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Build-up in condensate collector box

Greg_4 Member Posts: 32
in condensate collector box of a 90+ furnace. Had a no heat call in a Bryant MAV-350 90+ furnace. Diagnostic Codes indicated combustion air problem. Diagnosis with multi meter indicated pressure switch would not 'make'.
Could only get unit to fire with burner cover plate removed. Determined the combustion air piping and rooftop concentric clear of obstructions. Later, checked all lines to/from pressure switch, to discover the line outlet at collector box had plugged. Possibly from slime or some organic growth. Water should not contain lime, as this is condensate water, not below earth source so it is likely not a calcium build up.

Coincidentally, Bryant rep was in this AM and mentioned this plugging as a sometimes problem in older 90+ units. A more experienced staff member said he'd been to same home last year and the tube leading to pressure switch at collector box was plugged then.

How could one prevent these blockage in the future? Is there a chemical or other method to help prevent/ clear growth which must be causing the blockages?

Thanks - Greg


  • J.C.A.
    J.C.A. Member Posts: 349
    Proving switches/condensate

    The water can come from humidity in the air . The addition of heat gives the "goo/festering stuff" the ability to grow .
    I ran into these same problems in the early fall, and trust me , the brand doesn't make a whole lot of difference .

    Maybe an exercise cycle ,just run the fan once in a while, like they do to heat circulators on some control systems ? How would they be able to
    determine how often ? Chris
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
    Condensate Organics

    Certain life seems to thrive in condensate.

    Am not at all surprised that this is showing up in older units--just like it shows up in A/C condensate.

    I believe both are biofilms--nothing "new" about this except the recent classification.

    Regular applications of bleach seem to work with A/C condensate but such can't be counted on to occur.

    The nasty thing about biofilms is that they exist in conditions that commonly sterilize.
  • Greg_4
    Greg_4 Member Posts: 32
    Bryant rep suggested-

    occasional bleach application. Kind of a chore to get to this particular tube outlet, as the inducer blower must be removed to get to the port, or if I had my younger daughter's small hands...

    Thanks - and thanks to all the Wallies for input, advice and suggestions over the last 4 years I've visited this site.

This discussion has been closed.