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Posted by HeatPro on January 13, 2005 at 08:26:56:
In Reply to: Re: Boiler Comparison posted by Eric on January 13, 2005 at 07:37:31:
The margin of 1.15 is built into the IBR ratings. If you compare the doe heating capacity coming out of the boiler to the IBR rating you will see that 15% is deducted from the output to account for losses from pipe and extra to reheat from setback. As heat losses are done using a worst-case scenario of the average coldest weather data at night when no sun is heating the area and people are not using appliances, heat estimations have a margin built-in of about 20% to start with. Adding more make sthe unit oversized and cycles shorter. A good heat estimate and using the IBR rating will usually wind up with the boiler running about 50 minutes out of an hour in the coldest weather.
I have a gas boiler, so I tweak my input down to let the thermometer drop back to 66F in the rare coldest weather and warm myself with a 1500 Watt electric radiant heater where I sit; it saves much and I enjoy the radiant warmth. That's not easy for everyone to do, so just using the IBR rating for the heat estimate is enough to not let the thermometer drop.
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