FDC & PRV 1

[jjmoore73]

I have 5 vertical fire sprinkler risers on the reduced pressure side of a PRV. FDC, Fire pump and standpipe are on the other side of the PRV. AHJ wants the FDC to split and supply both sides of the PRV. This does not make sense to me, is there a code requirement for this. I will strategically place check valves to accomplish this, but does anyone know why the FDC needs to be physically connected to both side of the PRV? Thanks - J

J. Moore
NICET III - Water Based

 

[cdafd]

What is the ahj's concern??? Not being able to pump enough pressure through the prv?

I would ask the question why

 

[skdesigner]

The issue is that NFPA 13-2013 8.16.1.2.4 states "A listed indicating valve shall be provided on the inlet side of each pressure reducing valve, unless the pressure reducing valve meets the listing requirements for use as an indicating valve."

Control valves in the FDC line are not cool. I would go so far as to suggest you probably need two separate FDC's - one for the high pressure side and one for the low pressure side.

 

[cdafd]

SK

Disagree somewhat , the same setup of control valves happens all the time, when there is a room of multiple risers and one fdc feeding them

Each riser would have a control valve after the fdc

 

[skdesigner]

NFPA 13-2013 8.17.2.4.3 For multiple systems, the fire department connection shall be connected between the supply control valves and the system control valves.

Each riser is allowed to have a control valve after the FDC, but is there allowed to be (1) supply control valve upstream of all the system control valves, that when shut, effectively prevents any fire dept water from reaching any of the 5 sprinkler systems?

I'm not a NICET III, just a joe blow designer, so I'm looking forward to learning something here.

 

[TravisMack]

I will have to try to find the exact section, but NFPA 13 or 14 states (or used to) that the FDC is to be connected on the system side of a PRV. My guess is that if they fail, I have heard that they fail closed.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[TravisMack]

He may be looking at NFPA 14, 2010 7.2.4 (7)

7.2.4* When system pressure-regulating devices are used in lieu
of providing separate pumps, multiple zones shall be permitted
to be supplied by a single pump and pressure-regulating de-
vice(s) under the following conditions:

(7) The fire department connection(s) shall be connected to
the system side of the outlet isolation valve.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[skdesigner]

T mack,

I heard that if they fail, they fail open (which I'm guessing led to the redundancy requirement of NFPA 14 7.2.4, specifically "Regulating devices shall be arranged so that the failure of any single device does not allow pressure in excess of 175 psi to more than two hose connections). Moot point though if you consider that NFPA 13 mandates a control valve on the supply side of the PRV, and you can't have a supply control valve between an FDC and the system control valves.

 

[TravisMack]

Yeah. I am sure they can fail both ways. I would think it makes sense to fail open for the reason that you stated. However, I have never known one in service to fail so I really have no experience either way. But, NFPA 14 is pretty clear that the FDC is to be downstream of the PRV when you have a low and high zone.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[cdafd]

If you have a multi story building with a prv on upper floors are you going to pipe the fdc supply to each floor and tie in after the prv

http://www.firesprinkler.org/sprinkleragesite/sprinklerage.cfm?id=562

 

[skdesigner]

No, because then the PRV control valve would be the system control valve, not the supply control valve.

 

[Duwe6]

FWIW - pressure reduction valves usually fail open. Usually.

 

[stookeyfpe]

FWIW - pressure reduction valves usually fail open. Usually.

As someone who has worked a number of high-rise buildings, pressure reducing valves can fail in the open or closed position. When they fail in the closed position, the firefighters abandon the valve and find one that is working. It's very frustrating. We haven't experienced a PRV failure on a sprinklered floor (yet).

 

[3cio]

Hi guys,

Kindly refer to NFPA-14 Figure A.7.2.4.


hope it helps,