“The purpose of a deluge system is to deliver sprinkler water coverage to the entire area of a fire in the least amount of time possible. It accomplishes this by admitting water to sprinklers or spray nozzles that are open at all times.
Because the sprinklers are of the open type, the deluge valve must be opened as signaled by a specialized fire alarm system. The type of fire alarm-initiating device (e.g., smoke detectors, heat detectors, or optical fame detection) is selected mainly based on the hazard. The initiation device signals the fire alarm panel, which in turn signals the deluge valve to open. Activation can also be manual, depending on the system goals. Manual activation is usually via an electric or pneumatic fire alarm pull station.”
Reference: (2011). Plumbing Engineering Design Handbook – A Plumbing Engineer’s Guide to System Design and Specifications, Volume 3 – Special Plumbing Systems – 1.3.4 Deluge Systems.American Society of Plumbing Engineers (ASPE). Online version available at: http://app.knovel.com/hotlink/pdf/id:kt00AE8D4H/plumbing-engineering-4/deluge-systems