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Thread: UV systems

  1. #1
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    UV systems

    During a service call yesterday, the technician pushed for me to purchase a UV system to help keep the coil clean. I live in Southern California, so the house is fairly dry and mold is generally not a problem, but I was wondering what others think about these systems.

    -Do they inhibit bacteria/mold growth on the coil?
    -Does that help keep the coil clean, or is it more of a dust/particle issue?
    -Do they have any effect on the cleanliness of interior air?

    Thanks. I've been helping my parents buy a new system, so I've been lurking awhile, but this is my first post.

  2. #2
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    There's a whole IAQ section on this site dedicated to this particular set of questions. It's very interesting, just FYI.

    That said, the general consensus as I understand it from the IAQ section/experts, if installed, specified, and maintained correctly, UV lights can certainly keep wet coils mold-free. However, as purposed for coil cleanliness, they do not provide any where nearly the combination of exposure time and intensity required to actually treat the air itself. Whole-house filtration is a better-understood and a generally more developed technology for achieving this end.

  3. #3
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    I was told by a tech guy at one of the supply houses that the only way UV lights are effective is if the air being treated is exposed to the UV light for a minimum of 45 seconds. He said he got the info from a Lennox rep, so I have no idea what the validity to this claim is, meaning I don't know if there is any scientific research to back up this claim. Another thing to keep in mind is that most manufacturers of the UV lights recommend replacing the bulb(s) once per year. In most of my experiences, they last any where from 1-2 years, but could go longer. The bulb(s) aren't cheap either. I would just keep up on replacing your filter or installing a media filter like an aprilaire spaceguard.

  4. #4
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    big sky, the "time" factor is really only one piece of the pie. Just like hearing loss due to noise, or bacteria reduction due to high temperature (I used to work in a IV bag factory where we did terminal sterilization via huuuuuuuge "pressure cookers"), time/intensity relationship is key here. And intensity decreases very quickly with distance from the UV source.

  5. #5
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    So there is some truth to it then.

  6. #6
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    The cost savings when using a UV light on a residential air conditioner depends on how long it operates, the operating efficiency of the system and if there is a variable speed fan motor in the air handler. It would be a better idea to have a service agreement and have the contractor manually clean the coil and check out the entire air conditioning system every year. A service contract should cost you about as much as having your contractor supply and install a new UV lamp every year. Using a good filter and taping it in to prevent leaks around it is the rest of the story.

  7. #7
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    UV will keep mold from growing on the coil if it is within 6 inches. the issue is there are two sides to a coil so you will need two lights because one light will not carry to the other side. UV will do nothing to keep the coil clean. So I say keep your twice a year maintenance on your HVAC equipment and can the UV idea.

  8. #8
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    Thread Starter
    Thanks for all the info. Really helpful. I'm going to stick to the filter changes and coil cleanings.
    Is mold on a coil a particular problem in some areas or with some systems? Otherwise I don't really see how the UV would ever make sense.

  9. #9
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    If you smell a foul odor coming out of your air conditioning ductwork it may be mold growing in the condensate pan or on the coil. It is time for a clean and check. If the odor doesn't stay away for the season then you need to look up a discussion thread entitled "dirty sock".

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