Results 1 to 8 of 8
  1. #1

    ultraviolet lights in ac ducts to dry out ducts

    We just had some work done on our two central air units.

    The tech said he noticed a musty smell coming from the registers. And, that we need to have some special ac ultraviolet lights installed in the ducts to dry them out.

    I have never heard of this!
    Last edited by Admin; 08-21-2007 at 08:16 PM.

  2. #2


    I'm not sure what the contractor was talking about. Do not install UV lights inside flex duct as it will deteriorate the inner core of flex duct. Maybe the contractor was referring to a musty smell potentially from any contaminant buildup on the coil. You can use a UV light to destroy biological contaminant growth on the coil such as mold/bacteria/virus, etc. It will not help with dust or dirt build-up.

    You can also look to install an UV Air Purifier in the return plenum which will clean the air stream as well as control any growth on the coil. There are differences in using a UV light to clean the coil vs. cleaning your airstream.

    These are the only two proper uses for UV lights and most companies only have UV lights for cleaning your coil despite their claims.

    Let me know if you have any questions.



  3. #3
    Join Date
    Mar 2005
    Feet per second to grate for UV to clean the air in the duct. You will have to have a lot of lights to do that. If it is musty have him clean the coils and pan.

  4. #4

    Can you explain please?



  5. #5
    Join Date
    Mar 2005
    UV needs contact time to kill! HVAC systems move the air to fast to have enough contact time. Only way to have more time is to have more lights.

  6. #6

    Good point, however UV also needs Intensity to achieve a high kill rate. There are two scientific principles at work - dwell time and intensity.

    Your right, most companies don't address both issue's, they only address object purification (cleaning coils) and try to apply one product to both air and object purification.

    For cleaning coils, you have all the dwell time so you don't need as much intensity.

    For cleaning the air stream, you have just a split second to purify the air, so what do you need? High Intensity. You can achieve that by more lights or you can achieve it by using aluminum reflection which is just as effective if not more and definitely more economical.

    Check out for explanations and residential products R1700GX and the R4000GX strictly for air purification.

    Regardless, txbumsteer needs to check out his coil because that's the likely source of his odor.


  7. #7
    Join Date
    May 2005
    Lubbock Texas
    TX Where do I start. There are so many misnomers out there about the use of UVGI lighting it some times sounds like the great pumpkin on Charlie Brown.
    1. The UVGI lighting by its self will remove odors by its self. Odors are VOCs
    and UVGI alone will not remove VOCs.
    2. If your duct work is wet UVGI won't dry them either. You have lost your
    vapor barrier some where on the trunk line or flex duct. Repair or replace is
    the only option.
    3. DRK you are both right and wrong on your assumption on how UVGI works
    in an air stream. Residence time is the key. In a supply duct you need with
    just UVGI at at least 55 watt an 3 uv mw watts. The bulb needs to reach
    the full length of the width of the duct. The most effective range of most
    UV bulbs is 12 inches in every direction at this wattage. So that gives you
    24 inches of effective coverage. Most of you biologics will be inactive with
    this set up. Mold spores are molecular heavier. So they take more
    residence time. So you either put two bulbs in series down the air stream
    about 18 to 20 inches apart or you depend on more air changes to achieve
    the same goals.
    4. UVGI will degrade wiring and plastic drain pans that isn't protected and
    its properties can not be measured reflecting off of sheet metal. Only
    polished aluminum or P2E
    (teflon) will reflect UVC properties. So the only effective UV energy is
    direct site from the bulb.
    5. You must make the proper air changes in a residence or facility as per
    ASHRAE 62.2 to make you UV system effective.
    6. Not all UVGI bulbs are built the same. Some purposely create ozone and the
    higher wattage bulbs can produce ozone with the loss of air flow so plan
    your system effectively

  8. #8

    Thanks for your number. I should be up in Lubbock late Sept. early Oct. I'll give you a call when I get it confirmed.

    Also, what's your name? You can email me at



Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts

Related Forums

Plumbing Talks | Contractor MagazineThe place where Electrical professionals meet.
Comfortech 365