Posted by Harold Kestenholz - Hydronic Network on February 04, 2000 at 11:21:51:
In Reply to: Only Air Vent Required to Stop Banging? posted by George on February 04, 2000 at 01:05:16:
Air in the system won't make your pipes jump around unless there is so much that water won't flow through some zones; you'll get some thunks and water flow noises. You can tell if water is flowing through by the warm or hot water in the pipes.
This boiler has small tubes with fire playing on them. When one or a few zones are open, there may not be enough water flowing through the boiler to prevent the water inside the tubes from boiling and making the steam collapse inside the cooler tubing, so the boiler piping will jump around. There is a bulletin from the manufacturer showing how to install a bypass pipe from supply to return to make sure enough water flows through the boiler to prevent steam. Not all installers are "up" to this requirement for small-tube boilers, so they sometimes miss installing the minimum flow bypass.
You can find out more about hot water design in the free lessons at http://www.hydronic.net