As per std 8.2.1 on NFPA 13 it indicates an area of 3720m^2 per control valve, this works out to be 400 sprinklers per control valve.
NFPA 13 is not define the number of nozzles, if you do your own rough calculation base on the maximum area per nozzle you will get the number around 400. But if the project it's related with some insurance company, they are interested in the area not the number of nozzles, because in case of changes in the system or the system to be out of function, they want to be sure that bigger area of 3720 m^2 will be not out of function.
As well this is the reason why NFPA 13 make limitation per valve.
In an area that exceeds 3720m^2 would you then use two control valves?
Yes, especially if the project is related to the insurance company supervision. Because they often check this and every time they remind you to check the size.In any case, it's good to be inside the boundaries of the standard.
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