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Posted by HeatPro on March 28, 2008 at 17:21:24:
In Reply to: Re: Boiler Upgrade posted by Doug B on March 28, 2008 at 15:16:06:
: If i'm reading the diagram right, the IFWH is installed with a zone valve, using the main circulator pump for suction, as would be for a typical second zone.
++ both new circulator circuits or zone valves are possible arrangements. An IFWH is a second zone.
the aquastat on the IFWH continues to fire the boiler to keep the storage tank at temperature. with such a small amount of water circulating in this arrangement, wouldn't this short cycle the boiler?
++ No, the boiler water is hotter than the tank water and 15 minute or so boiler run times are usual. It is not a matter of a little hot water going in, then sitting for a while to transfer heat. A long demand might require the boiler to fire continuously, like 170F boiler water to make 70 gallons of hot water output. The boiler doesn't fire until the tank thermostat calls for heat, just as upstairs heat demand.
: A condensing boiler would require me to sleeve the existing flue, which i also didn't want to do because its an added expense.
++ Thus there is probably less than 5% gain by getting a new boiler as a non-condensing boiler keeps it in the 85% AFUE range.
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