Ultraviolet Irradiation Light in A/C Unit? Good Science?

jerzeegirlApril 7, 2006

I am so new to the concept of central AC (this is my first house with central AC) that I wonder if any of you can help me.

I recently had my AC serviced and the AC guy recommended installing a Ultraviolet Irradiation light in the Air Handler to kill any mold or other bad things that may grow on the the coils.

At first I thought he was blowing smoke and was never going to call him back. But after doing a little research on thse UV lights I notice that some think they are good and some think they are useless.

I am just trying to figure out if it's good science and I just don't know enough about the process to make this judgement. I was told it's the same process they use to irradiate food.

I know that there are a bunch of scientists here so I thought maybe someone can shed some light and tell me at minimum if this process makes sense. The UV Light gets installed in the Air Handler and the light itself kills molds and spores.

I already posted this in Heating and AC Forum but didn't feel that the responses were based on science; they were mostly anecdotal. Any help on this subject would be great!

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I have no experience with A/C (don't ya love posts that start out like that?) but I would suggest posting in the Building a Home forum. A poster there, rabadger, designs HVAC systems for a living and is very knowledgeable and helpful.

And FWIW, we have a u/v light on our water system that *I think* is designed to rid the water of e coli and mold, but I am not exactly fluent in the details of the system, so don't take my word for it.


    Bookmark   April 7, 2006 at 2:37PM
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We have a UV filter on our air handler--for both A/C and Heat. According to my BIL (PhD/MD from Stanford--specialized in microbiology)it helps--particularly with molds, which 3/4 of my family are allergic to. (Yeah, I know that's a dangling participle, AND a I split an infinitive.)

I did a search--trying to find you some specific study--and have linked a "google answeres" thread that contains lots of links to studies.

More anecdotal evidence:
We have a UV filter AND a specialized air-filter--and have noticed a significant decrease in allergy symptoms!


Here is a link that might be useful: UV filter thread

    Bookmark   April 7, 2006 at 6:34PM
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I have a Second Wind UV air purifier. This website happens to be the one I got mine from, but it has a couple of links, one to test results of UV air purifiers. Lots of data to support that they work, provided you use the right ones.

Here is a link that might be useful: UV Air Purifier article

    Bookmark   April 7, 2006 at 7:59PM
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Thanks all. I am inclined to get the system but wanted to make sure the science makes sense. It's $750 so not cheap.

    Bookmark   April 8, 2006 at 11:43AM
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But if your doctor writes a script for it to help with allergies, is it deductible as a medical expense?

    Bookmark   April 8, 2006 at 12:27PM
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Hi jerzeegirl, I can speak to this with confidence. When I first moved into my home, I kept coming down with bronchial afflictions, one of which moved into pneumonia. I kept tasting ''smoke'' in my lungs and couldn't figure it out. I heard about UV lights for the heating/ac system and decided to look into it. My husband asked the guy he bought our lights from if he'd had any personal experience with these, and he said YES. Then he told the story about his house always smelling like ''smoke''. When I heard this I started to cry, because I knew that someone else had the same experience, and my husband finally got it. We had them installed, and I haven't been sick from mold since. In my opinion, if you're allergic to mold, you will notice a difference within two weeks. It took about that long to kill everything, and I haven't tasted smoke in my lungs since. Being sick was taking huge chunks out of my life. UV lights are absolutely worth every penny you spend, if mold is a problem for you.

    Bookmark   April 8, 2006 at 1:40PM
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Jerzeegirl: one more thing. I don't know if you've kept up on the thread in HVAC, but since I don't know terminology that well I'd suggest you make sure that the UV light will be effective not only during the cooling season but also during the heating season when the furnace is running (if you have one). Indoor air pollution is just as bad if not worse in the wintertime when you don't get fresh air from open windows.

    Bookmark   April 8, 2006 at 2:53PM
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Remember the bulbs have a specific life and need to be changed often. They are horrifically expensive.

Serious fish enthusiasts such as those who keep koi and huge fish tanks use them to kill bacteria.

    Bookmark   April 8, 2006 at 4:25PM
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Often is subjective (recommended is once a year, which may be a tad overkill). Even if it's not, one bulb costs less than a trip to the doctor's office. We have four bulbs on our unit. Would I rather be chronically sick? Uh....NO. Between time lost, trips to the Dr.'s office and meds, the lights pay for themselves if you have allergies to mold. (Not to mention generally feeling cr*ppy all the time.) The cost of bulbs is far, far less than I pay for health insurance. If someone doesn't need this, health and good news for them. No one's health is worth risking if you can afford to do this.

I had two very well cared for canaries I kept in my home office who dropped dead one day. (One was five years old, the other 10 years.) It totally freaked me out. I remember now (hindsight being 20/20) they were wheezy and it was the height of a long hot summer. I worried about radon, and had two tests done that turned out inconclusive. Mold can be debilitating. I've lost a huge chunk of my life/time living in this house (1996 - 2002) that I had come to believe was a ''sick'' house. My worst nightmare is not being able to breathe...

    Bookmark   April 8, 2006 at 5:46PM
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Correction: We only have two bulbs on our H/AC unit (not four as I posted above). I was confused, since we keep extras on hand, and the last time we bought these we bought 4. They turned out to be under $50 each. Horrifically expensive? Not to me...

    Bookmark   April 8, 2006 at 6:59PM
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Thank you all! Claire, what a testimonial for UV lights! We have a new AC guy coming on Thursday to give us a second opinion. The first guy may be right but he really ticked me off. I actually think he ripped us off. We called him to service the AC, charged my $150 ($50 of this was for a pound of Freon) and didn't even clean the unit! The second place I called charges $95 and they actually clean the AC and Air Handler and whatever else is done during a service call.

Anywy, I really appreciate your input; we are now very very inclined to have the unit installed. Thanks!

Pecan: I'll get DH to check with his allergist that's a good idea.

Hampton: Yikes a $50 light bulb! Oh well. The air filter I just bought cost $15. The water filter for the fridge costs $35 every six months. I guess I'll just have to add it to the list.

catluvr: I don't have a furnace but a heat pump which is outdoors so I don't think they can install the light our there!

    Bookmark   April 9, 2006 at 8:53PM
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At our house the light is installed in the airhandler. Now, granted, we use the same airhandler for AC and Heat--but you probably do as well. That is where our UV light AND our SERIOUS air filter is, as well. I don't remember who makes our UV filter--and the bulb in the furnace room is burned out--but our air filter is made by Honeywell--it's called a Media Filter.

I can tell you that the media filter has made a HUGE difference in the surface dust I see...gotta believe it's helping in general. They aren't cheap--but with our allergies--it's made us happier people.


Here is a link that might be useful: Honeywell Media Filter

    Bookmark   April 9, 2006 at 9:57PM
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msgee: I am a bit confused now. We have an air handler in the attic and a heat pump-a/c unit (outside), but our filter is located in the ceiling in the center hallway of the house (not on the unit). I bought the highest quality 3M filter they had ($15 and it lasts three months), but I am not aware of any filters on the air handler itself. Or maybe there is one but I don't know about it! I would buy the media filter in a second if there was a place to install it. Our air handler is in the attic and I have never actually seen it. My DH has and he says its in a location that has no floor around it so it would be difficult for him to clean regularly (in other words, we need a professional). Or perhaps we should install a floor up there!

    Bookmark   April 10, 2006 at 9:45AM
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I'm not certain--but I THINK you've been replacing the filter on your main cold air return, NOT the filter for your heat pump. Is it a big grid/vent in the ceiling, that leads to a duct? If so--that is DEFINITELY a cold air return--NOT the main filter for your airhandler. I wish I could take a picture of my cold air return--to show you--but the digital camera is at college with its owner.

I've included a link to a page that shows the anatomy of a heat-pump airhandler. You will see that the filter is at the bottom of the air handler. This may not be the same model as YOUR air handler--but I think they are all pretty similar in anatomy. When you purchased you house did you receive owner's manuals for your heat pump and airhandler? You should have. They should show a schematic (hope that's the correct word) for your unit--including the location of the filter.

We have our furnace serviced every fall and our AC every spring. We are on a service contract. One of the benefits of being under a service contract is that if something goes horribly wrong (why does the AC always break down in JULY and the furnace in JANUARY?)we get moved ahead of NON-contract people on the servicing list.
To my mind it's worth it.

Good luck!


Here is a link that might be useful: anataomy of a heat-pump airhandler

    Bookmark   April 10, 2006 at 11:50AM
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Ours is a Frigidaire and I didn't even KNOW there was a filter in it. But regardless that's why we called the people who installed the unit 3 years ago - to service the unit. I am pretty sure he didn't replace any filter. All he told me was that the air handler had to be cleaned and it was going to cost an additional $150, but if I had the UV light put in, the whole thing was going to cost $750 (including the cleaning). I think I am going to give them a call to find out why they charged me and didn't clean the unit.

    Bookmark   April 10, 2006 at 1:01PM
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OK--I went an put a lightbulb in the furnace room light and took a good look. Our airhandler is part of our furnace. That has a filter. The UV light and additional MEDIA filter are in the duct work that handles all the air to the house. Even when the furnace isn't in use--it's blower moves the air through the ducts.

I found my manual online by googling the make and model of my furnace. You know the make of your air-handler--Frigidaire--if you know the model number as well you may be able to get the manual online. (I found the manual for my furnace online.)

I may be completely mistaken about the filter for you Heat Pump. Perhaps you have been changing the correct filter. But if you haven't (through no fault of your own!) then I'm certain that the airhandler needs a good cleaning. You may find your heating and cooling bills are reduced once it IS cleaned!

Good luck--and keep us posted!


    Bookmark   April 10, 2006 at 1:37PM
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A thought occurred...
I think you should re-post over on heating and AC. Ask if the airhandler for your make and model of heat pump has a filter IN the air handler. Describe what you've been changing THINKING it was the correct filter for the past three years.

I would consider titling my thread:

"Have I changed the WRONG FILTER for three years?!?" Or some such. (Dramamtic posts tend to get attention, no?)


    Bookmark   April 10, 2006 at 1:43PM
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Well, I called the A/C guy, didn't say who I was and asked him what a maintenance visit involved. He said it involved checking the units, making sure the drain lines are clear and up to 2 pounds of Freon. But it did not include cleaning the coils. So I told him that his company just did a maintenance call on my ac system and charged me for the Freon ($50). He very reluctantly agreed to give me a refund (his sounded quite ticked off). Anyway, at least now I know he's a crook and I am quite glad we did not get the UV light from his company.

In the meantime, the new AC company is coming on Thursday so I will ask them at that time whether there is a filter in the Air Handler. I couldn't find the service manual on line but hopefully I have one at home (although I don't remember ever getting one).

    Bookmark   April 10, 2006 at 3:10PM
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