Attics and 4-12 pitch 3

[AbbyNormal]

Have a wood truss attic over a nursing home, 24" o/c truss spacing

Looking at 15x 8 spacing option with 7 psi minimum pressure available at the head.

2002 13 handbook has an asterix stating the smallest dimension is measure perpendicular to the pitch. So it is somewhat confusing, is this 8 foot up along the pitch or 15 foot up along the pitch.

Second question, can you use a quick response 7/16 head k=4.2 with the 7 psi pressure available, the piping would be a galvanized main with blazemaster branches. A year round cooling environment no freeze concerns so wet system up there.

It would sure cut down the water demand.

Otherwise, why even call it light hazard, call it ordinary II and look for a 0.2 gpm/sq ft density.

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[cdafd]

AbbyNormal

Am I reading this right you are using plastic pipe for the attic system????

If so HOW????

not a designer, or train engineer so do not know if thisc can help you:

http://tyco-fire.com/TD_TFP/TFP/TFP610_12_2007.pdf

 

[mx272]

15' is measured along the slope. Cannot use plastic. With the 4.2K you need to use a stainer device. 5.6K is the sprk to use at 7 psi.

 

[TravisMack]

The 8' dimension is measured perpendicular to your trusses (typically the dimension your branch line runs). The 15' is measured along the slope.

You are not allowed to use Blazemaster piping with exposed standard spray sprinklers as you described. You could use Blazemaster with Tyco Attic Sprinklers if they are applicable for your job. Also, if you are using SSU's to protect the attic space, I don't believe you can use blazemaster to supply the ceiling sprinklers on that level either. You should really check the blazemaster and tyco attic sprinkler data sheets to further clarify this for yourself.

Finally, 4.2k sprinklers are acceptable in attics for wet systems and use the 7 psi sprinkler. Also, you don't need a strainer for a 4.2K sprinkler. You only need a strainer when you have a k-factor less than 2.8. I use K4.2 all the time in wet system attics. You space sprinklers on the slope but calculate on the flat. Therefore, with a 4:12 pitch, you are going to get a max of around 110 sq ft for your area of coverage. With a K5.6, you will be overdischarging each sprinkler as 7psi is 14.82 gpm. With a 4.k sprinkler, 7 psi gets you 11.1 gpm. This is going to save you a lot on system demand.

Also, because of your slope, don't forget the 30% increase in the design area. If you attic is less than 20' tall, you can apply the QR reduction to your design area in addition to the 30% increase for slope.

Good luck!

Travis Mack
MFP Design, LLC

 

[mx272]

Travis
You are correct on the use of 4.8K without a strainer. I should have looked it up in 13. I knew there was a reason for not using the 4.8K's up here in the north. Its because you can only use the 4.8K's on wet systems. Our attic systems are usually dry.

 

[AbbyNormal]

What prohibits blazemaster in an attic?

It is basically CPVC, and that is used for domestic hot water. Is it a temperature and pressure rating issue?



Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[AbbyNormal]

With the 4.2k heads are you forced to go with 20 psi?

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[AbbyNormal]

This attic could also be sealed, temperature would not be much warmer than the conditioned space.

The piping could also be galvanized.

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[AbbyNormal]

The 8' dimension is measured perpendicular to your trusses (typically the dimension your branch line runs). The 15' is measured along the slope.

You are not allowed to use Blazemaster piping with exposed standard spray sprinklers as you described. You could use Blazemaster with Tyco Attic Sprinklers if they are applicable for your job. Also, if you are using SSU's to protect the attic space, I don't believe you can use blazemaster to supply the ceiling sprinklers on that level either. You should really check the blazemaster and tyco attic sprinkler data sheets to further clarify this for yourself.

Finally, 4.2k sprinklers are acceptable in attics for wet systems and use the 7 psi sprinkler. Also, you don't need a strainer for a 4.2K sprinkler. You only need a strainer when you have a k-factor less than 2.8. I use K4.2 all the time in wet system attics. You space sprinklers on the slope but calculate on the flat. Therefore, with a 4:12 pitch, you are going to get a max of around 110 sq ft for your area of coverage. With a K5.6, you will be overdischarging each sprinkler as 7psi is 14.82 gpm. With a 4.k sprinkler, 7 psi gets you 11.1 gpm. This is going to save you a lot on system demand.

Also, because of your slope, don't forget the 30% increase in the design area. If you attic is less than 20' tall, you can apply the QR reduction to your design area in addition to the 30% increase for slope.

Good luck!
Travis Mack
MFP Design, LLC

Thanks Travis

This is a wet system, and a rare one for this location being it is a single story building where you could actually get by on muncipal water pressure rather than do what is typical, and that is a cistern holding the required water volume plus a fire pump. Usually the pumps ended up vertical.

Starting with 7 psi at k=5.6 means a lot of water, where it might as well be called an Ordinary II situation. So it would be 2/3 the water with the smaller heads, then lower with a quick response credit.

Concerning the spacing, I was looking at a 120 sq ft max coverage from Table 8.6.2.2.1(a) of 2002

Reading what they say about blazemaster in the tycho cut sheet that cdafd posted it sounds like a real pain so might as well run galvanized.

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[TravisMack]

Why run galv? You don't have a dry system. Do you normally run galv in wet systems? Out here, it would just be black pipe wet system in the attic.

Travis Mack
MFP Design, LLC

 

[cdafd]

http://www.harvelsprinklerpipe.com/design_installation/pdf/installation-instructions.pdf

if you look at the listing for blazemaster, it will tell when,where and how it can be used.

for attic protection: not allowed

for the protection of the area directly below the attic ceiling, it can be used with stipulations, going back to the listing.

http://www.blazemaster.com/designSpecification/listingsApprovals.asp

CPVC is not approved for use in combustible concealed spaces where sprinklers are required to protect these areas as defined by NFPA 13, unless certain specific application sprinklers are installed per their listing. Refer to Harvel’s current Installation Instructions for additional information.

http://www.harvel.com/tech-specs-fire-sprinkler.asp

 

[AbbyNormal]

I am on an island Travis surrounded by ocean, salt problem. Black iron won't last.

If I sealed the attic slightly conditioned it it would be fine, you could almost call it a concelaed space.

Black iron in a vented attic would not last.

I was just in a hanger at the airport. 10 year old galvanized piping for the foam system is fine.

A black iron main cutting acorss there for sprinklers is 8 years old and ready to blow.



Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[AbbyNormal]

Thanks cdfad.

It looks like they have loopholes still but not worth the hassel for an attic.

I have used it several times on 13R systems running it through attics for the living space below and never had an issue with the blazemaster up there.

Thanks for pointing out the problems with attics.



Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[TravisMack]

Abby:

General rule of thumb is that you can install blazemaster in areas where you don't need sprinklers. The listing has been expanded to some exposed installations in light hazard and concealed combustible spaces when using specially listed sprinklers.

I just tell everyone to go with the basic rule of thumb noted above. We can then get specific on a project if plastic is really desired for various reasons.

Travis Mack
MFP Design, LLC