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Posted by HeatPro on September 02, 2004 at 09:18:33:
In Reply to: efficiency steam vs hot water posted by mark d. on September 02, 2004 at 07:29:12:
Steam pipes must reach 215F each and every heating cycle, whether mild or cold weather. The outside surface of steam pipes and their weight is heavier than hot water pipes, so there is much more waste from steam systems than hot water systems. The requirement that boilers must heat water over the boiling point makes condensing the combustion gases in the heat exchange surfaces of the boiler passages close to impossible, so steam boilers are less efficient than condensing hot water boilers. Steam boilers would be less than 87% efficient; condensing hot water boilers over 94% efficient.
The ability to not heat the water and pipes in closed zones helps make even less loss for hot water systems. Not heating is more efficient than heating unneeded areas.