After careful deliberation and reflection on all the previous posts to this
thread, it seems to me we may be over-thinking the whole process.
Since the FDC is "supplemental" to the water supply and is not intended nor
required to provide a specifice flow, then the whole concept of where and how
to tie it in becomes a much more simple process.
(1) The FDC connection is a "Parallel" connection, and as such the water and
pressure provided is really nothing more than a MANUAL secondary supply.
(2) As a "Parallel" supply it will augment or assist the primary supply until
which time as the PRESSURE from the secondary supply exceeds the primary.
(3) Since it is a MANUAL supply, once the secondary exceeds the primary it in
effect BECOMES the primary, unless manually throttled back to balance the
primary supply pressure.
No real difference than (2) fire pumps in parallel.
(4) The FDC connection piping size only needs to be as large as the riser up to
the point it connects to the system piping.
If you calculate a system and need a 4" riser, but reduce the feed main to
3" from the top of the riser out to the system cross-main, then what does it
matter if the 4" FDC connection piping connects
to a 3" cross-main? The FDC connection piping, again, in effect, becomes a
4" riser (without the control valve) until it ties in to the sytem. (NO
DIFFERENCE)
(5) The new position of the NFPA technical committee to connect to cross-main
or feed-mains only (no branch-lines)was made, in my opinion, to alleviate the
inherent difficulties in overcoming extreme
pressure losses due to both friction and velocity in smaller sized piping,
(2" and smaller) when pumping higher flows at higher pressures, such as an FDC
would provide from a pumper truck.
(6) By limiting the connection to cross-main or feed-mains, the whole function
of the FDC secondary supply overcoming and then BECOMING the primary supply is
addressed, as you will not get the extreme
pressure losses at higher flows, as you would in 2" or smaller branch-lines.
(7) At any time the FDC supply pressure drops back below the original primary
supply pressure, the whole process reverts back to the origianl primary supply.
In my humble opinion, the NFPA standards relating to FDC connections, as
written, already address MOST all the scenarios and issues discussed this fine
Friday afternoon.
With a little more thought process and understanding of the function of the FDC
connection and its purpose, the whole point of "Where to tie it in", What size
it needs to be", "Why tie-in only on feed or cross-mains", etc, becomes a much
clearer picture.
One final thought... Is is quitting time yet ;-)
Ray Vance
Chief Engineering Tech.
Wayne Automatic Fires Sprinklers, Inc.
www.waynefire.com
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Fletcher, Ron
Sent: Friday, July 18, 2008 1:40 PM
To: [email protected]
Subject: RE: FDC Connection
Flow and pressure cannot be supplemented (boosted) given the valve arrangement
required by NFPA. The main riser check valve is either open or closed. The
handbook calls it an "auxiliary water supply" to the system. Supplementing the
automatic supply and increasing overall reliability. I have run into a lot of
AHJ's that think the FDC will add to the flow and pressure from the city supply
like a booster pump but it will not. The FDC becomes the sole source of water
and pressure when used.
Ron Fletcher
Aero Automatic Sprinkler
Phoenix, AZ
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Thom McMahon
Sent: Friday, July 18, 2008 9:59 AM
To: [email protected]
Subject: RE: FDC Connection
YES! SUPPLEMENTAL! As stated in NFPA 13, 2007 handbook A.6.8.1
You can do whatever you want thru those 2-2-1/2" connections, but somehow I
don't think they were ever intended to "Supply" the entire demand for an ESFR
40' warehouse, or a .3/3000 design area, or a large deluge at a refinery,
or--or---or--.
If you do that dangerous thing (use Logic) we should only rely on 2-2-1/2"
connections for up to 500 GPM. (See NFPA 14) Obviously you can, with the right
pumper, and the right hydrant, flow more than 500 at an elevated pressure. But
if it was the intent to "Supply" the entire system demand through the FDC, why
are we not required to prove it? With a hyd. Calc.
using the nearest hydrant and the smallest pumper or responding engine, and
appropriate hose and friction loss? You really want to go down that path?
Thom McMahon, SET
Firetech, Inc.
2560 Copper Ridge Dr
P.O. Box 882136
Steamboat Springs, CO 80488
Tel: 970-879-7952
Fax: 970-879-7926
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Fletcher, Ron
Sent: Friday, July 18, 2008 9:05 AM
To: [email protected]
Subject: RE: FDC Connection
Supplemental? If 150 psi is pumped into the FDC the riser check will close
making the FDC the only supply.
Ron Fletcher
Aero Automatic
Phoenix, AZ
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Thom McMahon
Sent: Friday, July 18, 2008 7:45 AM
To: [email protected]
Subject: RE: FDC Connection
I think it's important to remember that the FDC is "supplemental" to the
supply, not "Equal" to a supply. I feel that the 4" tied to the 2-1/2"
MAIN
meets the intent of the standard. It does not need to be 4" all the way from
the riser to the FDC, when the FDC is remote from the riser and connects to a
MAIN.
Thom McMahon, SET
Firetech, Inc.
2560 Copper Ridge Dr
P.O. Box 882136
Steamboat Springs, CO 80488
Tel: 970-879-7952
Fax: 970-879-7926
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Garth W.
Warren
Sent: Friday, July 18, 2008 9:38 AM
To: [email protected]
Subject: Re: FDC Connection
it should be 4" from the connection to the main and then connected through a
21/2x21/2x4 tee. I disagree that NFPA allows for connection anywhere on the
system, it states "provided the pipe size meets the requirements of 8.17.2.3."
Otherwise "creative" companies would have 1" fdc piping connected to the end of
a line.
Garth
----- Original Message -----
From: "Brian Harris" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Friday, July 18, 2008 9:02 AM
Subject: RE: FDC Connection
> The FDC is actually remote from the riser & ties into a 2-1/2"
floating
> main. I think it should at least be 4" all the way to the back main
and
then
> reduce it there....
>
>
> Brian Harris
> FDFP INC.
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of
> [EMAIL PROTECTED]
> Sent: Friday, July 18, 2008 8:48 AM
> To: [email protected]
> Subject: Re: FDC Connection
>
> NFPA 13, 2007, section 8.17.2.3, (3) - For hydraulically calculated
systems,
> the fire department connection shall be permitted to be less than
> 4 in. and no less than the size of the system riser, where serving one
> system riser.
>
> My opinion is that the pipe from the FDC itself to the riser needs to
be
4"
> minimum. Based on your description I would interpret that as saying
that
> the 2 1/2" pipe on the FDC is not permitted as the riser is 4" and I
am
> assuming the 2 1/2" reduction is between the FDC and the riser.
>
> My opinion only.
>
> Andrew Weisfield
>
>
>
>
> "Brian Harris" <[EMAIL PROTECTED]> Sent by:
> [EMAIL PROTECTED]
> 07/18/2008 08:36 AM
> Please respond to
> [email protected]
>
>
> To
> <[email protected]>
> cc
>
> Subject
> FDC Connection
>
>
>
>
>
>
> Forum,
> Quick FDC connection, I just saw on some drawings that came in that
the
> FDC
> is 4" with a 4" check valve and then reduced down to 2-1/2" with a
> reducing coupling. The system riser is 4", can you choke it down like
> that?
> Technically the FDC is the same size as the riser but where do you
draw
> the
> line? I'm not liking it, what say you???
>
>
> Regards,
>
>
> <http://www.firstdefensefire.com/>
>
>
>
>
>
>
>
>
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