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BTU needs for tankless coil

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Abro
Abro Member Posts: 37
in THE MAIN WALL
Can someone tell me how many btus are required to heat up 1GPM of water flowing through a tankless coil 100 degrees F? Where can I find that info? Thanks

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  • Robert O'Brien
    Robert O'Brien Member Posts: 3,584
    A

    BTU is the amount of energy needed to raise 1LB of water 1 degree.Water weighs 8.2 lbs/gallon.That's all the info you need to calculate

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  • Brad White_187
    Brad White_187 Member Posts: 13
    To complete the equation...

    One gallon of water weighs about 8.33 lbs. depending on density (temperature).

    1.0 GPM = 8.33 lbs. per minute x 60 minutes per hour = 499.8 lbs. per hour.

    As Robert said, a BTU is a pound of water with a change in temperature of one degree F. by definition. So 499.8 lbs. x 100 degrees F. = 49,980 BTU's per Hour (BTUH).

    Remember, that is NET heat, not the input rating of your heater. If 80% efficiency, you are looking at 62,500 BTUH input if separate gas-fired for example. In your case if an immersion coil I assume, you will still burn that much fuel but the heater coil transfer would be that net number at temperature.
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