Dry sprinkler heads in Wet-Pipe sprinkler system 2

[madvb]

In areas that don't really freeze (2-3 days out of the year where temperature might drop to 25 deg F), is it possible to use some dry sprinkler heads in a wet-pipe sprinkler system, such as in attic (insulation at ceiling) or under overhangs?

Thanks.

 

[skdesigner]

NFPA 13 2010 A.8.15.7 shows a detail for protecting covered platforms, similar to an eave.

As for attics, it depends how high the dry barrel has to extend to put the sprinkler deflector within the appropriate distance from the roof deck. 8.4.9.1 states that the minimum length of the sprinkler barrel shall be in accordance with the manufacturers listing, to avoid freezing by conduction.

Depending on the length, you're probably looking at a made-to-order sprinkler. At $100++ per head, it better be a small attic to be profitable in any way. Also, if you're sprinkling the attic, I assume it's a full 13 building? Double check with the AHJ to make sure the attic doesn't require a separate zone.

To answer your question, it MIGHT be possible.

 

[madvb]

Thanks skdesigner. I don't have 2010 NFPA yet. It looks like you are referring to Figure A.8.14.7 in NFPA 13-2002, which is what I'm using for this project.

For the attics, It looks like the dry barrel will have extend 5-6 feet above ceiling insulation. Do you have the title of that section 8.4.9.1? I'm not finding anything similar under 2002 edition.

How are these dry sprinkler heads installed in a wet-pipe system? Do they still need an air compressor to pressurized the barrels?

 

[skdesigner]

Don't have 2002 handy, but I'm sure you have the idea for the overhangs.

A 6' dry sprinkler would not be my cup of tea. Like a vertical sprig, you'll have to restrain the barrel. Call some wholesalers for pricing...try not to fall out of your chair when you get the quote.

A dry sprinkler is essentially a pipe nipple with a sprinkler at the end. At the end opposite the sprinkler, there is a plug sealing the barrel, connected thru to the heat sensitive element of the sprinkler. When the sprinkler pops, plug drops and water flows...hence "dry sprinkler".

By virtue of this, the barrel has to extend from the sprinkler down into the warm area a sufficient length (victaulic has some nice literature on sprinkler barrel length). The fitter has to either have his branch line hung, or be pretty damn sure of his elevation before you order up the sprinks.

In your attic situation, your branchline would run in the warm space, with a pipe nipple made into the o'let, 1" tee made on to the nipple, with your dry sprinkler made into the opposite leg of the tee. A 1" plug is made into the tee's outlet. Sounds a bit strange, but if you look at the thread of a dry sprinkler, it's long enough that when fully made into the o'let, it will extend down into the water stream.

No air compressor, dry sprinkler is a sealed unit. Hope I was clear enough. 8.4.9.1 is new for 2010. States " Where dry sprinklers are connected to wet pipe sprinkler systems protecting areas subject to freezing temperatures, the minimum length between the sprinkler and the fitting shall be in accordance with the manufacturers instructions."

 

[MGXFP]

From what you've posted it would seem an anti-freeze loop in the attic would be the best solution. Long dry uprights are terribly expensive and poking that many holes for the uprights to extend up would probably be problematic; especially if the roof is steeply sloped.

 

[cdafd]

heater???

is this just a general question or for a specific building??

 

[NJ1]

I thought that the longest listed dry head is 48" which equals 4 Feet. This attic better be of low ceilings if not dry heads will not work.

 

[cdafd]

8.4.9.1 looks like it is not in the 2002
it is under specail which was 8.4.9 in the 2002


8.4.9 Dry Sprinklers.

8.4.9.1* Where dry sprinklers are connected to wet pipe sprinkler systems protecting areas subject to freezing temperatures, the minimum length between the sprinkler and fitting shall be in accordance with the manufacturers' instructions.

8.4.9.2* Where dry sprinklers are connected to wet pipe sprinkler systems protecting insulated freezer structures, the clearance space around the sprinkler barrel shall be sealed.

 

[madvb]

Thanks skdesigner for the helpful description: A dry sprinkler is a sealed unit. So if that unit pops, you just have to replace the heating element or replace the whole unit? I have to google to see if I can find a picture of that tee you mentioned. Sounds like the tee is to drain any water in the dry barrel once it pops?

NewtonFP: I'll look at the anti-freeze option as well. Going to get a quote from the contractor.

cdafd: I have 3 single story buildings (2 wood framed buildings with 2,000 sf and 3,000 sf, 1 metal framed building of about 2,000 sf). All have 5:12 roof slope with insulation at the ceiling. All buildings fall under NFPA 13 (2002 edition). I think it's around 100 heads in the attic spaces and overhangs for all 3 buildings.

 

[skdesigner]

http://www.tyco-fire.com/TD_TFP/TFP/TFP500_01_2008.pdf

Check out figure 1 on page 2.

Once it goes...it's garbage. The tee is there to maintain clearance for the longer thread on the sprinkler. It isn't necessary for most o'lets, as they are deep enough that the sprinkler can be properly made in and not obstruct the waterway, but it's always good to check.

 

[cdafd]

I think you will find a heater or two will be cheaper and easier

 

[madvb]

cdafd: heater in the attic space where people don't normally go up there? These are small buildings, and they are treated almost like a residential. With the ventilation in the attic, the heater might run all winter.