calculating extended coverage and standard spray heads

[skdesigner]

I have been reviewing some drawings and calculations done with sprinkcad and have come across something I have not dealt with before, being an autocad/manual entry hydraulic calc kind of guy. In a parking garage, extended coverage sprinklers have been used in a 16' wide bay, to eliminate one branch line. The next bay is 24', which means two lines of standard spray sprinks. The calc area picks up sprinklers on both the extended coverage line and the standard spray lines. The starting pressure and flow for the extended coverage heads is correct, but the 5.6k standard spray heads have been simultaneously calculated based on providing 0.15 gpm over 130 sq. ft. So, the calc shows 11.2K heads discharging at a minimum of 12.1 psi and 39 gpm. The standard spray heads are discharging at a minimum pressure of 12.2 psi and 19.5 gpm.

NFPA 13-2010 22.4.4.6.1.1 Where sprinklers are required to discharge a specific flow or pressure rather than a density, each sprinkler in the design area shall discharge at a flow or pressure at least equal to the minimum required.

Am I wrong in thinking that the standard spray heads should be shown to discharge at least 12.1 psi at 39 gpm?

Thanks in advance!

 

[SprinklerDesigner2]

With k5.6 sprinklers required to discharge 19.5 gpm @ 12.2 psi while the extended coverage sprinklers are required to discharge a minimum of 39.1 gpm @ 12.1 psi. Sounds correct to me but what one needs to be careful of us the "most remove area" might not be (it actually probably isn't) the most remote area. Like a grid, only shifting by line and not head, the calculated area might include 1 line of 3 heads on the extended coverage heads then 2 lines of 4 heads for the standard head lines. But then how do we know the most remove area (we will correctly call this the hydraulically most demanding area) isn't 3 lines of 4 heads on the extended coverage head lines then 1 line of 4 heads on the standard head lines? Obviously we don't, not until you shift them yourself to check.

 

[skdesigner]

Thank you for the reply SD2. It just looked a little odd to me.