Multiple FDC Sources 3

[bmlxd40]

I have a highrise building with the two FDC’s as specified in NFPA 14, 2013 ed., chapter 7.12.2. The FDC’s are two inlets each. This is in compliance with 7.12.3.3, even though the total standpipe demand is 750 GPM.

In some situations with a greater standpipe demand, we may have one FDC with a 6” piping connection & more than two inlets. We would still have the remotely located FDC with a 4” connection and two inlets.

My questions is:

When calculating to the FDC to obtain the required pressure at the FDC, should the demand be split with 500 GPM flowing through the most remote (Or smaller) FDC, and the other 250 through the closer (Or larger) FDC?

 

[TravisMack]

Isn't the requirement for multiple FDC locations based on the concept that one may be down during the fire event? If that is the case, then I would think you would calculate to just a single FDC.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[bmlxd40]

Travismack, that makes perfect sense to me, and I buy that 100% except that why would we calc 750, or even 1000 GPM through a 2 inlet, 2½"x2½?4" FDC?

I used to always design three or four inlet FDCs (One for each 250 of standpipe demand)on most high-rises until we discovered the 2013 edition added section 7.12.3.3 which allows us to now meet the requirements of 7.12.3 through multiple locations. So, we could legitimately have a building with a standpipe demand of 1000 GPM, but use two, 2½"x2½?4" FDCs remotely located. Obviously there is a significant savings in going that route, especially if long bulk runs are involved.

Thanks for your reply

 

[stookeyfpe]

The NFPA 14 requirement for two FDCs on a high rise fire is based on the 1st Interstate Bank fire in Los Angeles, CA in the late 1980s. While it's not explicitly stated, the design should assume that one FDC is out of service because the FD can't safely pump the system because of fire conditions. For a fully sprinklered building, each FDC should be designed for 1,000 GPM of flow.

During the 1st Interstate fire, glazing was failing on the side of the building that was involved in fire. The falling glazing was striking the hose lines supplying the FDC. The driver/engineer on the Engine company reportedly shielded himself by crawling under the apparatus. During the fire, he apparently replaced two or three sections of hose while the glazing was failing, and in one case was struck and injured. He continued his duties, was hospitalized, and if my memory serves me correctly, returned to duty but later retired with a medical disability as a result of the injuries.

 

[TravisMack]

Scott:

Thank you for the background on that. It helps to confirm the way that I have always done it. I won't fault anyone for trying to use the standard as it is written and interpreted, but I feel much better having it designed for a single one only being operational.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692