I recently had to change the expansion tank on our boiler. I decided to add a shut off with drain as well as a pressure gauge to make it easier going forward.
I've come across a problem. The pressure gauge I installed shows 12 psi when cold and 15 psi when hot. I was under the impression it was meant to stay at 12 even when hot? Which is even more weird is the pressure gauge on the actual boiler is showing higher psi.. around 18 cold and 22 when hot?
The only thing I thought might cause this was an air bubble, but I have bled the system.
Another problem I had was I attempted to run the boiler as a closed system to insure it wouldn't keep increasing pressure (just for a day as I was out of town) and it lost all pressure. In my mind the only thing that would cause this would be a leak somewhere in the system, could anything else cause this?
Thanks for help!