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Standby losses out the chimney

New2heatingNew2heating Posts: 1Member
Does anyone know of how I would figure out how many BTU's are going up the chimney when my boiler is on standby?  I have a Weil McClain set at 150 to 170 degrees.  Thanks!


  • heatpro02920heatpro02920 Posts: 991Member
    I normally

    call a chimney vented appliance with no outside air intake 5-10% energy loss, that is just what I notice going from natural draft to direct sidewall vent...
  • Robert O'BrienRobert O'Brien Posts: 3,107Member

    Figure out the amount of energy stored at 170 and the amount stored at 150(don't forget the differential). The difference is standby loss assuming no intervening demand. Water has a specific gravity of 1,cast iron is .09
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  • chapchap70chapchap70 Posts: 139Member
    Here's a file

    We have a Peerless 3 section with a tankless coil at our house.  I turned the boiler off and took temperature readings a couple of years ago.  I made a spreadsheet converting gallons to BTU's, etc.

    The direct and indirect numbers assume 6 to 8 degrees per hour and 1/2 to 1 degree per hour idle loss respectively.  It's been a while. 

    Have fun.
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