You have asked the following questions: “A local jurisdiction is stating that the system with three loops meets the requirements for a grid system per NFPA 13D. This would require hydraulic calculations per NFPA 13 by 10.4.6. Is it the intent of NFPA 13D to calculate these systems per NFPA 13? Currently, we calculate these systems with a two-head hydraulic calculation per NFPA 13D section 10.2.1. We calculated all points of connection between the loops as indicated with the hydraulic node placement for all lengths, fittings, and pipe sizes throughout the system and through all paths. Would this application require more than a two-head calculation? Also, is the intent of NFPA 13D to change the number of heads that need to be hydraulically calculated …show more content…
This section then provides five different architectural ceiling applications where this criterion applies. The piping configuration to the two sprinklers can be gridded per 10.3.2. The general pipe sizing method of 10.4.4 and the prescriptive pipe sizing method cannot be used since the piping is gridded. As such, the hydraulic calculation procedures in accordance with NFPA 13 shall be used for grid-type systems per 10.4.6 and looped-type systems per 10.4.7. The intent is to hydraulically calculate the gridded system to flow two sprinklers with the highest demand. The calculation procedure in 23.4.4 does say that for all systems the design area shall be the hydraulically most demanding based on the criteria of Chapter 11, Chapter 12, or the special design approaches in accordance with the requirements of Chapter 22. It is not the intent to require the criteria of 11.3.1 for residential sprinklers in NPFA 13 to calculate four adjacent sprinklers that produce the greatest hydraulic demand. Thus, your approach met the intent of the NFPA 13D standard by hydraulically calculating the two most demanding