Question: I am having problems with allergies in Florida. As I am replacing our A/C unit I am looking for a really good filter. The Trane cleaneffect unit looks promising, but would it be good enough. Is it worth the extra cost to get a UV filter. Any recommendations would be appreciated. The installers have all been recommending not to use a uv type and just go with the Trane.

In my opinion, it depends on how bad your allergies are. If your allergies are very bad and cost is not a factor, I would say the extra protection a duct mounted UV air cleaner provides is not a bad addition to enhance a media air filter. UV air cleaners  kill bacteria, mold spores and other organic contaminants. That is something  a media air filter can’t do.

It’s also important to point out that a uv air cleaner is only suitable for enhancing the filtration of a traditional air filter and should never be used as the only method of air treatment. UV air cleaners do not actually filter the air, they only purify it by killing organic compounds. You still have to filter out those contaminants with mechanical filtration.

The Trane CleanEffects air filter is very efficient and Trane rates it even  better than a HEPA filter. That’s very impressive. I do have some concerns  about the Trane CleanEffects filter. You can read my thoughts in this post Trane CleanEffects Review.

That article is only based on what I have read about the filter because I  don’t have any first hand experience with it. I am hoping to get some comments in that post from people who are using it.

Question: Do you think there is  any problem with ultraviolet furnace filters as far  as it depleting the inside of the Duct liner or plastic or rubber that the ultraviolet rays bounce off.

It depends on the type of plastic your condensate pan is made of.  Some of the newer drain pans are UV resistant but you would have to check with the manufacturer to know for sure.  UV also causes rubber to deteriorate.

There are a few of things you can do to avoid this potential problem.

- Install the UV air cleaner in the return duct before the ac unit.  This way the light doesn’t contact the drain pan or any other plastic parts.

- Mount it in the supply duct far enough away so that it doesn’t contact the drain pan or any other plastic parts.

- Place a shade of some sort above the condensate pan to prevent the UV rays from contacting the drain pan.  You have to be not to do anything that can potentially affect air flow.

What I recommend is that you install the uv air cleaner in the supply air duct.  This will treat the air before it enters your living space and destroy most mold spores, bacteria, viruses and other pathogens.

I often read that UV lights should also shine on the evaporator coil to destroy any mold that may grow there.  I have worked on thousands of air conditioners and have seen very few with mold growing on an evaporator coil.  I have seen many dirty evaporator coils but that doesn’t mean there is mold.

I have seen condensate pans, drain lines and p-traps with some nasty looking things growing in them that I handle carefully.  The reason things grow in these places is because a lot of contaminants from the air collects there.  The evaporator coil is wet from condensation most of the time and as air passes through the evaporator coil, contaminants collect on the coil and many of these contaminants are washed away with the moisture on the coil as it drains off.  So the coil actually stays fairly clean for a long time when using efficient furnace filters and a lot of the contaminants collect in the drain pan, drain line and p-trap.  You can treat these components with a mixture of bleach and water, about 10 parts water to 1 part bleach.

If, for some reason you are having problems with mold on the evaporator coil contact your service technician and have him or her clean the coil with one of the many chemicals available.  There are environmentally friendlier cleaners available also.

Regarding the duct liner, I don’t think UV light would have any effect on it.

Update Dec31/08

I submited this question (Do uv lamps damage plastic condensate pans and rubber?) to a popular UV air cleaner manufacturer and this is the reply that I received.

Question: I have a UV air cleaner in my home.  What MERV rating air filter do I need to use?  Would it be beneficial to use a MERV 11 filter or would a MERV 8 work?  I change my filter every month when it’s running but I will go for 3 months.  I have changed the filter at different times and it seemed (by the naked eye) clean.  Should I let it go longer or still go on the same maintenance cycles?

A UV air cleaner doesn’t eliminate the need for efficient air conditioner filters.  The UV air cleaner will help to kill mold spores, bacteria and viruses but they don’t actually filter the air, they only purify it.  You still require an efficient air filter to remove dust particles from the air.

A MERV 8 filter is adequate for most homes unless you want to maintain the best air quality possible.  A MERV 11 filter is very efficient and will do a good job.

How often should you change your filter

It is best to follow manufacturer recommendations for filter change frequency.  They know their products and can better guide you in this area.

Personally, I think changing furnace filters and air conditioner filters every month is more often than necessary.  I usually change filters every 3 months in commercial buildings.  If every 3 months is good enough for these applications, where there is more dust, then it should be fine for residential applications.

One thing to consider is that filters used in commercial applications usually aren’t as efficient as the ones used in residential applications so they don’t become dirty as quickly.

If you can tell by looking at your furnace filter or air conditioner filter that it is not getting dirty then it probably doesn’t need to be changed for a while.

Other articles about how often to change air filters

When To Change Your Air Conditioner Filter

Every house is different and there are many factors that determine how often your heating and air conditioning filters should be replaced. If you wait too long operating efficiency begins to decline, as efficiency drops operating costs increase. Changing your air filter more often than necessary is like throwing money away.