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Looking for small/cheap wall mounted boiler that has cascading vent

baltik Member Posts: 21
I have a very small heat load and was looking at the rinnai m-series as well as IBC HC-13-50. One feature that would be really nice to have is a cascading venting option so I can tie into my existing 2” exhaust line that’s setup for my navien npe. Any ideas?


  • GGross
    GGross Member Posts: 696
    You are almost definitely not going to be able to common vent 2 boilers in a 2" flue. I would be shocked if any condensing manufacturers approved common venting their equipment with other brands of equipment at all, most require that common vents only contain identical pieces of equipment.
  • baltik
    baltik Member Posts: 21
    Got it, would upsizing to 3” change that?
  • GroundUp
    GroundUp Member Posts: 1,649
    I think you can common vent Navien appliances together (at least you can with multiple boilers), but certainly not with 2" pipe. Check into Navien's literature and see what you can find there
    EBEBRATT-Ed Member Posts: 13,783
    Best to keep them separate to avoid warranty and other issues.
  • EzzyT
    EzzyT Member Posts: 1,269
    Common venting can only be done as per manufacturers specifications with same model and sized equipment. You are not allowed to common vent a boiler and tankless water heater.