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Powder puff test for heat exchanger?

My boss recently gave us techs a little “test kit” for checking heat exchanger integrity. It consists of a little rubber bulb filled with a very fine powder and an attached rubber tube. The idea is to have the furnace set to off with just the fan running. You squeeze a little puff of powder into each chamber entrance and if the powder blows back he wants the furnace condemned. I haven’t found any info on using this powder test anywhere online and nobody I know has used it for checking exchangers.
Any thoughts on this “test”?
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Comments

  • Jamie HallJamie Hall Posts: 10,407Member
    Never ran into that, but I can see how it would work: you are looking to the fan to pressurize one side of the heat exchanger, and if there is a leak that will blow out the other, where you put the powder. Not sure how sensitive it would be, though.
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • STEVEusaPASTEVEusaPA Posts: 2,866Member
    What if with the unit off you're getting a little down draft or back draft? Do you block the flue and combustion air intake as well?

    Doesn't seem conclusive enough to condemn a furnace, seems more like an easy way to talk people into getting a new furnace.

    But I guess if it does blow back you should investigate further to look for a visual clue.

    I'd trust my analyzer first, then smoke candle. If any of those threw a clue, I'd do a visual.
    steve
  • SuperTechSuperTech Posts: 938Member
    I'm with Steve on this 100%. Sounds like an attempt to scam customers.

    I hope your boss provides you with a digital combustion analyzer so you can test the safety the equipment the proper way.

    Digital analysis or smoke pen
  • GrallertGrallert Posts: 320Member
    I've used my combustion analyzer to test for faults in heat exchangers. It seems that the O2 sensor is accurate enough to pick up any drop in oxygen levels. Also CO numbers will climb but not as clearly as the O2 level. This will prompt me to investigate further.
  • SuperTechSuperTech Posts: 938Member
    There's nothing wrong with pulling out the blower assembly and visually inspecting the heat exchanger. A digital inspection camera makes it easier to find flaws in the heat exchanger.

    Don't ever condemn a heat exchanger unless you are positive it's shot. I've been to several houses this year that other "techs" have condemned units based on appearance of the flame or other ridiculous reasons in an attempt to sell new equipment. One idiot from another company was fired after I proved that the furnace he condemned was fine.
  • BlueFrostLLCBlueFrostLLC Posts: 3Member
    Yeah, I’m not feeling the powder alone process. We used to have classes with Ellis Prach for inspecting exchangers so using a mirror, camera, even water spray in my preferred way to the powder. It seems too inconsistent or inconclusive
  • Alan WelchAlan Welch Posts: 140Member
    If there is a heating register or humidifier mounted on the supply plenum that can be easily removed, I will to see if any light visible when the burner runs. I have found several that way.
  • ratioratio Posts: 1,965Member

    If there is a heating register or humidifier mounted on the supply plenum that can be easily removed, I will to see if any light visible when the burner runs. I have found several that way.

    Now that's downright scary!

    The last HX I condemned I never did find a hole, but the pressure switch would open after the HX was warm. I suppose it could have been some kind of blockage.

  • HVACNUTHVACNUT Posts: 2,135Member
    The analyzer is the only way to go.
    For an oil furnace I have a hand held Dwyer draft gauge. Over fire test with fan off/on. It hasn't failed me yet. Analyzer for proof.
  • GBartGBart Posts: 753Member
    edited January 11
    SCAM

    I had one years ago, boss sent me to check out a new customer who had another company tell her the heat x was shot, I could find nothing so I asked her what he did, she said he did a Halide Test............really? I said, just how did he do this.

    She said he had a sprayer bottle with some crystals in it and needed to get some water, he filled to a level and fired the unit up, with her watching he sprayed this through the inspection door and said "see, the fire changes color, that means you need a new furnace, the heat x is shot and very unsafe"

    I told her that was a scam and to call the state.
  • JUGHNEJUGHNE Posts: 5,653Member


    Two of these were changed just for upgrade.
    Installed in school building in 1969..counterflow.
    Apparently had holes for a long time.
    Outdoor air connection to return duct and leaky building kept kids awake.
  • GBartGBart Posts: 753Member
    well then whoever was doing service hasn't checked them
  • Alan WelchAlan Welch Posts: 140Member
    Went on a no heat call when I first started over 30 years ago. The hole round top of Armstrong heat exchanger dropped into the firebox because of humidifier mounted on supply plenum.. Asked owner if she had noticed any smells, nope.
  • Jamie HallJamie Hall Posts: 10,407Member
    I still think that as a nogo text it's not really a scam -- but it certainly isn't going to be definitive. It will suggest that there is a potential leak -- which then absolutely has to be checked out by other means.
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • BlueFrostLLCBlueFrostLLC Posts: 3Member
    I really appreciate all of these comments, I had my doubts and could find NOTHING online about using powder to test heat x condition. You all have confirmed my concerns
  • JUGHNEJUGHNE Posts: 5,653Member
    That school administration was saving money by having the janitor fix things after they broke. :/
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