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Black around supply registers

Jamie_6
Jamie_6 Member Posts: 710
I was just in a home with an oil fired hot air furnace. Around all of the supply registers I found a black dirt. I checked the supply duct work for CO and found none. What would cause this dirt?

Thanks,
Jamie

Comments

  • Mark A. Custis
    Mark A. Custis Member Posts: 247
    Mold Spores

    And they test in the lab just like pertro chemical. Could have and Oil burner belching and being picked up by a leaky return air system.

    Mark

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  • john wood
    john wood Member Posts: 44
    CANDLES!!

    Seen it plenty of times. They make a ton of soot particles too small to see, but stick on carpet etc. around registers and baseboard convectors.
  • Mark A. Custis
    Mark A. Custis Member Posts: 247
    John is correct about

    candles. See what happens when you get my age and are only using one or two sences to trouble shoot? CRS, if you don't know you don't have it.

    Thanks John,

    Mark

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  • Dale_3
    Dale_3 Member Posts: 58
    Dirt around air registers

    It may have nothing to do with the oil burner. Depending on the air velocity out of the registers you can cause a charging effect of the air. With the ceiling being the opposite charge the dirt particles in the air attract to the cieling. It could just be dirt in the house collecting there. Sorry if I misread your post but I see this a lot in commercial building where the air velocity out of the registers tends to be at a point high enough to cause this more often than in residential situations. Dale
  • Steve Levine
    Steve Levine Member Posts: 106
    My belief,

    is that when air comes out of a register or diffuser at a significant velocity, it aspirates air from the space into the stream. This pulls particles along with the air, and they can deposit around the outlets.
  • Mark A. Custis
    Mark A. Custis Member Posts: 247
    I don't know if

    it matters how the stuff got there as much as what is it.

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  • Steve Levine
    Steve Levine Member Posts: 106
    Yes,

    but the point is that it usually is not coming through the ducts.
    Steve
  • Mark Hunt
    Mark Hunt Member Posts: 4,909
    I bet

    that if you looked around you would find that the return duct work is not sealed and air is also getting in AFTER the air filter. The return duct is under negative pressure and it doesn't care where the air comes from.

    The "standard" air filters installed on many FHA units will not stop dust. If you want to prove it to a customer, have them poor some table salt onto the filter and watch it fall right through. Now if it can't stop a grain of salt, what would make any one think it will stop dust or any other small particle?

    It is a common practice to use joist bays and wall cavities as return duct. Plumbers and electricians drill holes from the bottom of the house to the top. If they happen to drill through a wall cavity or joist bay that is being used for return air, the air will be drawn from the space that the hole(s) lead to. Could be the attic or the basement or any where.

    I have yet to see an air tight door for a blower compartment and most of the air filter racks allow huge amounts of air to by-pass the filter all together.

    As long as you have determined that we are not looking at a comprimised HX, the only thing you can tell the customer is to have the ducts cleaned and sealed and to get a good filter. We prefer the high density media type.

    Hope this helps!

    Mark H

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  • Al D'Ambola
    Al D'Ambola Member Posts: 18
    A venturi

    effect is taking place when the air hits the backside of the grille it creates a back pressure between the boot where the grille is located on and the floor or wall.

    If you remove the grille you will see a space between the floor board and the grille, if you seal this with caulk you will prevent the venturi effect.I have seen this in hundreds of homes across the country. Once sealed I have never seen or heard from other contractors that said the problem came back.
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