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bobinillinois (Mechanical) (OP)
22 Feb 11 17:38
The 2007 NFPA 13.8.6.3.3 says that sprinklers shall be located a minimum  of 4" (102mm) from a wall.

My state's architect responsible for Life Safety has said that his interpretation of this is that the deflector must be at least 4" from the wall.  Based upon the width of different sprinkler deflectors that can move the center point of your sprinklers some distance one way or the other.  

I've discussed the same issue with one of the "ask the expert" folks who disagrees with this interpretation.  His take on it was that based upon figure 8.6.4.1.1.3 the distance is to be measured from the wall to the center of the sprinkler.

I tend to agree with the architect's interpretation as the code says "sprinklers" must be a minimum of 4" from a wall, not the "center of a sprinkler" or "a sprinkler's element."

What say you?

 
stookeyfpe (Specifier/Regulator)
22 Feb 11 17:48
The purpose of the requirement is to ensure the sprinkler is located so that it can respond to fire gases captured at the ceiling. Given the fusible element in an upright or pendant sprinkler is in the center of the device, I've always measured to the center.

However, I've never really questioned as to how the dimension is measured so I look forward to other opinions.
cdafd (Specifier/Regulator)
22 Feb 11 17:55
agree you want the fusiable element four inches out, so middle of the deflector
NJ1 (Mechanical)
22 Feb 11 21:30
I totally disagree with stookeyfpe.
The purpose of this requirement is to allow for a proper development of a spray pattern and not so that it can respond to fire gases captured at the ceiling.

NFPA 13 indicates that the distance from the wall to the sprinkler shall be measured perpendicular to the wall.
It does not says anything about being measure from the side, front, top, etc of the sprinklers.
However it only makes sense to measure from the center to avoid writing multiple codes based on the many different sizes of deflectors in the industry.

Also, if the distance between sprinklers shall be based on the centerline between sprinklers then it also makes sense to apply same rule to distance from walls.  
chevy4x4trucks (Mechanical)
22 Feb 11 21:53
I concur with Stooeyfpe based on some classes/training with NFSA. This rule is because the heat and gasses don't make a hard 90 degree turn at the ceiling, they do more of an arc.  This is the same reason sidewalls need to be down a minimum of 4" as well.


I would say the 4" is to the center of the head.  Even with an extended coverage head the deflector isn't going to be more than 2".  If you are designing / installing them with that tight of a tolerance to a wall you are just asking for trouble.
NJ1 (Mechanical)
22 Feb 11 22:04
Well i just go with what it says on NFPA 13. This issue is adressed on the chapter of positioning of sprinklers and obstruction to spray patterns.  
pipesnpumps (Mechanical)
22 Feb 11 22:09

Huh.. I also thought the minimum 4" was there so that it wouldn't affect the spray, due to 'backsplash effect' (for lack of a better term) screwing up that heads spray pattern and throw distance in the direction away from the wall.

I thought Ron Cote's advisory notes in the 13 handbook stated as such, but it also makes absolute perfect sense about the heat plume..  

That is very analogous to the passages from NFPA 72 that prohibit heat detectors from being located in the same "corner" of thermal dead space.


 
FFP1 (Mechanical)
22 Feb 11 23:16
Heat generation creates an upward draft (hot air rises).......air flows upward along the interior surface of the wall. As the air flow approaches the ceiling, the hot air curves due to the presence of the ceiling. This phenomenon results in little or no air flow in the corner area created by the wall and the ceiling. The limited air flow essentially holds a pocket of air in the corner.......any fusible elements (i.e. sprinklers) in this area typically take longer to activate during a fire incident. I vaugely remember reading about temperature sensors strategically located along the ceiling and walls during fire testing to verify this fact.

Think about dust, hair-balls and even spider webs......these accumulations are commonly found in the corners at the ceiling level and on floors due to limited air flow in the transition between a vertical wall and a horizontal ceiling. There is some law or effect named after the man who identified and documented this phenomenon; however, I do not remember hs name (Darcy maybe??).

Stookey is correct (based on my opinion and limited knowledge in this matter).......the primmary reason behind the 4 in. requirement is to prevent delayed aprinkler activation.

After the sprinkler operates, why would it matter if the water hits a vertical wall just 1-2 in. away from the sprinkler?? Everything within the protected circle or sprinkler umbrella pattern will still get wet (as long as there are no other obstruction issues of course!).

Most sidewall sprinklers also must be installed between 4-6 in. below the ceiling due to this corner issue (this requirement also allows the spray pattern of the sidewall sprinkler to develop properly; water throws slightly upward prior to the effects of gravity causing the downward fall).

Now back to the original question.......install all sprinkler deflectors >4in. from the wall and/or measure from the deflector to the wall and the point is mute. The more conservative approach is usually better when dealing with NFPA requirements; this way individual opinions (i.e. lawyers or professional witnesses in court) do not matter.
 
NJ1 (Mechanical)
23 Feb 11 18:58
You know what Stookey could be right however I am going to type NFPA says:

NFPA 13-2002
Chapter 8-Installations Requirements
Section 8.5-Position, Location, Spacing and use of Sprinklers

8.5.1.2
Sprinklers shall be positioned to provide protection of the area consistent with the overall objectives of this standard by controlling the position and allowable area of coverage for each sprinklers.(it only speaks about the proper coverage)
             
8.6.3.2.2
The distance from the wall to the sprinkler shall be measure perpendicular to the wall.
8.6.3.3
Sprinklers shall be located a minimum of 4" from a wall

I believe stookey's comment could refer to sprinklers located too close to ceilings rather than walls.



              
b1ueshift (Mechanical)
24 Feb 11 3:34
Does this come up a lot?

I don't think I've ever seen a sprinkler that close to a wall.  I think it would only happen if someone were to build a wall next to an existing sprinkler.   
cdafd (Specifier/Regulator)
24 Feb 11 10:43
yes it does come up for various reasons
Helpful Member!  ChrisConley (Mechanical)
24 Feb 11 10:52

Quote:

You know what Stookey could be right

This made me laugh out loud. If stookey posted that NFPA called for sprinklers to be installed in cars I'd be designing car sprinkler systems later that day.
Helpful Member!  skdesigner (Mechanical)
24 Feb 11 13:26
In response to the OP's question (the 4" dead space comment hits the nail on the head, see the 13 handbook explanation for 8.6.3.3), because 13 doesn't seem to address this, I'm going to agree with pipesnpumps' reference to 72.  NFPA 72 Figure A17.6.3.1.3.1 illustrates what 13 is saying in 8.6.3.3, and contains a note stating: measurements shown are to the closest edge of the detector.

I would consider the bulb/link to be the detector, and not the frame of the sprinkler.

 
AZsprink (Mechanical)
25 Feb 11 1:51
We install concealed sprinklers 4" min. from the edge of the coverplate to the wall, as the solder for the coverplate is at the edge of the cover, not the center of head. I don't know if this is code, but I think it should be.  
fireguy519345 (Structural)
26 Feb 11 14:34
If the pipe is exposed, can you install the deflector or the link/bulb within 4 inches of the wall.  I am in the office, and do not have a sidewall and tee handy.   

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