The water level for my boiler seems to go above the labeled height. We now have a sporadic water leak that is not showing itself. Could it be that the excess water in the boiler is causing this ovrflow condition?
Two common causes of overfilled boilers are a defective auto fill valve (if equipped) and the tankless coil. You can test the auto fill valve by shutting off the supply line to the boiler. If the overfill condition ceases the auto fill is the culprit. If you have a tankless water heater (a coil inside the boiler that makes your hot water) it may be leaking. The leak allows uncontrolled domestic water to enter the boiler causing the overfill condition.