Sprinkler Criteria with Group A Above Class IV?

2/4/2022

For low-pile/miscellaneous storage, NFPA 13 has Group A protection up to 5-ft in height requires Ordinary Hazard Group 2 criteria. It also requires Class IV up to 12-ft as Extra Hazard Group 1.

Could you, theoretically, design for Extra Hazard Group I, but put the Group A in the 7-12ft range with Class IV below?

There would be no commodities above the Group A plastics, but I'm not sure that the Class IV would be protected throughout properly.

Thanks in advance.

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10 Comments

Pete H

2/4/2022 07:15:41 am

I'd be leaning on no. I think the added elevation of the group a plastics would put you in EH2.

Now what gets me is this was easier to answer when 2013 edition of NFPA 13 was the most known standard, because they used to define height for storage a bit more clearly as "above the floor":

NFPA 13 (2013 Edition)
3.9.1.1.* Available Height for Storage - The Maximum height at which commodities can be stored above the floor and still maintain necessary clearance from structural members and the required clearance below sprinklers

*The annex for this entry from this edition reinforces this further.

-

But they took that out in 2016.

Chris Nelson

2/4/2022 08:24:12 am

This is actually my question. Thank you for your response Pete! I see where you would call out the EH2, but that would only be applicable for miscellaneous storage as only 5ft is allowed in "low piled storage" in accordance with NFPA 13 13.1.1(6) which is where my question is really trying to answer. The handbook does point to that fire characteristic take on those of the higher commodity but thats where it get me with the OH2 vs EH1. In any scenario we expect the Group A to become involved rather quickly, but my thought was that the EH1 would quickly extinguish the Group A as we have 0.3 vs 0.2 gpm/sf and then handle the Class IV throughout as required in the table though extinguishment time would be expected to be lengthened.

Let me know your thoughts!

Pete H

2/4/2022 09:05:41 am

Good pick up on 13.1.1(6).

Actually then, I'd say you're in chapter 17 (if there are open racks).

Which can kind of work in your favor (moving to 2016 edition):

17.2.1.3. - For storage of Group A plastics between 5 ft and 12 ft in height, the installation requirements for extra hazard systems shall apply.

At this point, I'd need to know more about the storage arrangement to give an accurate answer or thought though.

2/4/2022 08:17:37 am

This is addressed in NFPA 13, 2016 chapter 5 section 5.6.1.2.3. The handbook (page 107) has a research note that talks about this also

Chris Nelson

2/4/2022 08:28:07 am

Mixed commodity 5.6.1.2.3 is actually the path that I took for my project as it was the most conservative. But since the Group A only requires OH2 but is only up to 5ft and the EH1 is for Class IV up to 12ft. My question is more for is "up to 5ft" allowed in any point in space and if its allowed to be applied when storage above other commodities.

Franck

2/4/2022 08:54:32 am

If you put Group A commodity with Class IV (imagine Group A from ground to 5 ft and class IV above), it may ends up that all is to be considered as a Group A commodity.
Remember that a Group A commodity can be a class IV with a certain amount (% or weight) of plastic within.

The other thing is that the rule of one day may be forgotten tommorrow. If you can store up to 12 ft and give the information "please do not store plastic above 5 ft", can you be sure that you will NEVER EVER have plastic above 5 ft ?
Even temporarily ?

Your assumption would work only if you store plastic up to 5 ft (with nothing above) and class IV up to 12 ft in other racks.
In that case, you can protect your entire building with EH1 that would cover your 5 ft plastic and your 12 ft class IV.

Chris Nelson

2/4/2022 09:49:26 am

I completely agree and my company generally "baby this client" to prevent them from forgetting how we need them to store things, which is why I went with the mixed commodity allowance of chapter 5. The whole "don't put group A next to each other" is easier to police than my thought process of keeping group A only in the7-12ft range of a rack.

I want to see if theoretically you could police Group A to the 7-12ft range of a 12ft top of storage rack protected to class IV protected rack due to the EH1 vs OH2 requirements.

Franck

2/4/2022 03:10:37 pm

If you have class IV from 0 to 7 ft and then group A from 7 to 12, it would be worse than class IV from 0 to 12 and EH gr 1 is not sufficient.

Jesse

2/4/2022 09:01:09 am

No. We protect the "overall" commodity class, not just the most prevalent commodity class. The 2016 version of 13 kind of changed how we determine that.

You may have a rack storage warehouse with DRR storage of predominantly C-III to 15-feet. But within that C-III, you have 20% of Group A. The overall commodity becomes Group A. Your scenario creates effectively 12-ft storage of Group A, and it needs to be protected as such.

Shaunna

2/4/2022 10:46:04 am

13.1.1 calls out and separates Miscellaneous storage of Group A plastics up to 12' in height.
We cannot overlook the definition of misc storage. I see folks frequently site "make sure you store your plastic under 5' " and all is good.
Misc storage:
Does not exceed 1000 sq. ft. in 1 pile area
Is incidental to another occupancy use group
Not more than 10% or 4,000 sq. ft. whichever is greater of the sprinklered area
Separate from other storage by 25'.

Then as allowed under 13.1.1 also:
Storage (not misc storage) of Group A plastics up to 5' in height as directed by 15.2.1 and 17.2.1.1

So first determine, do you have misc storage? If not use 15.2.1 and 17.2.1.1

Page 62 of the NFPA13 2016 Edition discusses this further.

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Sprinkler Criteria with Group A Above Class IV?

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