Pressure for Class III Stand Pipe - NFPA

[Vusal Quliyev]

Dear Experts,
there is big confusing at the NFPA 14 to understand.

It is stated that for Class I:
maximum allowed pressure - 175 psi (12.1 bar)
minimum allowed pressure - 100 psi (6.9 bar)

It is stated that for Class II:
maximum allowed pressure - 100 psi (6.9 bar)
minimum allowed pressure - 65 psi (4.5 bar)

My question is about class III system. As you know Class III is combination of Class I and Class II.
So there is no any pressure value to apply class III to comply with class I and class II at the same time.
(If I choice 6 Bar it does not complies to Class I. If i choice 8 bar this time it will not complies to class II)
What is your recommendation?

 

[SprinklerDesigner2]

You go with the requirements of a class 1.

 

[Vusal Quliyev]

SprinklerDesigner2, thanks for your Help. Can you refer standard section for this information, please?

 

[UFT12]

How does your jurisdiction handle 1 1/2 connections on class III systems? Are you going to install hoses? You will need to study chapter 7 of 14 carefully. See specifically maximum and minimum pressure limitations and everything that deals with 1 1/2 connections.

 

[DavidCR]

It may be complemented with local or AHJ requirements.
You go with class III and maybe a removable restricting device on 1.5 hose connection or hose valve may solve the class II req.