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    Residual heat from boiler and radiator piping (3 Posts)

  • Robert_H Robert_H @ 9:39 AM
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    Residual heat from boiler and radiator piping

    With the new system I was planning to put an old cast rad in the basement to supplement the heat. But in sizing it I was wondering how much the boiler and piping are going to contribute to the warmth of the basement. This might be a stupid question but, Could I leave the radiator out and the system would respond to the heat loss through the PEX.  As we have always heated with wood in this house I have no feel for how much residual heat a boiler/piping put out. The basement is just for storage and I have a workshop down there.

    House 42k
    1st floor 19k
    2nd floor 9.7k
    Basement 13k

    The first floor radiators are all piped through the basement (home run) with 1/2inch fostapex.  About 220 ft total.
    The boiler is a Vitodens 200 B2HA-19 running continuous on ODR. Radiators are on TRVs.

    Is it worth considering or is it  negligible?

    I assume it could be calculated but am not sure where to start.

  • Jamie Hall Jamie Hall @ 11:12 AM
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    Yes, it can be calculated... but...

    It's not that hard to calculate, actually.  Half inch pipe is more or less 1/8 square feet of radiation equivalent per foot of pipe.  Give or take.  So your 220 feet would be somewhere around say 25 square feet of radiation, equivalent.  Perhaps, at a reasonable home run temp, around 2500 BTU lost.

    Which is trivial.

    So is the heat lost to the area from a modern boiler -- they are designed, no surprise, to put as much of the heat as possible into the circulating water!

    So my suggestion would be to not worry about it and put a decent sized radiator in there with its own TRV.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Robert_H Robert_H @ 1:34 PM
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    Thanks Jamie, that makes good sense.
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