What a great discussion this has been! I see it as my job to present a design to my customer, the AHJ, and the specifying engineer (and potentially other stakeholders) a design that attempts to address their respective concerns as we attempt to work together to provide a system that offers a reasonable degree of life safety to the occupants. This discussion emphasizes the fact that there is often more than one way to skin the cat, so to speak. This group of EXTREMELY INTELLIGENT individuals have provided great options I can present to the team of stakeholders for this project. In the end, the only way for this to be a successful project is for us to find a solution everyone can be satisfied with.
Thank you all!! PS – not trying to shut down the discussion. Just wanting to acknowledge how much I appreciate all of the input!! Micah Davis Ferguson Fire Design [email protected] On Mon, Sep 25, 2023 at 12:57 PM Eric Rieve <[email protected]> wrote: > Micah, > > > > To add to what Anthony just posted, I think the key point that may have > been missed in your initial question is that the secondary water supply > needs to be “automatic” all on its own. This means that is needs to be > equivalent to the city water supply in available gpm and pressure before it > reaches your primary fire pump. 403.3.3 comments that a secondary fire pump > (as in Anthony’s description) isn’t necessarily required, but I’m assuming > that would be based on the idea that the secondary water supply is gravity > fed from a tank stored higher than the primary fire pump. > > > > So, since it looks like you sized your initial fire pump on the tank water > supply, so you should be able to drop its performance down to the amount > needed to boost the city supply to the 305psi. Your secondary fire pump > would then need to be sized to provide the same 1000gpm at whatever psi you > have from your city connection. > > > > Caveat: The above is just based on a quick read of the question and > relevant code sections, and not based on past personal experience. > > > > Hope this helps! > > Eric Rieve, SET > > Rieve Fire Protection > > > > *From:* Anthony Carrizosa <[email protected]> > *Sent:* Monday, September 25, 2023 12:45 PM > *To:* Discussion list on issues relating to automatic fire sprinklers < > [email protected]> > *Subject:* [Sprinklerforum] Re: Standpipe PRV Question > > > > Micah, > > We typically design ours with a primary pump taking suction from the city > main and a secondary pump taking suction from the tank. > > The primary is of course designed to provide the required pressure to meet > the standpipe design. The secondary pump is sized to provide an equivalent > pressure of the city supply and is tied into the supply to the primary > pump. Thus with either the city supply or the secondary supply the primary > pump output is the same. > > All settings to the controllers come after the primary pump so as it > continues to boost the incoming city supply to the required design > pressures if the city supply where to drop for any reason then the > secondary pump comes on and supplies the needed incoming pressure to this > primary pump. > > > > > > *Anthony Carrizosa * > > Project Manager *| *Fire Protection > > 7855 S 206th St Kent, WA 98032 > > Cell: *206-679-5283* | Office Dir: *253-341-4593* > > https://archerconstruction.com > <https://linkprotect.cudasvc.com/url?a=https%3a%2f%2farcherconstruction.com%2f&c=E,1,Wdb65AWzMgSBzW3HDw91SfcRQCtxDUQKoJf-UowQ-WnB_WMosgG-8W7eLePJ42PwWQvLiQx16Pls052VqwHO7tKm-_u5AnWly0ewkNiMkxn-AjQb1JI,&typo=1> > > > > > > > > *From:* Micah Davis <[email protected]> > *Sent:* Monday, September 25, 2023 9:18 AM > *To:* Discussion list on issues relating to automatic fire sprinklers < > [email protected]> > *Subject:* [Sprinklerforum] Re: Standpipe PRV Question > > > > Thank you for the response, Steve! Does the redundant fill valves for the > tank satisfy the secondary supply requirement of the IBC without an > additional tank? I was interpreting the city main connected to the pump as > the primary supply and the tank as the secondary supply (or vice versa). > If my interpretation is wrong and the tank with redundant fill valves meets > BOTH the primary and secondary water supply requirements, I can NOT connect > the city water main to the fire pump, and the problem is solved using your > method above. > > > > Am I tracking correctly? > > > > My thought is that if the city main stays connected to the pump and my > demand calcs and PRV settings are based on the supply from the tank (which > I think is correct), how do we avoid overpressurization with the added > pressure from the city? I'm probably overthinking this somewhere! That > tends to be my M.O.! > > > > Micah Davis > > Ferguson Fire Design > > [email protected] > > > > > > On Mon, Sep 25, 2023 at 12:02 PM Steve Leyton <[email protected]> > wrote: > > Micah: > > The best way to stabilize the pump discharge pressure and give yourself a > (nearly) straight line suction pressure curve is to arrange the required > secondary water supply as a break tank. Fill the tank with city water > (recommend to manifold at least one automatic plus one manual fill; in my > neck of the woods we use two automatic and one manual) and base your > calculations on the lowest potential water level in the tank. We simply > use the pump’s performance curve as a water supply assuming 0 psi suction > head. Depending on water column height, your actual discharge pressure > variation will be ≤ 5 psi, unless the tank is uniquely configured and > multi-story. > > > > > > The foregoing is my opinion only and does not represent NFPA or the NFPA > 14 Technical Committee, nor intended to serve as an interpretation of the > standard. > > > > *Protection Design and Consulting* > > Steve Leyton, President > > T *|* 619.255.8964 x 102 *| * www.protectiondesign.com > <https://linkprotect.cudasvc.com/url?a=http%3a%2f%2fwww.protectiondesign.com%2f&c=E,1,9CKe5aPIcGnxTh3rNyKOt2U2-GOVvOdw2Xz6vrR2MqYZvk91evpKrBN_6N8qNRe1B3kiOZCbkbjBqLE-DX1GN4lCqfbOWJ5BR_PvnK2SRu_6FJAC41yjT66ACFw,&typo=1> > 2851 Camino Del Rio South *|* Suite 210 *|* San Diego, CA 92108 > Fire Protection System Design *|* Consulting *|* Planning *|* Training > > > > > > > > > > > > > > > > *From:* Micah Davis <[email protected]> > *Sent:* Monday, September 25, 2023 8:55 AM > *To:* SprinklerForum <[email protected]> > *Subject:* [Sprinklerforum] Standpipe PRV Question > > > > Good morning, Forum! > > > > I've got a head-scratcher and am interested in the Forum's collective > opinion! Important project parameters are as follows. > > > > - 42-story high rise with an automatic standpipe > > - Seismic Design Category - C > > - IBC 2018 > > - Fire pump supplied by city water supply > > - Secondary supply, as required by IBC 403.3.3, is a tank of adequate size > > - 305 psi @ 1000 gpm pump sized based on the feed from tank > > - Direct-acting pressure reducing valves on each floor > > > > Here is my issue. If I base my PRV settings on city supply, I cannot get > 100 psi at the remote valves when calculating tank as supply. If I base my > PRV settings on tank supply, I am over 175 psi discharge on the valve when > calculating city as supply. If I try to get my settings using the city as > static and the tank as residual pressures, there is no PRV setting that > works. > > > > I have my opinions about what I think should happen here, but I want to > see what the Forum thinks. I will not bother the group with what the > design team is suggesting I do. > > > > Micah Davis > > Ferguson Fire Design > > [email protected] > > > _________________________________________________________ > SprinklerForum mailing list: > https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org > <https://linkprotect.cudasvc.com/url?a=https%3a%2f%2flists.firesprinkler.org%2flist%2fsprinklerforum.lists.firesprinkler.org&c=E,1,JipD_jEQYtMK3MwRqZDS7PUm4_IGCwXD8Y7HS5azUbR8W-sCg9S1HTo90qI_P00BwX2UZ_ThA1YT6XmkUc5J1mssnAMYlQuSZQ0-gqZKwgp-VRYYIqdYTU47uw,,&typo=1> > To unsubscribe send an email to > [email protected] > > > _________________________________________________________ > SprinklerForum mailing list: > https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org > To unsubscribe send an email to > [email protected] >
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