billw wrote:Thanks Richard. I have the bladder type, actually two, one near the oil unit that was installed in 94 and the other near the coal unit installed last year. The boilers are series connected. Lowering the water temp didn't really change anything. Yesterday both first and second floor zones were gravity feeding. I did learn that the water flow is the same direction as if the circulator was on. Supply side of the zone gets warm first followed by the return. For now I'm turning both zones off and living with it cause I'm up to my ass in aligators. Hopefully Monday I'll have the chance to take a look. How do I know if the tank is bad?
I would go by the behavior. If a tank is full of water then any rise in temperature will rapidly cause the pressure to rise to 30 and start to bleed out of the pressure relief valve. As long as that is not happening I would not be concerned. Pressure only needs to be high enough to raise the water to the highest points of the system. It has nothing to do with pushing past the flow control since in a closed system the pressure is equal on both sides. The only thing I have seen that pushes water past the flow control is if the heat is high enough to cause steam, which will push past the control. If that happens though you will hear it as a rattling sound coming from the flow control. I would bite the bullet and take one of those flow valves off so you can see the seat and judge condition. Hard water over the years could make the seal bad. I don't think you can do it in place without damaging your piping, especially if it is copper.
The other thing that caught my eye in your post was the aqua stats. Normally one of them is reverse acting to prevent the circulator from pumping cold water, and the other is the limit control. Older units had three. A reverse set at about 140, a limit set at about 160 to 180 and a high limit set at about 190 to 200. Modern units have all 3 combined into one control. I just wonder if the one you have set at 140 is a reverse and not the controlling aqua stat.