An automatic irrigation valve is either normally closed (NC) or normally open (NO). The difference is what the valve does when it has no power.
- A normally closed valve needs power to open. Lose power and it springs shut.
- A normally open valve needs power to stay shut. Lose power and it springs open.
Why it matters
With normally open valves, every power cut, controller reboot and firmware update floods the farm for its duration. An overnight outage empties the tank onto the crop. In Kenya, where power cuts are common, that is not a hypothetical.
A normally closed valve fails shut, which is the safe direction: the crop misses a watering, but nothing floods and no water is wasted. On a new install there is no reason to accept anything else.
Beyond the valve
Good automation adds more fail-safes on top. Our field valves close themselves if they lose contact with the platform for ten minutes, and refuse remote firmware updates while open, so a reboot can never strand a valve mid-irrigation. Every manifold also keeps a manual bypass.