TYCO BB is not a standard spray sprinkler so 8.6.5.2.1.3 is not applicable.
The specific application requirements from the listing and manufacturer’s instructions are in order. J. Scott Mitchell, PE Senior Fire Protection Engineer Mission Engineering CNS PTX / Y-12 | 865-576-5258 From: Sprinklerforum [mailto:sprinklerforum-boun...@lists.firesprinkler.org] On Behalf Of Richard Mote Sent: Thursday, October 25, 2018 11:33 AM To: sprinklerforum@lists.firesprinkler.org Subject: Obstructions in Light Hazard Attic We have an attic where the designer placed TYCO BB head directly on a 4" line running at the peak. They should have been on sprigs but it wasn't caught in the design stage. NFPA 13, 2007 in section 8.6.5.2.1.4 States that for light and ordinary hazard occupancies structural members only shall be considered when applying the requirements of 8.6.5.2.1.3. 8.6.5.2.1.8 States The requirement of 8.6.5.2.1.3 shall not apply to sprinkler pipe less than 3 in. (80 mm) in diameter. So which is it? In light and ordinary hazard can you ignore the non structural obstructions and only apply them in extra hazard occupancies? This seems like a circular argument. Excerpt from NFPA 13 below to save looking it up. 8.6.5.2.1.3* Minimum Distance from Obstructions. (A) Unless the requirements of 8.6.5.2.1.4 through 8.6.5.2.1.9 are met, sprinklers shall be positioned away from obstructions a minimum distance of three times the maximum dimension of the obstruction (e.g., structural members, pipe, columns, and fixtures). (B) The maximum clear distance required shall be 24 in. (609 mm) in accordance with Figure 8.6.5.2.1.3(B). 8.6.5.2.1.4* For light and ordinary hazard occupancies, structural members only shall be considered when applying the requirements of 8.6.5.2.1.3. 8.6.5.2.1.5 Sprinklers shall be permitted to be spaced on opposite sides of the obstruction where the distance from the centerline of the obstruction to the sprinklers does not exceed one-half the allowable distance between sprinklers. 8.6.5.2.1.6 Sprinklers shall be permitted to be located one half the distance between the obstructions where the obstruction consists of open trusses 20 in. (0.51 m) or greater a part [24 in. (0.61 m) on center], provided that all truss members are not greater than 4 in. (102 mm) (nominal) in width. 8.6.5.2.1.7 Sprinklers shall be permitted to be installed on the centerline of a truss or bar joist or directly above a beam, provided that the truss chord or beam dimension is not more than 8 in. (203 mm) and the sprinkler deflector is located at least 6 in. (152 mm) above the structural member and where the sprinkler is positioned at a distance three times greater than the maximum dimension of the web members away from the web members. 8.6.5.2.1.8 The requirements of 8.6.5.2.1.3 shall not apply to sprinkler system piping less than 3 in. (80 mm) in diameter A.8.6.5.2.1.4 It is the intent of this section to exempt nonstructural elements in light and ordinary hazard occupancies from the obstruction criteria commonly called the “Three Times Rule.” However, the other obstruction rules, including the “Beam Rule” (see 8.6.5.1.2) and the “Wide Obstruction Rule” (see 8.6.5.3.3), still apply. If an obstruction is so close to a sprinkler that water cannot spray on both sides, it is effectively a continuous obstruction as far as the sprinkler is concerned and the Beam Rule should be applied. It is not the intent of this section to permit the use of fixtures and architectural features or treatments to conceal, obscure, or otherwise obstruct sprinkler discharge. The requirement should be applied in accordance with the performance objectives in 8.6.5.1. Richard L. Mote On Behalf of Rowe Sprinkler Systems
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