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Annual Fuel Cost - Daniel Paul

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Daniel Paul
Daniel Paul Member Posts: 1
in THE MAIN WALL
I'm trying to figure out the cost savings on a radiant job over unit heaters in a 25,000 sqft. building. I have the formula, I just need to know what the AFUE as a decimal for both radiant and the unit heaters would be. In the Burnam helper book they give a rating of .74 for hot water, and .624 for hot air. Should I use these? Can any one help?

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  • kf_2
    kf_2 Member Posts: 118
    AFUE

    Daniel,

    AFUE is more concerned with the boiler or furnace efficiency. However, ASHRAE states that when doing a radiant heat load you are able to reduce the building volume by 15% and increase the roof R-Value by 1.5%. This means smaller BTU/hr loads thus less fuel usage. The reason for the efficiency savings between hydronic and warm air is due to the fact that 1 cubic foot of water carries far more BTU's than 1 cubic foot of air and hydronic systems are typical run at 190 degrees or less and hot is is well over 200 degrees.

    kf
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