I’ve had some large demand systems….5000 gpm and more. They always had specified (3) 2500 gpm pumps for the 5000 gpm systems. I had one 9000 gpm system that had (4) 3000 gpm pumps. The idea was that if any one pump was done, the system would still be maintained with adequate pumping capability.
I had a pump rep try to explain it that the systems had requirements of a backup pump. It was less expensive to provide (3) 2500 gpm pumps than (2) 5000 gpm pumps. And, you technically had a backup. The idea is that it would be very very rare to have 2 pumps down simultaneously. Thankfully, I’ve only been involved on the shop drawing side of these where others have already determined the pumping capacity and how it was to be delivered. From: Sprinklerforum [mailto:[email protected]] On Behalf Of Mark.Phelps Sent: Tuesday, December 19, 2017 7:17 PM To: [email protected] Subject: Re: [EXTERNAL] Multiple Pumps Other NFPA Standards address fire pump requirements such as 409 and 15 I believe as requiring the full satisfaction of the design demand being met with the largest (of multiple pumps) being out of service. I've not experienced such high flow demands as Q= 7500 outside these Standards. Mark at Aero 602 820-7894 Sent from my iPhone On Dec 19, 2017, at 4:05 PM, Cahill, Christopher <[email protected] <mailto:[email protected]> > wrote: So I found this in NFPA 20 - 4.9.1 A centrifugal fire pump for fire protection shall be selected so that the greatest single demand for any fire protection system connected to the pump is less than or equal to 150 percent of the rated capacity (flow) of the pump. So does that mean if the demand is 1,000 gpm I can’t use 3 - 250 gpm pumps? Don’t ask why someone would do that, yes it would be odd. Think really big flows and high pressures where variable flow in reality one might choose to split the pumps. So basically isn’t it demanding a single pump for systems up to 7,500 gpm? (assuming a 5,000 gpm pump is the maximum) No option for using 2 - 3,000’s? Chris Cahill, PE* Associate Fire Protection Engineer Burns & McDonnell Phone: 952.656.3652 Fax: 952.229.2923 <mailto:[email protected]> [email protected] <http://www.burnsmcd.com/> www.burnsmcd.com *Registered in: MN If Americans switched from pounds to kilograms there would be mass confusion. _______________________________________________ Sprinklerforum mailing list [email protected] <mailto:[email protected]> http://secure-web.cisco.com/19AwbBeqFZF_Qn53w9ForKnuINbkAiy4_Q4UNbzQzVqJXb-RQmGlMrerjeZ56r_17EGJk_l2JUn4Ht5Je-G-8TrxjFJgJglAom2wxSjk5pPn4VD_8m4Qwuda3DTLpEWksjWvftiCCZqB1Hgv77GGInu8CRCVUUHAFboEShiQ4224xaYbfK_J-G6a0atr_V98O0urbIOYIOOqTzX_O4X-ZstYYiekNui26Xi9RoD0havaMmI3G0p1qRCowGeTp6Zvk/http%3A%2F%2Flists.firesprinkler.org%2Flistinfo.cgi%2Fsprinklerforum-firesprinkler.org
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