Asco 1/2" NPT, 240 volt, normally closed, brass-body solenoid valve for 15 lb. steam service with a maximum temperature of 250°F. Asco solenoid valves are activated by a solenoid (electromagnetic) coil, which when energized or de-energized moves the core (or piston) to apply pressure against its diaphragm and seat. There are two operations of these valves, either normally open or normally closed. Normally open valves allow flow throughout the valve until the coil is energized to close the valve. Normally closed is sealed until the coil is energized to open the valve. Maximum operating pressure refers to the maximum difference in pressure between the inlet and outlet.