So I have hot water heat. I was doing some pre season checks. System coldand off is at 12psi as set by the automatic fill. I have an isolation valve on my expansion tank with a drain so I can test bladder pressure. So here is where it gets strange for me. The system is cold and not running. I go to isolate the tank and drain after the valve to allow atmospheric pressure on the other side of the bladder. I test and adjust to 12psi air on expansion tank. But then I look on the boiler and the pressure has climbed to about 30psi water. I close the drain and open the isolation valve to the expansion tank and it drops back to 12. Now I just shut the isolation valve and the pressure slowly increases back up to 30. Open the valve and it drops back down.
So then I turn off the valve to water make up and then turn off the valve to the expansion tank and no movement. Then if I open the valve to the water make up the pressure rises again. But if I open the valve to the expansion tank it goes back to 12?
So then I turn off the valve to water make up and then turn off the valve to the expansion tank and no movement. Then if I open the valve to the water make up the pressure rises again. But if I open the valve to the expansion tank it goes back to 12?