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flow rate help!

worry too much about flow rate. Your outdoor reset will guarantee low return temperatures on most days.


  • Stray
    Stray Member Posts: 29

    I'm replacing my oil boiler with a Triangle Tube 110 Solo this spring. The system has baseboard fin that was installed with 1" fin and pipe.

    It's a ranch house, and has 2 zones (1,184 nsf and 795 nsf) that are simple loops. I don't know why it was piped with 1" instead of 1/2. The larger dia. pipe would have less surface area-to-volume of water.

    I'm wondering how to figure the best flow rate (and therefore spec my zone pumps accordinly). I was thinking it should be on the slow end, to get the lowest possible return temp for the condensing boiler; but I worry that the recovery rate might be real slow with the larger pipe (ie going from daytime setback to occupied temp).

    I'd appreciate any feeback, or a point in the right direction. Thanks!
  • scrook_3
    scrook_3 Member Posts: 66
    With 1\"

    just keep it under about 6-7 GPM for 1", vs less than 3-4 GPM w/ 3/4". The large pipe shouldn't be a problem, you can run higher flows if needed and move more heat, meanwhile the fin size & density on the convectors not the bare tube surface to volume ratio will define the heat transfer to the rooms.

    The lower the flow rate the less heat you'll get at the end of the loop for a given water temperature at the beginning (higher initial temperature, higher delta T); alternately if you run at higher flow rates, lower the *initial* temperature to get the same return temperature (lower initial temp, lower delta, same return temp). Either way, use outdoor reset, that'll gat you low return temps in the less than design conditions.
  • Stray
    Stray Member Posts: 29

    Thanks! Sounds like maybe I was "over thinking" it to begin with.
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