If power is shut off to a solenoid valve and it opens, what type of solenoid valve is it?

A solenoid valve that opens when power is shut off is classified as a normally open solenoid valve. This type of valve is designed to remain open when there is no electrical current supplied to the solenoid, allowing the fluid to flow through the valve. When power is applied to the solenoid, the valve closes, creating a shut-off function.

In contrast, a normally closed solenoid valve would remain closed without power and only open when the solenoid is energized, which does not fit the scenario described in the question. Automatic and manual solenoid valves refer to different operational modes rather than the status based on power supply, adding further distinction to the classification of solenoid valves.

Thus, the correct identification of a normally open solenoid valve aligns with its operational behavior in response to electrical power, confirming that the solenoid valve opens when the power is cut off.