Combined System Calculation Basics

[NewFPeng]

Hi
I'm new at fire protection system design, and I have some questions.

The following is some information about my system:
Type: Combined system.
Water Supply: On-site pump
Occupancy: Light Hazard (7 floors)
Water Supply: ON-SITE tanks and pump arrangement.

My most important question is: When calculating the water supply required for this system do we assume that the sprinkler system and the standpipe system will operate simultaneously and thus design the system to accommodate both? Or maybe the sprinklers and the inside hoses?


Supposedly they are not assumed to operate simultaneously, my understanding so far is the following:
1- I calculate the system to meet the NFPA 14 regulations regarding the water supply and the pressure required for the most hydraulically remote hose and thus I have a gpm and psi values that my pump has to meet.

2- I calculate the sprinkler system down to the pump and see whether the sprinkler system requirements exceed those of the hose system. Usually the sprinkler demand will be less than that of the hose demand. If that is the case then then my work is done.If the sprinkler demand is higher then my water supply has to meet the sprinkler demand. I am talking here about the supply GPM and PSI. It is a given that that the tank must hold enough water for both systems.

Is this methodology correct?


My other question is this: Under table 11.2.3.1.1 NFPA 13 there is a part about inside and outside hose. What exactly are these two hoses? Are these two hoses (1.5" and 2.5") the hoses mentioned under the ClassIII in NFPA 14?


I greatly appreciate any answers to any part of my inquiry.

Thank you

 

[jkampana]

Correct, you do not have to add the sprinkler system demand to the standpipe demand. The only caveat being that if the flow demand for your sprinkler system is higher than that of your standpipe you must use the sprinkler demand value in your calculations instead.

For your second question, inside hose deals with 1 1/2" hose stations within a building, connected to your sprinkler system. If there are none, do not add an inside hose. Outside hose will be determined be occupancy classification.

 

[NewFPeng]

Thank you very much.