Posted by Harold Kestenholz - Hydronic Network on May 21, 2001 at 19:05:03:
In Reply to: New boiler posted by EllFol on May 21, 2001 at 14:44:47:
Gas boilers before 1980 were generally below 60% AFUE due to open draft hoods without dampers. They threw a lot of heat away when the burners were off and the boiler was just sitting throwing heat away up the chimney. Your boiler is about 30% oversized so it sits there longer than one sized to take care of the heat given off by the baseboards. Installing dampers on them to keep the heat in the boiler raised efficiency about 10%.
The new controlled combustion boilers with induced draft fans get AFUE efficiencies over 80%, so there is a significant savings in installing a new boiler.
265 feet of baseboard is about 160,000 btu output (265 x 600 btuh/ft = 159,000) maximum, so you would need a 200,000 btuh modern boiler to do the job. A Weil CGi-7 is a baseline good-efficiency model.
http://www.weil-mclain.com/netdocs/ratingscgi.htm