Two supply per floor sprinkler doubts

[DavidCR]

Hi folks, I go again with a long one.

I have a high rise building with a combined system. With two risers fed by a pump at the basement,please see attached drawing.

I´ve come across with this question previously but I see it needed a diagram and an update, so here I go again with this matter that is giving me some headaches.We are supposed to follow NFPA 101 and this is a high rise office building.

My company is buying this building under construction and they want to know if the fire system is ok, so they are asking my criteria on several points. I have my thoughts, but I´d like to hear your comments.

The risers are interconnected on each floor, with identical arrays on each side, they use 4" pressure reducing valves (Wilkins Zurn ZW109FP) this valves isolate the interconnection from the feeders and controls pressure for both sprinklers and hoses.

Question 1. Two flow alarms.
As there are flow detectors at both supplies on each floor, is this Ok?. I mean, when a sprinkler opens, you don´t know which one of the two flow sensors opens, or it may sense half the flow on each sensor, or it may not activate the detector due to the low flow (???).
I see that the alarm panel actually sound with the test device, but you only know it was on a floor but you don´t know if from the west o east side of the floor. The builder states that when opening the test connection on the test device located at the riser, it works, and that is all.

Quetion 2. Reated to the previous. Is it required to install a test connection at each side of the building on each floor. The builder says that he will install a test connection on the most hydraulic remote point at the highest floor and that is all.

Question 3.Check valves on sprinkler risers.
I´m not sure if per NFPA 24 it is required to install checks to prevent circulation. There are no check valves but the Wilkins pressure reducing valves. Do you know if the pressure reducing valves can be considered as check valves to prevent circulation (counter flow on the valve) or riser to get emptied on tests? Or is it required to install additional checks?.

Question 4. Pressure reducing valve flow range.
They decided to install the pressure reducing valve due to the local requirement of 85psi max for hoses, but they connected it so it also reduces pressure for both hoses and sprinklers (no real need, but the designer comments it works as an extra security to avoid unnecessarily high pressure on sprinklers).

Since the pressure reducing valve is 4" it is supposed that it has a limited working flow range (non pulsating), and I doubt it will work fine for the flow of one sprinkler. Is it Ok to use a pressure reducing valve like this for sprinklers? I mean how do you know it will work fine if one or two sprinklers open. Am I worrying for something that is not an issue for other reason?

Other valve manufacturers state that a 4" pressure reducing valve will work fine for a flow range from 70 to 300 gpms for example, and if you need lower flows, you will need a smaller valve installed on parallel, that goes down to the little flow. Wilkins data sheet does not mentions a lower limit, just an advivce on low velocities and consulting their experts (they havent answered yet).

The designer states that the design is OK, but the people buying the building is afraid to meet problems later if there is a code problem or bad design. Our local AHJ does not give a strong opinion on this design matters, and I want to give a good advice on this if possible.

Any input is highly appreciated.

 

[SprinklerDesigner2]

I believe you are fine.

NFPA 14 "Standard for the Installation of Standpipe, Private Hydrant, and Hose Systems" - 2000 Edition

4-2.8.3 Where sprinkler system piping supplied by a combined system is supplied by more than one standpipe (“loop” or “dual feed” design), a sign shall be located at each dual or multiple feed connection to the combination system standpipe to indicate that in order to isolate the sprinkler system served by the control valve, an additional control valve or valves at other standpipes shall be shut off. The sign also shall identify the location of the additional control valves.

 

[cdafd]

Question 1. Two flow alarm
depending on the fire alarm panel used,
1. you can set it up to let you know say 2nd floor east side or 2nd floor west side
2. eliminate one and just set it up per floor
3. may not really matter, because once a head pops both will set the fire alarm off.
4. you will also more than likely have one in the pump room, so that will set the fire alarm system off.

Quetion 2. Reated to the previous. Is it required to install a test connection at each side of the building on each floor. The builder says that he will install a test connection on the most hydraulic remote point at the highest floor and that is all.

will have to check nfpa 13, but pretty sure you need an inspector test for each flow switch at/ near flow switch.

besides the builder does not know what he is doing, if he does one at most remote, it will not test the one on say the second floor!!!!!!!!!!!!!!

Question 3.Check valves on sprinkler risers.

not sure the question, I mean say you had a 3 story building and the floors were interconnected, you do not need any check valves.

Question 4. Pressure reducing valve flow range.

have not fought fire in a long time so I do not know what nozzle pressure is needed, but limiting it to 85 psi does not seem correct????

how long is the building form one stair to the other?????



highly suggest you talk to the spinkler company first with your question/ concerns, and see what they tell you.


if they do not sound like they know what theyh are doing hire a fire protection engineer to evaluate the design!!!!!!!!!!

 

[TravisMack]

Ok, I will try to take a stab at this one:

"Question 1. Two flow alarms.
As there are flow detectors at both supplies on each floor, is this Ok?. I mean, when a sprinkler opens, you don´t know which one of the two flow sensors opens, or it may sense half the flow on each sensor, or it may not activate the detector due to the low flow (???).
I see that the alarm panel actually sound with the test device, but you only know it was on a floor but you don´t know if from the west o east side of the floor. The builder states that when opening the test connection on the test device located at the riser, it works, and that is all."

Assuming this floor is less than the allowable maximum for a single system, the flow switch is there to sound an alarm and alert the general area. So, if the flow switch trips, you will know what floor at the alarm panel. You will likely have smoke detectors that can be more precise, but I don't see a problem with this arrangement. After all, if you only had 1 flow switch for the floor, you wouldn't know east or west, just the floor, same as you will now.

Question 2. Related to the previous. Is it required to install a test connection at each side of the building on each floor. The builder says that he will install a test connection on the most hydraulic remote point at the highest floor and that is all.

You are required to test each flow switch. How is he going to test each flow switch on each floor if you have only one test connection at the top floor. You could use 1 test connection on each floor to trip the flow switch to make sure it works. That should not be a problem. But, one at the top floor only is not going to suffice.

Question 3.Check valves on sprinkler risers.
I´m not sure if per NFPA 24 it is required to install checks to prevent circulation. There are no check valves but the Wilkins pressure reducing valves. Do you know if the pressure reducing valves can be considered as check valves to prevent circulation (counter flow on the valve) or riser to get emptied on tests? Or is it required to install additional checks?.

Per NFPA 14, you are required to have a check valve at each location where the sprinkler system connects to a combined standpipe:
6.3.5* Control Valves and Check Valves on Combined
(Standpipe/Sprinkler) Systems.
6.3.5.1 Each connection from a standpipe that is part of a combined system to a sprinkler system shall have an individual control valve and check valve of the same size as the connection.
6.3.5.2 A listed pressure-regulating device that prevents backflow shall be considered a check valve, and an additional check valve shall not be required.
The valves you have indicated are pilot operated pressure reducing valves. I am not positive, but I don't believe they are listed to serve as check valves as well. I am not 100% sure of this, so you should check further with the manufacturer.

Question 4. Pressure reducing valve flow range.
They decided to install the pressure reducing valve due to the local requirement of 85psi max for hoses, but they connected it so it also reduces pressure for both hoses and sprinklers (no real need, but the designer comments it works as an extra security to avoid unnecessarily high pressure on sprinklers).

I know the Tyco PRV is capable of working with very low flows. However, in the past, when we have put a 4" PRV like you show, we also put a 2½" PRV in parallel to handle the flows should only 1 sprinkler operate. Typically, the flow range of those larger PRVs do not go low enough for a single sprinkler flowing.

Also, it is likely the pipe and fittings are already listed for 300 psi. The only concern would be the heads. It is not uncommon to use 300 psi heads in these situations and use the full pressures to decrease the pipe sizing. But, you already have small sizing, so that may not be an issue.

After looking further at the data sheet, it says the minimum flow rate is 1 ft / sec. That equates to about 40 gpm for a 4" Sch 40 pipe. So, I would bet that it is not going to be suitable for flows <40 gpm. Again, a talk with the manufacturer's tech services would be warranted here.

One other thing that I noticed missing from your diagram is the 3" drain riser in each stairwell.
7.11* Drains and Test Riser.
7.11.1 A permanently installed drain riser shall be provided adjacent to each standpipe equipped with pressure-regulating devices to facilitate tests of each device. The drain shall be sized large enough to handle the full flow required from the largest pressure-regulating device but shall not be less than the following:
(1) The size of the discharge outlet of the pressure-regulating device for devices that are greater than 21?2 in. (65 mm) in size
(2) 3 in. (80 mm) to facilitate testing of 21?2 in. (65 mm)pressure-regulating devices
(3) 2 in. (50 mm) to facilitate testing of 11?2 in. (40 mm)
pressure-regulating devices

So, my gut says to not be overly concerned about the flow switches, just make sure you have a way to test each of them. I would want to check further into the check valve situation and possibly require a 2½" in parallel as 1 gpm for 2½" sch 40 is 15 gpm, which equals +/- 7 psi for a 5.6k sprinkler.

Good luck with the project.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[cdafd]

TravisMack

I took my stab

""Assuming this floor is less than the allowable maximum for a single system, the flow switch is there to sound an alarm and alert the general area. So, if the flow switch trips, you will know what floor at the alarm panel. You will likely have smoke detectors that can be more precise, but I don't see a problem with this arrangement. After all, if you only had 1 flow switch for the floor, you wouldn't know east or west, just the floor, same as you will now.""""


say with this setup that is proposed, and say we are talking 2nd floor only

1. say you had 100 feet run of pipe from west feed to east feed.
2. so say a sprinkler head right in the middle pops.
3. that head is fed from both sides, right?
4. so if you had a flow switch on one floor control valve only, say on the west side.

5. when the head pops,even though you are getting feed from the east side you will get flow from the at the same time from the west side
6. so the flow switch will activate no matter what!!!!!!!!!!




""""You are required to test each flow switch. How is he going to test each flow switch on each floor if you have only one test connection at the top floor. You could use 1 test connection on each floor to trip the flow switch to make sure it works. That should not be a problem. But, one at the top floor only is not going to suffice."""


agree with only needing one.

The problem is once again if you have two flow switches on the same floor, tied into the same problem

they will both go off roughly the same time

so unless at the fire alarm panel you designate say 2nd flr west flow and 2nd flr est flow switch, you will not know which one went off.

That is why I say you only need one per floor, and you save money from this also.


Per NFPA 14, you are required to have a check valve at each location where the sprinkler system connects to a combined standpipe:6.3.5* Control Valves and Check Valves on Combined(Standpipe/Sprinkler) Systems.6.3.5.1 Each connection from a standpipe that is part of a combined system to a sprinkler system shall have an individual control valve and check valve of the same size as the connection.6.3.5.2 A listed pressure-regulating device that prevents backflow shall be considered a check valve, and an additional check valve shall not be required.The valves you have indicated are pilot operated pressure reducing valves. I am not positive, but I don't believe they are listed to serve as check valves as well. I am not 100% sure of this, so you should check further with the manufacturer.""""



sounds good to me


question 4

still question the 85 psi limit

didn't someone have a high rise fire in PA and there was trouble with not enough pressure to the nozzles????
""""

 

[DavidCR]

Thanks a lot for the comments by now.

By the way, this is 16 floor building. See the photo of the actual riser on each stair.

Travis.
On question 3.
Following 6.3.5.1 mentioned, the check looks to be req. for the sprinklers not for the hoses, but in the actual situation it is upstream the sprinklers and hoses. So I think an additional check valve is needed for only the sprinklers. ???

On question 4.
I´m waiting for Wilkins response.
Travis.I was not aware of the drain riser req. So if the PRV is 4" the drain riser according to 7.11.1 (1) you mention should be 4". There is PVC drain riser but it is not the size of the PRV.

Cdafd. About the pressure limit. I agree with you. Fire dept that is our AHJ is this issues, is not very clear on this, they adopt NFPA but they are very worried about high pressures, and this is a confusing issue sometimes. The stairs are separated about 25m (82').

 

[cdafd]

Cdafd. About the pressure limit. I agree with you. Fire dept that is our AHJ is this issues, is not very clear on this, they adopt NFPA but they are very worried about high pressures, and this is a confusing issue sometimes. The stairs are separated about 25m (82').


was wondering about the length to fiqure friction loss in the hoses

have not had to squirt water in a long time, so do not know waht the minimum pressure is required to drive a nozzle, I should know, nut we do not build over three stories, so not an issue.

 

[cdafd]

have not read this:::

and it is from 1996

http://www.usfa.dhs.gov/downloads/pdf/publications/tr-082.pdf

 

[cdafd]

Standpipe System and Improperly installed standpipe valves Pressure Reducing Valves (PRVs) provided inadequate pressure for fire department hose streams using 1 3/4-inch hose and automatic fog nozzles. Pressure reducing valves were installed to limit standpipe outlet discharge pressures to safe levels. The PRVs were set too low to produce effective hose streams; tools and expertise to adjust the valve settings did not become available until too late.

http://911research.wtc7.net/cache/wtc/analysis/compare/iklim_meridienplaza.html

 

[cdafd]

seems like minimum pressure at teh nozzle tip is anywhere from 50 psi on up, depending on the nozzle.


so if you ad friction loss or the hose

and friction loss for elevation, will 85 psi get it??

http://www.akronbrass.com/uploadedFiles/Products/Nozzles/Low_Pressure_Nozzles.pdf

 

[TravisMack]

My bad on the drain riser size. We typically use 2½" PRVs so the drain riser would be 3". With the 4" PRV, you are correct, it would be 4". You have to be able to test these PRVs at full flows. The 2" main drain from the sprinkler floor main drain is not going to cut it. That is the purpose of the large drain.

You could fix the check valve issue by putting a check valve after the system control valve, just above the grooved reducer.

Many of these pilot operated PRVs also require a ½" pressure relief valve downstream of the them. Check the data sheet for that, but you may need to have change the test-n-drain device to one that has a pressure relief valve on it. I believe these valves also require a pressure gauge on the supply side of the valve. I didn't notice one in the picture. You need a supply side gauge as well. That could be tapped on the standpipe if you can't get it installed anywhere else.

and friction loss for elevation, will 85 psi get it??

The 85 psi is set at the discharge of the Wilkins PRV,so there isn't any real elevation to consider. Maybe 3-4'. If you only need 50 psi at the nozzle, then you have +/- 35 psi to lose as friction losses in the hose.


I hope that helps.


Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[cdafd]

""The 85 psi is set at the discharge of the Wilkins PRV,so there isn't any real elevation to consider"""

You are correct, I thought about that after I posted.

But also if they connect at the 1/2 landing below the floor they are attacking do you lose 2 1/2 psi ????

 

[Cidona]

I wouldn't think you need the additional check valves. My understanding is the purpose of these is to reduce drain time and the negative effects of introducing fresh oxygen into the piping any more than needed when needing to change out a FHV and preventing the need for someone to run around all the floors shutting on and off all the indivigual systems during the drain and fill of servicing the system. Your arrangement accomadates this. The only disadvantage of the current set up is that if the PRV is being worked on, then the FHVs are also out on that level (on that side). Installing a check after the sprinkler control valve wouldn't seem to help that situation, but again probably not needed anyway.

 

[TravisMack]

Cidona:

How do you reconcile that with the requirements of NFPA 14?

6.3.5.1 Each connection from a standpipe that is part of a combined system to a sprinkler system shall have an individual control valve and check valve of the same size as the connection.

Pretty much says you have to do it right there. I don't believe the pilot operated PRVs are not listed as check valves as well.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[ryano669]

From 14, 2010:

6.3.5.2 A listed pressure-regulating device that prevents backflow shall be considered a check valve, and an additional check valve shall not be required.

I'm not saying the Wilkins is capable of preventing backflow, but that may have been the logic behind the design.

I agree that the 4" PRV is too large to operate with just one sprinkler activating, as has already been posted. We usually provide a 2½" PRV for the floor control valve, and use pressure reducing hose valves attached directly to the standpipe.

 

[TravisMack]

Ryan:

I agree that if the Wilkins is capable of preventing backflow then they don't need another check. I just didnt' see in the datasheet where it indicated that. I know the data sheets for the 2½" hose / sprinkler control valves say that. It just requires a call to the manufacturer.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[ryano669]

Sorry Travis, I just read your earlier post about where you quoted 6.3.5.2.

 

[cdafd]

Is the check valve built into the floor control assembly???????

http://www.tpub.com/content/UFC2/ufc_3_600_01/ufc_3_600_010045.htm

 

[Cidona]

Em, I may have jumped the gun there. I was thinking that the PRV was going to act as the check but after reviewing the cut, I don't think it will. Might be worth checking with the manufacturer but I now think you would end up needing the check after the sprinkler control valve as Travis had suggested. Apoligies for the distraction