8.7.4.1.2 Walls.
8.7.4.1.2.1* Vertical sidewall sprinkler deflectors shall be lo- cated not more than 6 in. (152 mm) or less than 4 in. (102 mm) from the wall from which they are projecting.
8.7.4.1.2.2 Horizontal sidewall sprinkler deflectors shall be located no more than 6 in. (152 mm), and shall be permitted to be located with their deflectors less than 4 in. (102 mm), from the wall on which they are mounted.
""""Do HSW sprinklers require a wall behind them? It would seem strange to me that would be a requirement but the local AHJ believes it is.""""
Is this a general question or do you have a specific application ???
How about under overhead doors??? Does 8.7.4.1.2.1* Vertical sidewall sprinkler deflectors shall be lo- cated not more than 6 in. (152 mm) or less than 4 in. (102 mm) from the wall from which they are projecting.
So when the overhead door is closed it is not an obstruction. But if the door is open it does present an obstruction and the door acts as the heat collector for the sprinkler. You can not have a sprinkler just sticking out in mid air and hope it will activate, they need heat a lot of it for a period of time to work.
""""""""So when the overhead door is closed it is not an obstruction. But if the door is open it does present an obstruction and the door acts as the heat collector for the sprinkler. You can not have a sprinkler just sticking out in mid air and hope it will activate, they need heat a lot of it for a period of time to work.
Not sure if that helps. """"""""""
agree, but there is no "Wall" behind it like it sounds the OP is saying the ahj requires.
I think the section you quoted is the criteria for "placement"
And not sure if the OP is asking a general question or has a specfic problem????
How does a wall help activation? For example imagine an infinitely large ceiling with no walls. For activation purposes, whats the difference between having a pendent sprinkler 6" below the ceiling as opposed to a HSW? The only difference between the two sprinkler types is the deflector, which does not impact activation.
For example, I don't see why in my example of a room with no walls you can't replace the pendent with back-to-back HSW's that are within 8" of each other and comply with equal or better coverage compliance.
You can, just need a soffit between them. NFPA 13-2010 8.7.3.1.4 Sidewall sprinklers shall not be installed back to back without being separated by a continuous lintel or soffit.
The 13 handbook provides this explanation: "The use of a lintel or soffit is necessary to ensure that the sprinkler closest to the fire operates and to minimize the possibility of sprinklers on both sides of the lintel operating unnecessarily. The baffle also serves to prevent the discharge pattern of the operating sprinkler from impinging on the operating element of an adjacent sprinkler. The baffle is an important feature, because sidewall sprinklers are actually designed to discharge a portion of their spray pattern behind the sprinkler."
The sidewall doesn't need the back wall to help with activation, it needs the back wall to end the room because a sidewall only sprays one direction effectively.
Interesting, we have a situation where we have a HSW installed 4" below the ceiling with no wall in the area. However, 6' behind the HSW we have a standard spray pendent. All floor area is protected. It seems to me in this situation there are no issues with cold soldering or incorrect sprinkler activation.
It is not practical to install a pendent in the area protected by the HSW.
I have seen contractors that use two side wall in the same pipe facing away fron each other to cover under garage door. Kind like this -I- is that correct?
