There are some common problems that home owners encounter when performing the common task of installing a new furnace filter or air

conditioner filter. Unfortunately they don’t come with directions.

After you perform this maintenance task the first time you quickly realize that it is not difficult to do. Below are links to some articles that attempt to eliminate some of the most common obstacles often encountered when installing a new air filter for the first time.

Where is my furnace filter?

Where is my furnace filter?
Before you can change or inspect your furnace filter you have to

know where it is located. Every air conditioning and heating system should have one and they can often be difficult to find. They are usually installed in the air handler but not always.

Which way do furnace filters go?

Which way do furnace filters go?
This is an important part of changing your air conditioner filter. You don’t want install your new filter the wrong way. There are usually arrows pointing in the direction of air flow. Ignore these and you can negatively impact system performance and reduce filter life. There are some other indicators to determine which way your replacement filter should go.

How do you install a furnace filter?

How do you install a furnace filter?
Sometimes filters are difficult to remove because you can’t get your fingers into the narrow opening of the air handler to remove them. Try this easy solution to make changing your furnace filter much easier.

Question: I have a Trion Air Bear media filter installed close to my furnace in my basement.  I also have two Newfoundland dogs who shed like fiends.

I have found the expensive Trion media filters clog quickly (well before a year, more like a month) with fur. I wonder if it would make sense to install return air grille filters with cheap fibreglass filters as a sort of pre-filter to extend the life of my Trion Air Bear media filters?  It seems like this could help prevent pet fur from building up in my ducts. Do you see any problems with this?

Your Trion Air Bear filter probably has a MERV 11 rating. Furnace filters and air conditioner filters with high MERV ratings already restrict air flow so adding another filter has an even greater impact.

I typically don’t recommend using fibreglass filters because they do such a poor job and I am always cautious about using two media air filters together.

However, every filter has its use and fibreglass panel filters are great for your problem. Be very careful not to let them get too dirty because having two filters in a system can cause a number of problems. I would recommend changing them monthly at least and maybe more.

I would also recommend that you check the MERV rating of your Trion Air Bear filter. The rating should be marked on it. If the MERV rating is higher than 8 I would recommend changing it to a filter with a MERV 8 rating. These have less impact on air flow than the higher MERV filters and will still do an adequate job.

Read the articles below for more information about some of the potential problems that can be created when restriction air flow.

When to change your air conditioner filter
How often do you need to change your air conditioner filter?

One of the problems when trying to compare the different types of furnace filers available is that there is quite a bit of information to sort through. When trying to compare efficiencies, brands, MERV ratings, price, characteristics and the types of filters available, you can suffer from information overload.

The first thing to do before sorting through all of the above information is to determine what type of air filter is best suited for your specific needs. After deciding on the type of filter you want to use then it is time to compare and review the filters of that type to make your decision.

I have compiled a chart to help compare air filters most commonly used in heating and air conditioning equipment. It lists some of the pros and cons of each of the common types of filters and also lists some important details of each type.

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.