Attic System Design 1

[jkampana]

Please see attached PDF for reference. I am having a heck of a time getting this system to work and I have ran out of ideas so I figured I would come here and see if any of you can see an option that I may be missing.

This is an assisted living center with a NFPA 13 system. It is fed from a riser in the South West corner of the building. Dwelling units and common areas are protected by pendents that are fed from CPVC piping tented in the attic. This forces me to use attic sprinklers that are listed for protection of CPVC piping. Attic system is a dry system to add to my frustrations. At this point, in order to satisfy demand I am having to run a 4" main line throughout most of the building with 2" & 1 1/2" branch lines everywhere else. This pushes my system over 1000 gallons which will force me to have a specific water delivery time.

Does anybody have any design suggestions that I may be missing in my layout that may help reduce pipe sizes to get my system volume down?

 

[MatthewJWillis]

Welcome to large attics and the BB sprinklers.

The only things that have worked in the past is adding Exhausters at the end runs. These are expensive.

Optimally, adding system risers to split the volume is best. Though no one wants to run separate underground feeds etc..

Do you have FDT (INSERT TRADEMARK SYMBOL HERE) from TYCO? It always helps to know what the actual is showing now..

Your pipe sizes look good considering what is being delivered..

Good Luck

R/
Matt

 

[chevy4x4trucks]

If there is any opportunity to get your dry valve located more towards the center of the building that would at least help split up your volume and help trap air into one side of the system when the valve trips to give you a more fighting chance of hitting a 60 second delivery time. As it is right now I think you will have a very difficult time getting water delivery in 60 seconds.

A low pressure dry valve would be your best option since your system is pretty much one long line so you want to get as little resistance as possible from air pressure.

But I agree with Matt that you should run this through FDT and see what kind of water delivery time you get with the software. It will take a while to input it since it looks like you are working with HydraCAD, but it would save you a lot of headaches later on when it's time to test.

 

[TravisMack]

A couple things there:

1 - I assume at the hips, you are using Tyco AP sprinklers. They can only protect up to 3000 sq ft, then must be separated from other areas by 15' of BB sprinklers. You may have exceeded that in some areas.

2 - Don't forget you will need to put those BB sprinklers on sprigs where they are directly on the pipe.

3 - You may have to run a wet main under the insulation tent to locate a second dry valve some where in the building to cut your system size.

As Matt stated, that is the problem with big attics and dry systems. You will of course have an accelerator, and these make a big difference in trip times. You can use a low differential dry pipe valve to reduce system air pressure. Being that you have a tree, it will trip faster than a loop will. I have seen tree systems of 1250 gallons trip in <30 seconds with a Tyco QRS accelerator, but it also had about 150 psi sitting under the dry valve due to the fire pump.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[cdafd]

AP heads require 60 second no matter what.

Have seen large systems meet the 60 second with no problem lately, but we have good water, and a quick opening device

 

[jkampana]

Thank you for all of the replies. I had a long talk with the TYCO technical department to make sure I am designing the system within spec and just as Travis stated, I was incorrectly using the AP heads and I had to scrap my design (for the 3rd time.) The good news is that I redesigned the system and it calcs out (with 5 separates remote areas) and I was able to get system volume barely under 750 gal. I still have to meet a 60 sec water delivery time because of the use of AP heads but I am working with TYCO to make sure that will be doable.

Also, I will be putting all the heads on sprigs. I currently do not have sprig tags because I hadn't raised the drawing up to get elevaitions. Thank you all for the ideas. I will keep these in mind next time I run into this issue and cannot remedy it.

 

[MGXFP]

Not to be a buzzkill but it looks like your hip sprinklers are on downward sloping pipe. Will this trap water when you hydro/inspectors test the system? I'd hate for you to have to return for freeze damage down the road. Typically I'll run a dry main somewhere near the eave and rise up using swing joints with hip sprinklers on the top of the line so everything drains.

Recently we installed a large ~750 gallon dry system with about 65 psi static water and met the 60 second test time. We used a victaulic NXT with 13 psi air pressure and QOD IIRC.

 

[jkampana]

NewtonFP, I changed my design completely and now have no HIP sprinklers at all in this project. I also have made sure that everything slopes back to the riser on one end and 2 drum drip drains located in the center and remote wing of the building. I typically like to get my calculations and sizing figured out then I design the slope in my pipe. So I hadn't even got to that portion of design yet.

My system volume is now down to about 680 gallons. We have 88 psi residual. So hopefully the 60 sec delivery time isn't an issue.

 

[cdafd]

JK

Are you just using standard heads?

No tyco attic heads at all?

 

[jkampana]

No, I am still using Attic heads. I have BB heads at the peaks, SD heads at the outside HIPs and AP head covering the interior of the hips. Each area oh AP heads is less than 3000 sf and separated from another area of AP heads by at least 15 feet. I also have AP heads in the dormers as well.

 

[SprinklerDesigner2]

I think I have shared this with the forum before but in case someone missed it.

A Technical Analysis: Variables That Affect The Performance Of Dry Pipe Systems
James Golinveaux, Sr. Vice President,
Research & Development
Tyco Fire & Building Products

If you don't have this you will want to grab it.

About two years ago I had a large dry pipe system, I forget the exact size but I think it was approaching 1,400 gallons, and needless to say I was very concerned with trip times seeing as how all we had was 65 psi static from the city but going for us it was a very flat curve.

After reading the paper I figured I would try some experimenting and setting up the system I made it so I could add an additional dry pipe valve if needed and as I already had it figured in my price no great harm would be done. It was a gamble, worth risking $1,000 in labor and re-submittal of plans to save $4,000? I thought it was.

So I ended up fighting the dry valve and I won!

What I had was two large tree systems and what I did on the last line was simply tie the two end branch lines together with 1" pipe making the system a "loop" if you will.

I was taught "loops are bad because you got to fill up all the pipe before water gets to the inspectors test" and did I ever prove myself wrong on that.

I tried it both ways, fitters wanted to drink beer but I wanted to see for myself, to discover ten feet of 1" pipe with a union cut 15 seconds off the time water to the inspectors test connection.

This might be old hat to some of you but I was completely floored because it went against everything I've been taught for 40 years.

But when you think about it, analyze a bit, it makes sense that it would cut the time because it gives the air someplace else to go other than through a small orifice and globe valve.

I learn something new every day.