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Moisture in heat exchanger

Redoak1963 Member Posts: 1
I notice drops of water in the inspection ports on my forced air oil furnace. What could be causing this? The basement is unheated and it has a outside cement block chimney.


  • unclejohn
    unclejohn Member Posts: 1,833
    Maybe just condensation. 
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 6,032
    edited February 2021
    Describe "inspection port"

    I am picturing the openings in the heat exchanger (HX) where you inspect for soot buildup and run a brush thru when you vacuum clean the HX. If the condensation is there, the firing rate may be too low for the Return air temperature or basement (furnace room) ambient temperature. Is the proper nozzle size and pump pressure installed, or has someone derated it to increase efficiency? Condensation of flue gasses on an oil furnace should not even start to happen until halfway up the chimney in an underfired appliance. if it is starting inside the HX you are way underfired.

    Do you have a properly adjusted barometric draft control damper?

    Respectfully submitted,
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics