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Posted by HeatPro on May 08, 2008 at 10:51:46:
In Reply to: Re: Do high efficiency boilers make sense for baseboard? posted by John Anderson on May 08, 2008 at 02:17:15:
"Furthermore at least in some regard installing an outdoor reset may net you some of the benefit of running reasonably lower temps most of the year, most contractors up here seem to say even a 15-20% gas savings yearly from just that. "
Now there lies the important answer. How do contractors explain a 20% improvement over 84% AFUE? - that is 104%. The answer lies in the problem of constantly keeping the boiler hotter than necessary due to first one zone calling for heat, then another right after it, never getting the temperature to just what is needed according to the weather. The AFUE test uses a 140F base temperature for a yearly average - make the water temperature exceed that for more than half the year and the efficiency of the heating system is less than the published AFUE.
The way to stop that waste is with the outdoor reset or a HeatMaster control.
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