2" DN50 NPT 2 Way 12VDC 9-24VAC/DC Stainless Steel Normally Closed Electrical On/Off Motorized Ball Valve

I'm writing this shortly after installation, so I cannot testify to the longevity of the valve. However, first impression is good. The range of voltage and also accepting both AC/DC is unusual. I checked out the operation using a simple 9 volt battery and it operated many times in succession, nice and quiet taking a few seconds to cycle. My ammeter shows that it draws a small current when in the open position ( mine is a normally-closed valve), but of course none in the closed position. It is spring-return (internal, can't see the spring) which is my only concern over time if the ball gets crudded up with hard water scale. It has an indicater on top showing the valve position. An added feature is there are internal limit switches which, using a common and two signal wires, will pass through a low voltage signal indicating closed or open. The stainless steel valve body is nicely manufactured. There are no directions with the unit other than a wiring diagram on the box and a similar label on the unit. So in the picture you can see a blue/white "button" which can be turned and has "F" and "S" arrows on it. I do not know what this is for, tried turning it one way or the other to see if it affected cycle time (assuming "F" = faster and "S" - slower) but could discern no obvious difference. An explanation of this would be helpful. This is mid June 2017, we'll see how this works over time and if need be I'll edit this review.