Carrol,
Hopefully, you caught Ron's reference to 11.3.1.2 and not solely the
requirement for a 20x20 spacing. Specifically, take a look at Ron's inferred
reference to 11.3.1.2 item number 2:
11.3.1.2* Unless the requirements of 11.3.1.3 are met, the minimum required
discharge from each of the four hydraulically most demanding sprinklers shall
be the greater of the following:
(1) In accordance with minimum flow rates indicated in individual listings
(2) Calculated based on delivering a minimum of 0.1 gpm/ft2 (4.1 mm/min) over
the design area in accordance with the provisions of 8.5.2.1 or 8.6.2.1.2
Item Number One requires us to examine the listing. The sprinkler listing for
a residential sprinkler likely delivers .05 gpm/sq ft (or just a bit more) and
do not try to "back in" to this density because it is based on a listed area of
20 x 20 in your case because you are 10 feet off the wall. This means the
listing requires 20 gpm or a little more.
Item Number Two says to use regular spacing requirements and deliver .10
gpm/sqft. The question is whether or not the "design area" is the SxL
rule(8.5.2.1) or the "Small Room Rule" (8.6.2.1.2).
IF (and I mean IF) your room meets the definition of a "small room", then you
may divide the room by the number of sprinklers and deliver .10 gpm/sqft over
THAT "design area". This would meet the requirements of 11.3.1.2, item number
two. In the example you have given to us, you would be able to flow .10 gpm
over the 256 sq ft of "design area" if your room meets the definition of a
small room. The flow from the sprinkler would need to be a minimum of 25.6 gpm
under this method.
The last step is to compare the flows required by Item One and Item Two. This
is called for in the charging sentence of 11.3.1.2 ("shall be the greater of
the following"). That would mean that your sprinkler must flow the greater
of the listed flow of 20 gpm or the "design area" flow of 25.6 gpm. Therefore,
your sprinkler must flow 25.6 gpm!
Now go rock on! And have your AHJ call Ron Greenman if he has any further
questions.
Sincerely,
A SprinklerGeek named Cecil
> Date: Sat, 30 Oct 2010 09:49:29 -0700
> From: [email protected]
> Subject: Re: Residential "Room Design Method"?
> To: [email protected]
>
> That was exactly what I was hoping to hear. Now, hopefully, I can convince
> the
> AHJ of this. I have INCREDIBLE pressure and flow and it seems crazy that I
> can't get 4 heads to flow.
>
>
> Thanks everyone!
>
> Carrol
>
>
>
>
> ________________________________
> From: Ron Greenman <[email protected]>
> To: [email protected]
> Sent: Sat, October 30, 2010 9:25:04 AM
> Subject: Re: Residential "Room Design Method"?
>
> 2007/11.3.1
>
> see
> 11.3.1.1
> and
> 11/.3.1.2
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