Dry pendants from attic - zoning issue

[rmae]

Hi,

I'm doing a design for an existing nursing home. Being a full NFPA 13 system the combustible attic space will require sprinkler. The building is existing (only 4 years old) and should have had sprinkler in the beginning but someone missed the requirement and permit was somehow issued and the building built and occupied.

The majority of the construction is vaulted ceilings which would lead to a nasty configuration of exposed piping. My intent, to the liking of the owners, is to utilize dry pendant sprinklers fed from the attic dry system.

My concern is, in Canada the applicable National Building Code of Canada (Code) requires that each sprinkler zone storey annunciate separately per 'storey'. By the Code an attic is not considered a storey however the definition of a storey is:

Storey means that portion of a building that is situated between the top of any floor and the top of the floor next above it, and if there is no floor above it, that portion between the top of such floor and the ceiling above it.

(note that the 'storey' ends at the ceiling, not the roof in the attic)

In your best opinion, do you think that I need to supply the dry pendant sprinklers serving the occupied floor level from a separate dry pipe valve (and hence separate zone) or would you consider the attic and the occupied floor area to be the same storey and hence one zone?

Comments and insight is greatly appreciated....

 

[skdesigner]

Nice to see a fellow canuck here.

In my opinion, "occupied" is the key word. NBC defines "storey" and "attic or roof space" separately.

NBC 2005 3.2.4.15(1) an automatic sprinkler system shall be equipped with waterflow detecting devices ... shall be installed so that each device serves

a) not more than one storey
b) an area on each storey that is not more than the system limits as specified in NFPA 13

NBC does not appear to qualify an attic as a storey.
I would say that, unless it's a real big nursing home (<52000 sq. ft) one zone should suffice.

A quick call to your local AHJ would probably clear it up in a hurry.

 

[rmae]

Thanks skdesigner,

That's my take on this too. I am acting as AJH on this job so want to be as close to 'full code compliance' as possible.

Cheers

 

[byrnesf]

rmae,
Unless I am misunderstanding your terminology for sprinkler heads, why would you use dry pendant sprinkler heads on a dry pipe system?

 

[skdesigner]

byrnesf:

NFPA 13 2010 7.2.2 The following types of sprinklers and arrangements shall be permitted for dry pipe systems:

(1) Upright sprinklers
(2) Listed dry sprinklers
(3) Pendant sprinklers and sidewall sprinklers installed on return bends, where the sprinklers, return bend and branchline piping are in an area maintained at or above 40F(4celsius)


It gets a heck of a lot colder up here in Canada than 40F

 

[rmae]

....listed dry sprinklers=dry pendant sprinklers....

 

[pipesnpumps]

All pendants on dry systems are dry pendants except where heated (and if it is heated why would you need a dry system anyway?).

The only time dry pendants aren't used on dry systems is when a dry system is chosen for the unheated areas, and there a few small heated areas, such that it is not worth installing a separate wet system riser for those areas.

It is not very obvious to a casual designer familiar with wet systems, but think about if the dry valve tripped and filled the system with water. You would have to drain the water out of every head that is installed on a return bend.. Not all would fill up with water but some would. Just depends on the air pressure vs water pressure, and the volume of the branch and drops..

 

[rmae]

byrnest,

We are utilizing 'dry pendant sprinklers' because we want to feed the sprinklers from the attic, cold space, dry piping (due to vaulted ceilings). We use dry pendants so there will be no water in the 'drop' portion of the piping that feeds the sprinkler if the system activates and fills with water.
If you used regular pendants then water would get trapped in the drop and hence could freeze. This job is Saskatchewan where water mains get buried 9 feet below ground because of the cold.
Hope this clarifies.....

 

[skdesigner]

Saskatchewan, you say?

SK in SKdesigner.

hmm, I think I bid the job in question.

Small world, rmae.

 

[rmae]

hmmmm small indeed!

 

[byrnesf]

rmae,
I now understand your reasoning for the use of the dry pendant. I am in Michigan, where dry systems are used also, however none of the systems that I have reviewed or inspected have used dry pendants on dry pipe systems, probably for cost savings reasons. Thanks.

 

[rmae]

I agree byrnest, I had a job a few years back where my client
'definitely' didn't want exposed piping and they went with the dry pendants. I had the contractor price it both ways (wet exposed with pendants/uprights vs. dry pendants fed from attic) and the dry pendant system was nearly triple the cost,
they went with it anyway, go figure. Same case with my present project, they want me to produce two separate tender drawings so the contractors can price it both ways.......

Cheers

R M Arsenalt Engineering Inc.

http://www.rmae.ca

 

[ChrisConley]

Very small world, wouldn't expect to see three people from a small province of a million people on the site... but here we are.

 

[skdesigner]

No kidding. Up here in Saskatoon you can count the number of sprinkler designers on one hand.