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Posted by HeatPro on January 13, 2005 at 12:08:19:
In Reply to: sizing boiler posted by Daniel on January 13, 2005 at 11:05:52:
All that has nothing to do with it. As your existing system is a gravity-fed boiler, then installing a new boiler with large passages, like most Americna-made boilers would work the same. A gravity system would have no zones because shutting off a section of the pathways for water to flow would stop the flow and take a long time to reestablish the flow. If you meant you have several circuits, then they would be left open if they remain gravity flow.
If you want four zones, then you would have four circulators or zone valves and a circulator that would establish flow mechanically.
In any of those situations, you would need a boiler that can provide the heat estimate of the home. If there are cast-iron radiators, make the boiler 40% more output than the heat estimate to make up for heating the metal and all that water.