I had this problem many years ago. I had 3 zones and the main one would not shut down. I didn't have zone valves, I had separate circulators and check valves. I finally confirmed it was the check valve that was stuck open. I took apart the one that was sticking and found a piece of black rubber stuck holding the check valve open. Problem fixed, or so I thought.
A week later it did it again. I took the valve apart and found another piece of black rubber. Not knowing a whole lot about plumbing and heating I tolded my burner guy about what I found and he told me the expansion tank was coming apart inside. I changed the expansion tank and problem was solve for good.
|