I have a 12 story building with the following fire system characteristics:
- wet-pipe combination standpipe system
- 2 standpipe risers with 2-1/2" PRV hose valves and standard valve caps
- 500 gpm fire pump (117 psi @ churn, 82 psi @ 150%) supplied from city water with 45 psi at pump inlet
Since the hose valves are 2-1/2" (NFPA 14 3.3.22.1) and not equipped with a 2-1∕2 in. × 1-1∕2 in. reducers (NFPA 14 5.3.3.2) then it would be safe to assume that this is a Class I standpipe system, right?
Since the building is 12 stories tall it would classified as a high-rise building (NFPA 14 3.3.9), which would mean the standpipe system must be of the automatic type (NFPA 14 5.4.1.2), right?
And an Automatic Class I standpipe system would be required to provide residual pressure of 100 psi at the most remote hose connection (NFPA 14 7.8.1), while simultaneously flowing 500 gpm from the most remote hose valve (NFPA 14 7.10.1.1.1) and 250 gpm from the second standpipe riser (NFPA 14 7.10.1.1.3), for a total of 750 gpm, right?
And if I assume that the building is 120 ft. high (12 stories * 10 ft. = 120 ft.) that's a head loss of 52 psi, right?
And if the fire pump produces 82 psi @ 150% (750 gpm), and has an inlet pressure of 45 psi, that's a discharge pressure of 127 psi @ 750 gpm at the 1st floor, and 75 psi at the 12th floor, right?
So how is this supposed to be an automatic standpipe system if the pump can't provide a residual pressure of 100 psi at the most remote hose connection while flowing a total of 750 gpm? Which one of these things did I get wrong here?
- wet-pipe combination standpipe system
- 2 standpipe risers with 2-1/2" PRV hose valves and standard valve caps
- 500 gpm fire pump (117 psi @ churn, 82 psi @ 150%) supplied from city water with 45 psi at pump inlet
Since the hose valves are 2-1/2" (NFPA 14 3.3.22.1) and not equipped with a 2-1∕2 in. × 1-1∕2 in. reducers (NFPA 14 5.3.3.2) then it would be safe to assume that this is a Class I standpipe system, right?
Since the building is 12 stories tall it would classified as a high-rise building (NFPA 14 3.3.9), which would mean the standpipe system must be of the automatic type (NFPA 14 5.4.1.2), right?
And an Automatic Class I standpipe system would be required to provide residual pressure of 100 psi at the most remote hose connection (NFPA 14 7.8.1), while simultaneously flowing 500 gpm from the most remote hose valve (NFPA 14 7.10.1.1.1) and 250 gpm from the second standpipe riser (NFPA 14 7.10.1.1.3), for a total of 750 gpm, right?
And if I assume that the building is 120 ft. high (12 stories * 10 ft. = 120 ft.) that's a head loss of 52 psi, right?
And if the fire pump produces 82 psi @ 150% (750 gpm), and has an inlet pressure of 45 psi, that's a discharge pressure of 127 psi @ 750 gpm at the 1st floor, and 75 psi at the 12th floor, right?
So how is this supposed to be an automatic standpipe system if the pump can't provide a residual pressure of 100 psi at the most remote hose connection while flowing a total of 750 gpm? Which one of these things did I get wrong here?