FDC location on grid fire sprinkler system? 3

[cupcars]

I have a small 13,000 sqft rectangle non-combustible single story building. The single light hazard 2" wet system riser is in the back (south side) of the building. I have a 2" primary main running east & west at the back of the building fed from the 2" riser and a floating 2" secondary main running east & west at the front of the building. The branchlines (running north & south) between them are all 1 1/4" sch 40 with 1 1/4" riser nipples ( no out riggers). The branchlines are 75' long. The grid system is hydraulically calculated with a large safety factor.

The FDC is located on the front of the building. It is a single 2 1/2" connection fed with 2" pipe from the secondary 2" main.

To be clear - all mains, wet riser, and FDC feed piping are 2" sch 40. All gridded branchlines are 1 1/4" sch 40.

NFPA 13 (2019 Handbook) 16.12.5.1 states that a single wet system can have the FDC attached to any point of a feed main or cross main in the system provided you use the required pipe sizes. It also states the FDC connection not be attached to branchlines.

It does not call out any exceptions for a grid system.

The problem I'm having is the Fire Marshal says I have to tie the primary & secondary mains together with 2" pipe because the 1 1/4" branchlins are not big enough to get water to the primary main from the FDC. Or I could have made on of the branchlines 2". He saying that I'm interpenetrating the codes incorrectly and the codes would not allow a remote FDC be attached to a secondary main of a grid system.

Who is right?? How do you interpret these codes?

Thank you for the help.

JC

 

[UFT12]

Since you are connecting on a main which is the same size as the riser and it is the largest of the system, there should be no problem. Although smaller, the branch lines are typically many and should be able to provide the required capacity. See definition of 3.3.206.5 and A.3.3.206.5 with its commentary showing clearly the function of the branch lines in this case. At the end, if he is feeling comfortable with supplying the far main through the branch lines, why not feeling the same way vice versa through the supply of the FDC?

 

[cupcars]

Thank you for your reply!
There are 14 - 1 1/4" branchlines.
The total length of 2" main piping (east to west) from the first branchline to the last is 138'-0"

We tried explaining how the multiple branchlines feed each main. And that this grid works hydraulically (2 calc area's).

I don't have a subscription to NFPA or I would ask them for a ruling.

Thanks again for the help.

JC

I also tied the primary & secondary mains together at the ends with 2" pipe, then revised the Hydraulic Calculations. Area 1 gained .01 psi on the safety factor and area 2 gained .02 psi....

 

[cdafd]

So what NFPA 13 section is he referencing saying not allowed?!

 

[cdafd]

You might ask nfsa, even if not a member

https://nfsa.org/2020/08/04/nfsa-sprinkler-questions-ask-the-expert-of-the-day/

Suggest send question to field rep, to submit

https://nfsa.org/field-ops/

 

[cupcars]

When he said our setup was unacceptable, he was sent these references out of the 2019 NFPA 13 Handbook (See link)

 

[cdafd]

Not following the FD logic either


If you can get Stookey to reply, would go with what he says

 

[cdafd]

Cup cars,,,

Can you post a link/ picture/ other to your layout, to include where you want to tie in the fdc

 

[cupcars]

Attached pdf of hand drawn schematic of grid system.

 

[TravisMack]

He is simply incorrect. You can tie in the FDC to any main as you indicate. The FDC is supplemental and not primary supply in a fire sprinkler system. If you really want to show him, run a calc on the system using the FDC as a supply in your configuration. Since you have such small piping, I'm assuming a low water demand. You could calc with 200 psi at the FDC and let him know he is quite unreasonable.

But, he is not reading NFPA 13 correctly. You can attach to any riser, feed main or cross main. Look at Chap 3 for definitions. You have attached to a cross main.

Travis Mack, SET, CWBSP, RME-G, CFPS
MFP Design, a Ferguson Enterprise

http://www.mfpdesign.com

 

[stookeyfpe]

The calculation should be based on a 165 PSIG pressure. Realistically, unless the FD carries am inline pressure gauge, and the building is not a high rise, 150 PSIG at the FDC works every time.

 

[cupcars]

The AHJ questioning the FDC tie-in location contacted NFPA who informed them that the FDC location (tied into secondary main) was acceptable per NFPA 13 Requirements.

Thank you all for your help and responses!