Misc Storage in Light Hazard Occupancy & Minimum Safety Factor

[ThePeck]

This is more of a rant but would like some insight into this from the outside.

AHJ - Florida city
Code - NFPA 13, 2016 & FFPC 7th Ed. 2016 (Florida Fire Prevention Code)
Building - Eye Care Center (Doctors Office)

First of all, Florida requires all requirements by the local AHJ that are not stated in 13 or the FFPC to go through an adoption process where it's brought to the state fire marshall. These are public information maintained by the state. So first off the local AHJ is requiring a 10psi safety factor, which aggravates me. I know we typically roll over and give them what they want because fighting it is usually too much of a process.

So the building is entirely Light Hazard except for a single room labeled as storage. Which is located in our remote area. They make a comment about needing OHII hydraulic calculations if it's storage. So we go ahead modify the plans and flow the 2 heads in the storage room as OHII which drives the entire system producing an OHII demand in a Light Hazard calculation. Which left a 3psi safety factor. It was only after that when we found out they also required a 10psi safety factor. We "discuss" this with the plans reviewer insisting it's not required and that there's already so much safety built into it since the 2 heads in the storage room are driving the entire thing. We still end up having to run 2 separate hydraulics. One light hazard without the storage rooms included with a 15psi safety and the OHII with only the 2 heads in the rooms ended up being a 42psi safety. The pipe size, location, or routing didn't change just the design area setups.

It's kind of amazing to me that some reviewers are so blinded to requiring a certain safety factor. Or that they feel they can demand a certain safety factor that isn't required by NFPA code or the state fire code. And without going through the adoption process the state requires. Maybe I'm wrong on it but requiring something above and beyond code would require the state's approval. I know insurance companies require more but they are kind of the AHJ when it comes to their insured properties. Plus typically it's above and beyond code that satisfies the city/county requirements, i.e. FM.

What I kind of wanted to get at most was the handling of isolated "storage" areas in otherwise Light Hazard occupancies. There's 20.6.1 which allows it as long as you meet the requirements it states.

 

[TravisMack]

It sounds like you are trying to use the room design method for the OH2 closet. Does that closet have a 1 hour rated wall? What about rated door and self closer? if not, the calculation with just the 2 sprinklers flowing is not in accordance with NFPA 13.

It is not uncommon for a storage closet to drive the calcs, especially when at the end of the building in the calc area. Could you have done K8 sprinklers and dropped the start pressure closer to 7 psi. That would likely keep the start pressures of that area from driving the calculated areas.

I do get your issue of isolated storage in an otherwise light hazard bldg. I would like to think there is a better way to address this somehow.

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

http://www.mfpdesign.com

 

[MGXFP]

Add more sprinklers to the storage room to drop the end head pressure so it matches the pressure of the light hazard sprinklers. If the storage rooms are small you can omit the sprinklers from the calculation if you do not take remote area reductions and calculate the 1,500 sq.ft. I don't think you can use the room design method unless all the requirements of 13 are included and from your results above, the storage room does not produce the highest demand. As Travis stated, increasing the K factor of the sprinklers in the closet would also drop your head pressure.

Many jurisdictions have adopted IBC, NFPA etc with amendments and a 10 psi safety factor is not uncommon. Many of your plan reviewers are simply trying to check all the boxes on their review checklist before moving onto the next set of drawings. Personally i always try to get to know the plan reviewers which usually makes the process smoother.