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Flue condensation - 3 pass boilers

Rudy Member Posts: 482
I am considering installing a Buderus G115-34 with indirect, but have been warned about condensation issues when venting into a typical exterior tile lined chimney (8x8). I am also considering using the Logamatic R2107 with outdoor reset. I understand that this will help reduce internal boiler condensation by controlling (preserving) boiler core temp, but will not necessarly address flue condensation (i.e., maintaining appropriate stack temp).

Does anyone have practical experience with controlling the stack temp of the Buderus G115? How likely is flue condensation and is it worth the investment to just install a flue liner from day 1? Buderus recommends 5" flue for the G115, but would installing a more common 6" diameter also work?


  • Robert O'Connor_7
    Robert O'Connor_7 Member Posts: 688
    Chimney Liner

    I would install the liner. Check both of the manufacturers installation instructions first!! Very important!! Your gonna need to know the height, type of liner, and btu. I would always suggest a liner for a forced hydronic in a cold chimney. Gotta have just the right size.. Good luck BOC
  • Mike Kraft_2
    Mike Kraft_2 Member Posts: 398

    Absolutely have a liner installed.Stainless steel for oil fired.Sizing the liner is also just as important as the sizing of your boiler.The 115 has a baffle system which is adjustable to accommadate your stack temps.The Logamatic 2107 is a very nice control.I have several out there running for years with no complaints.

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