valve and the 52,000 (or less) max floor area. As NFPA 13 is written could see an issue with the added a 40,000 SF dry system since both would be out with the wet valve riser shut. But Casey brings up interesting point about the connection with old pipe schedules. Thanks for sharing that insight and may be time to up those floor area amounts.

Paint booth would be another scenario similar to special equipment comment from Franck.

But then with backflow preventers or underground valves with multiple risers we already have scenario where one valve shuts off multiple systems.

James Evans

8/2/2023 03:39:34 pm

I still believe that each riser (or riser manifold) can start an additional 52,000sq.ft. or 40,000 sq.ft. depending on the hazard. we always have systems where a single valve turns off multiple systems or a single riser controls multiple systems since we tend to drop off dry systems and per-action systems from wet systems. No where in NFPA 13 does it state that if you do this, then you are limited to a certain square footage. We have done many maxed out wet systems with large wet systems that drop off the end of the front grid main and then goes out to a large dry system covering an exterior dock. In this scenario nothing says that the two systems must be added together and not exceed a certain area. As long as the calculations show that it works it should be allowed.

As far as a single valve controlling a large area, just think of the main control valve on a standpipe system, or a backflow for an entire building, or the valve after a fire pump.

We are doing nothing different by chaining systems together. The only difference is that the alarm may show multiple flow switches activating.

Please if adding the systems areas is required by NFPA 13 please show me where it is stated.

James Art, FPE, Pleasanton, Ca

8/2/2023 04:32:37 pm

Wes 8/2/2023 08:42:59 am agrees with me, so he's obviously correct! (-:

The code gives a Maximum area subject to a single impairment,
so you CANNOT then add a 2nd area to that, and have more area, like 92K affected.
A 2nd INDEPENDENT source to feed another riser is called for.

Too many valves are generally a bad thing, more to go wrong.

But one common scene is the strip mall, or even a regular mall where it would allow tenant improvements for each tenant without affecting others,
if there was, say, a valve from a main to serve individual areas.

Often a good C16 will ask and add such a valve, so he can work on and test without affecting other tenants.
Needs valve supervision, add to plans and/or a sign at riser.
But often the original installer used a grid, so there is no such main.

Sometimes similar layout in office buildings or hospitals, esp,
when a main down a hall supplies different areas, tenants or departments.

A huge fire at the Roseville Galleria mall, in Northern Ca with $55 Million loss in 2010, was party due to having turned off a large area while remodeling a small area. And also turning off other systems too soon.
See
https://en.wikipedia.org/wiki/Westfield_Galleria_at_Roseville
But sorry, does not get much into the fire and why it was so large. old news?
----------------------------------------------------------
Soldiers' Complaint*: Nowadays the news shows the big fire, but we rarely find out the why, or what went wrong.
Few will tell at first, as there are too many lawyers, and later no one is very interested?

* a Soldier cab always complain, but it doesn't do any good!

James Evans

8/2/2023 05:07:02 pm

All of this conversation is good but no one has been able to show in the code where it states that if one system such as a dry system or even another wet system drops of a primary system, that those 2 areas have to be added together and not exceed the maximum area of a single system.

I have never seen an informal interpretation of this and as far as I know as long as those areas have their own risers and control valves and drains, they are considered their own system. We have never in the past added the areas of these systems together to indicate the overall area. Each has always been considered separately having their own system area.

Again if it is in the code I would like to know where. Everybodies opinions are great but there is no indication in the code as far as I can tell.

WES

8/2/2023 05:31:01 pm

Did some digging on this - I wasn't 100% sure myself. The questions you're asking are really good. Sorry to be bearer of bad news.

Here's what I found -

NFSA May 2013 under NFPA 13-2013, question:
" Can a dry pipe system for an ordinary hazard occupancy covering 10,000 sqft at the remote end of a building from the water supply be connected to a wet pipe system covering the rest of the building (also ordinary hazard), which is 45,000 sqft? "

Response: "No. The purpose of section 8.2.1 is to limit the amount of area that would be unprotected when a single valve is closed. For ordinary hazard occupancies, the intent is to make sure that when a single valve is closed, no more than 52,000 sqft of area per floor is taken out of service. In the situation that you have described, when the single valve on the wet pipe system is closed, it would take 55,000 sqft
of area out of service on a single floor, which would violate section 8.2.1.

One way to solve the problem would be to run a separate pipe out to the dry pipe system from the water supply entrance. That would be a significant amount of extra pipe, but it would satisfy the standard.

Another way to solve the problem would be to connect a dry-pipe system to a wet system, as long as the total area downstream of the wet system does not exceed 52,000 sqft. You could do this and save a great deal of pipe by splitting the portion of the building covered by the wet piping into two systems.
This would cause you to install an extra set of wet system equipment (check valve, control valve, alarm and drain) but would save on pipe. No physical barrier or wall would be required between the two portions of the wet system. "

Their online archives go to 2017 https://nfsa.org/tag/expert-of-the-day/, but the handbook has more - https://nfsa.org/eodhandbook/

They answered a similar question on the size restrictions - which came from Ordinary Hazard Pipe Schedule of 130 sqft per sprinkler, generally limited to 400 sprinklers, which is generally "cited as the basis of the maximum system size of 52,000 sqft". It was apparently carried over as a practical limit from the OH pipe schedule days.

Zone Control Allowed Downstream of Another?

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