I have a Zone Valve Question. I have hot water baseboard heat with 4 Zone Valves (White Rodgers). Just two days ago, the Living Room and Kitchen got extremely warm, I turned the thermostat down and it did not change the room temperature. I went to check the Zone Valve and it was "OPEN", I manually Closed the valve. When I did this, I noticed that it did not automatically go to the closed position, I had to move it manually all the way to the closed position. This is not the normal behavior. Obviously, this vale needs to be replaced.
My question is: Can the upper portion (just the exterior) of this unit be changed without making it necessary to drain the system?