Space on opposite sides not to exceed 1/2 the distance and sleep well. 
You wouldn't think twice if this was inside a building 20' off the floor 
would you?

IMHO

Greg McGahan

On 5/27/2010 2:02 PM, Chris Cahill wrote:
> One use of the table is if I can comply with it the next sprinkler can be
> the maximum distance from the first that is taking care of the underneath.
>
> So in a 1' deep 'beam' 1st sprinkler is 3' off the side (assuming a 2.5"
> deflector).  The sprinkler on the other side is up to 15' from the first
> sprinkler.  Doesn't matter where the beam is related to on the second
> sprinkler 'cuz the first will spray under.  And in the 2' wide beam could be
> 10' off the side of the beam with the second head.
>
> But if I'm 2'11" off the side (same deflector of 2.5" down) with the first
> head, then the next head must be at MOST 7.5' from the center of the 'beam'.
> If we have a 2' wide 'beam' the head spacing is only 7.5' plus 1' plus 2'11"
> for 11'4" between the heads.
>
> At times this 3'8" spacing difference might make a difference in what is on
> the other side of the second head.  If it's a wall say 9'6" away from the
> second head you just put in a third head.   But in the first example a third
> head would not be necessary.
>
> In my 5' deep beam problem the chart doesn't go that far so I have no choice
> but to space both sides to the center line of the beam. Really it's become
> an infinitely thin wall on the centerline of the beam for practical
> purposes.  If I don't have something in the way the heads might be 15' apart
> but that's coincidence.  If something is in the way the heads could be as
> close as 2'8".
>
> Chris Cahill, P.E.
> Fire Protection Engineer
> Sentry Fire Protection, Inc.
>
> 763-658-4483
> 763-658-4921 fax
>
> Email: [email protected]
>
> Mail: P.O. Box 69
>          Waverly, MN 55390
>
> Location: 4439 Hwy 12 SW
>                Waverly, MN 55390
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Richard Carr
> Sent: Thursday, May 27, 2010 3:21 PM
> To: [email protected]
> Subject: RE: Beam obstructions
>
>   No, I am not picking any fights either, my option is that table
> 8.6.5.1.2 and figure 8.6.5.1.2(a) 2007, give me a distance I need to
> stay away from an obstruction, if not to throw under that why does the
> distance increase the higher above the bottom you go? Why not just put
> the heads right up against it?
>
>
> Richard Carr, SET
> Design Manager
> Associated Sprinkler Co., LLC
> 336.373.3901 ext 217
> [email protected]
>
>
>
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Chris
> Cahill
> Sent: Thursday, May 27, 2010 4:12 PM
> To: [email protected]
> Subject: RE: Beam obstructions
>
> I don't want to be argumentative but where does it say I have to throw
> under
> it.  The charging section NFPA 13 (2002) 8.6.5.1.2 says comply with ONE
> of
> the following.  Throwing under is an option in (1).  I and Tony choose
> (2)
> which is our prerogative. Its not a comply with ALL section.
>
> We can be 4" off both sides and be compliant.  We can also be 7.5' from
> the
> centerline or anything in between.  It's really no different than a 47"
> duct
> 19" below the deflectors.  And there the distance to the center line is
> irrelevant.  Head can be right on top of the centerline.
>
> Again what if your beam is I described 5' deep which is not uncommon in
> double tee construction.
>
> Chris Cahill, P.E.
> Fire Protection Engineer
> Sentry Fire Protection, Inc.
>
> 763-658-4483
> 763-658-4921 fax
>
> Email: [email protected]
>
> Mail: P.O. Box 69
>          Waverly, MN 55390
>
> Location: 4439 Hwy 12 SW
>                Waverly, MN 55390
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Richard
> Carr
> Sent: Thursday, May 27, 2010 2:55 PM
> To: [email protected]
> Subject: RE: Beam obstructions
>
> You will still need to throw water under it and at 36" deep you will
> have to max out your spacing, hope you have good water supply.
>
> Richard Carr, SET
> Design Manager
> Associated Sprinkler Co., LLC
> 336.373.3901 ext 217
> [email protected]
>
>
>
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Chris
> Cahill
> Sent: Thursday, May 27, 2010 3:51 PM
> To: [email protected]
> Subject: RE: Beam obstructions
>
> Looks like this NFPA 13 (2002) 8.6.5.1.2(2) applies perfectly.  No
> mention
> of construction type or depth as a limit.  8.6.5.2.1.2 specifically
> sends
> you there for continuous obstructions. We call NFPA 13 (2002)
> 8.6.5.1.2(2)
> the 'beam rule' but you'll note never is 'beam' used. It can be used for
> many things that are similar to a beam.
>
> If this doesn't work then I might have a problem with a 2' wide beam 5'
> deep
> holding up double tees.
>
> Chris Cahill, P.E.
> Fire Protection Engineer
> Sentry Fire Protection, Inc.
>
> 763-658-4483
> 763-658-4921 fax
>
> Email: [email protected]
>
> Mail: P.O. Box 69
>          Waverly, MN 55390
>
> Location: 4439 Hwy 12 SW
>                Waverly, MN 55390
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Richard
> Carr
> Sent: Thursday, May 27, 2010 2:39 PM
> To: [email protected]
> Subject: RE: Beam obstructions
>
> With the 3' depth it makes it challenging, can you use extended coverage
> heads?
>
> Richard Carr, SET
> Design Manager
> Associated Sprinkler Co., LLC
> 336.373.3901 ext 217
> [email protected]
>
>
>
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of A.P.Silva
> Sent: Thursday, May 27, 2010 3:35 PM
> To: [email protected]
> Subject: RE: Beam obstructions
>
> NFPA 13 (2002) 8.6.5.1.2(2), for obstructions not exceeding 4 feet
> width.
>
> You don't think that will apply?
>
> Tony
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Richard
> Carr
> Sent: May 27, 2010 1:25 PM
> To: [email protected]
> Subject: RE: Beam obstructions
>
> I would be concerned with NOT protecting the area under the 2' wide
> plywood
> , can't think of any exception that would allow you to not have
> protection ,
> and because of the 3' depth you will have to have heads under the
> enclose.
> My 2 cents worth.
>
> Richard Carr, SET
> Design Manager
> Associated Sprinkler Co., LLC
> 336.373.3901 ext 217
> [email protected]
>
>
>
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of A.P.Silva
> Sent: Thursday, May 27, 2010 2:47 PM
> To: [email protected]
> Subject: Beam obstructions
>
> I have a crawlspace that has to be sprinklered. I need to get exact
> measurements, but for now I'm guessing it is about 4 feet high. The
> plywood
> ceiling of the crawlspace tight to the bottom of main floor joists is
> smooth
> &  flat. The problem is the crawlspace has "utilidors", enclosed heated
> spaces for running ducts, piping etc. Generally, these utilidors,
> encased
> with plywood, are 2 feet wide (horizontal) and about 3 feet high
> (vertical)and run everywhere in the crawlspace, with no set pattern.
> Think
> of the utilidors as wood beams coming down from the ceiling. I will have
> sprinklers inside the udilidors if they are not filled up with ducts or
> piping. My question is there is about a foot of space below the
> utilidors.
> My opinion is it should be okay if I space the heads on both sides of
> the
> obstruction complying with 13(2007) section 8.6.5.1.2 (2) and not
> provide
> additional heads below the obstruction. Any dissenting thoughts?
>
> Tony
>
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