## Design criteria for and extra hazard room of 96 sq.meter

## Design criteria for and extra hazard room of 96 sq.meter

(OP)

I am new to sprinkler design.

Can you guide me how to do a hydraulic calculation for an area less than the minimum required area?

For example, for Extra Hazard group 2, min density and area =232m2 @ 16.3 mm/min. Consider my room is 96 m2. What will be the minimum flow for an area of 96 m2 ?

The below is from NFPA. Can anyone explain to me? I could not follow it. As per my understanding, Step 3 will always be greater than 0 and I didn't understand the rest of it.

23.4.4.2.4* Where the available floor area for a specific area/

density design criteria, including any extension of area as required

by 11.1.2 and Section 12.3, is less than the required

minimum design area, the design area shall be permitted to

only include those sprinklers within the available design area.

A.23.4.4.2.4 The following steps outline the procedure for

calculation in accordance with 23.4.4.2.4:

(1) Calculate the hydraulic design discharge including those

sprinklers within the available floor area.

(2) Calculate the minimum required discharge by multiplying

the required design density times the required minimum

design area.

(3) Subtract the discharge calculated in Step 1 from the discharge

calculate in Step 2.

(4) Where the discharge calculated in Step 3 is greater than 0,

the hydraulic design discharge is recalculated including

an additional flow equal to that calculated in Step 3. The

additional flow is added at the point of connection of the

branch line to the cross main furthest from the source.

(5) Where the discharge calculated in Step 3 is less than or

equal to 0, the hydraulic design discharge is as calculated

in Step 1.

Regards,

Ajit Jose

Can you guide me how to do a hydraulic calculation for an area less than the minimum required area?

For example, for Extra Hazard group 2, min density and area =232m2 @ 16.3 mm/min. Consider my room is 96 m2. What will be the minimum flow for an area of 96 m2 ?

The below is from NFPA. Can anyone explain to me? I could not follow it. As per my understanding, Step 3 will always be greater than 0 and I didn't understand the rest of it.

23.4.4.2.4* Where the available floor area for a specific area/

density design criteria, including any extension of area as required

by 11.1.2 and Section 12.3, is less than the required

minimum design area, the design area shall be permitted to

only include those sprinklers within the available design area.

A.23.4.4.2.4 The following steps outline the procedure for

calculation in accordance with 23.4.4.2.4:

(1) Calculate the hydraulic design discharge including those

sprinklers within the available floor area.

(2) Calculate the minimum required discharge by multiplying

the required design density times the required minimum

design area.

(3) Subtract the discharge calculated in Step 1 from the discharge

calculate in Step 2.

(4) Where the discharge calculated in Step 3 is greater than 0,

the hydraulic design discharge is recalculated including

an additional flow equal to that calculated in Step 3. The

additional flow is added at the point of connection of the

branch line to the cross main furthest from the source.

(5) Where the discharge calculated in Step 3 is less than or

equal to 0, the hydraulic design discharge is as calculated

in Step 1.

Regards,

Ajit Jose

## RE: Design criteria for and extra hazard room of 96 sq.meter

Let's say you are calculating a typical retail space for 0.2/1500. I have NEVER seen the required flow be exactly 300 gpm. There is over-discharge inherent in any system.

So, you could have a 1033 sq ft area at EH1 density that has a significant over-discharge to get a minimum of 600 gpm so you don't have to figure additional flow. If your flow in the area is less than 600 gpm, then you must add the difference at the end of the main in the area.

I am assuming EH1 and high temp or K11.2 sprinklers so that you can reduce the design area to 2000 sq ft.

Travis Mack

MFP Design, LLC

www.mfpdesign.com

"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...

## RE: Design criteria for and extra hazard room of 96 sq.meter

But I have a question here too. How do we practically include the extra flow to reach minimum required? Do we just consider the far end of main open and add a flow requirement of the difference with whatever pressure is calculated on that node? Similar like adding hose demand at the base of riser?

## RE: Design criteria for and extra hazard room of 96 sq.meter

step 1: Design discharge= 1033 x 0.4= 413.2 gpm

step 2: Minimum req. discharge= 2000 x 0.4= 800 gpm ( Considering k= 11.2)

step 3: step 2 - step 1= 800-413= 386.8 gpm

step 4: 413+386.8= 800 gpm

The additional 386.8 gpm is added at the point of connection of the last branch line on the cross main.

If I have only 4 sprinklers on the last branch line. I need to consider the above additional flow at this point.

In such a case, the pipe size on the last branch would be at least. 3 inch( 80 mm ) while the other branches lines are smaller.

In addition to this, for a room of small size such as this, the cross main size would be quite big.

I hope I have done the steps correctly. Eventually if we need to calculate with 800 gpm itself, I don't understand the use of all these steps given by NFPA and what is the point of adding the flow at the last branch.

I am just asking from the procedural point of view set forth by NFPA and trying to understand the practical approach to the problem.

I have another question.

If my room volume= 96 m2 x 3 m Height= 288m3= 76081 gallons

Now, if as per design 800 gpm is discharged for 60 minutes then the volume of water @ 60 min= 48000 gallons. Won't this discharge flood the entire room.

I mean I don't get the logic.

Please help.

## RE: Design criteria for and extra hazard room of 96 sq.meter

## RE: Design criteria for and extra hazard room of 96 sq.meter

1033 sq ft * 0.4 is THEORETICAL. If you calc it out based on actual discharges and pipe sizes, then you will have something in excess of your 413.2 gpm. You may be closer to 500 or 600 gpm. So, you are only adding the difference in it. But, you add it at the main. All of the branch lines will still be the same size.

Travis Mack

MFP Design, LLC

www.mfpdesign.com

"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...

## RE: Design criteria for and extra hazard room of 96 sq.meter

So, in reality we don't have to do all these steps. We just take the minimum design area @ density irrespective of the room size however small or big it may be. Then, theoretically, I have to size the pipes of that room to discharge @the calculated demand. In my case, I will have to design piping of 16 sprinklers to discharge @800 gpm (plus the hose demand)

Speaking of hose demand, what does the combined inside & outside hose stream allowance mean? Does it mean hydrant and indoor hose rack usage?

## RE: Design criteria for and extra hazard room of 96 sq.meter

Design your 16 sprinklers to provide your density per the occupancy required. Then, if you are less than the minimum of density x area, you add the difference at the end of the main in that area.

You still have to include your hose allowance where ever it is required.

Travis Mack

MFP Design, LLC

www.mfpdesign.com

"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...

## RE: Design criteria for and extra hazard room of 96 sq.meter

So, can we assume another hazard of EH1 in the same facility, Assume k=11.2.

Now, demand = 2000 X .30= 600 GPM. For the sake of discussion consider actual hydraulic calculation gave 750 GPM.

As explained to me earlier, the actual demand for the earlier discussed area would come to around 600gpm. Consider I get the same in hydraulic calculation.

What is my consideration for the maximum demand?

Case 1- 1033sq.ft, EH2 which has 600 GPM demand

Or

Case 2- 2500 sq.ft, EH1 which has 750 GPM demand

Or Even though case 2 has higher value, we should consider case 1 as the maximum demand @ 800 GPM because it's EH2.

Which is correct?

Regards,

Ajit

## RE: Design criteria for and extra hazard room of 96 sq.meter

For pump pressure, you take which gives you the greater pressure requirement.

Also, with the 11.2k, you get the same benefit as high temp sprinklers. So, your design area of both would be 2000 sq ft. I think you are trying to do something that is beyond your experience and expertise level. At this point, you should probably hire a consultant that can assist you on your specific project. There just seems to be a breakdown in understanding here, and it may just be a language / cultural misunderstanding. I apologize if the misunderstanding is on my end.

MFP Design, LLC

www.mfpdesign.com

"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...

## RE: Design criteria for and extra hazard room of 96 sq.meter

You are right when you say its beyond my experience and expertise. I want to go beyond fire Detection which I currently do. I am trying to learn sprinkler systems by reading already designed systems, NFPA 13, and asking some designers whom I know. The information I get is bits and pieces and that's why I am missing out on major basics.

Can you give me a guide as to where I can get a systematic learning experience for getting by basics right?

Regards,

Ajit Jose

## RE: Design criteria for and extra hazard room of 96 sq.meter

What country/ state are you located in

## RE: Design criteria for and extra hazard room of 96 sq.meter

Regards,

Ajit Jose

## RE: Design criteria for and extra hazard room of 96 sq.meter

MFP Design, LLC

www.mfpdesign.com

"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...

## RE: Design criteria for and extra hazard room of 96 sq.meter

Regards,

Ajit Jose

## RE: Design criteria for and extra hazard room of 96 sq.meter

https://ceatpd.okstate.edu/content/fire-protection...

Full disclosure: I'm a graduate of the program so I have a bias.

## RE: Design criteria for and extra hazard room of 96 sq.meter

That's good. If you are a graduate you can tell me if the online courses are good.

For starters, should I consider taking the below course.

Link

Basic Principles Of Automatic Fire Sprinkler Protection

Required Textbook:

Fire Detection and Suppression Systems, 4th edition, ISBN: 978-0-87939-398-4

Regards,

Ajit Jose

## RE: Design criteria for and extra hazard room of 96 sq.meter

I can't advise you on the quality of the online classes because when I was in college we didn't have on-line classes. But I passed (with high marks) one of three classes on water based fire protection systems at Oklahoma State University and an earlier edition of this book was used. You should also consider taking the course on fire protection hydraulics - it's very rigourous.