An air filter change indicator can potentially save you hundreds of dollars on replacement air filters and can even lead to reduced operating costs for your air conditioner, heat pump or furnace.

How is this possible?

• Change your furnace filter or air conditioner filter too often and it’s like throwing money away.
• Wait too long between filter changes and equipment operating efficiency begins to decline.

How often should an air filter be changed?

Manufacturers often differ in their recommended filter change frequency. Some say every month, some say every other month and others recommend every three months and that’s only for 1 and 2 inch filters. If you use 4, 5 or 6 inch pleated air filters, recommendations vary from 3 months to a year.

Filters are expensive, especially the efficient varieties and the 4, 5 and 6 inch types so you don’t want to be changing them more often than absolutely necessary. It’s very difficult to know when a filter has reached the point where it is better to change it than to leave it in the system.

Manufacturers can’t really tell you because they can’t possibly know the conditions in every home, not to mention every geographic area. There are just too many variables to consider. If you follow a set schedule for your filter changes you are probably not getting the best value from your filters.

Leaving an air filter in your heating or air conditioning system too long costs money

If you don’t replace you air filter often enough it begins to impact air flow and causes equipment operating efficiency to decline. A decrease in operating efficiency translates to higher operating costs. This means higher energy bills and nobody wants that either.

If left in a system long enough, a dirty filter will cause air flow restriction and can cause evaporator coils to ice up, heat exchangers to crack, longer run times and other equipment troubles that may require a service technician.

So what’s the solution?

Installing an air filter change indicator eliminates the guessing from filter change schedules. You won’t be throwing money away by changing filters too often and you won’t be wasting money and dealing with the potential problems associated with leaving an air filter in too long.

More about air filter change indicators.

Question: Can I use a Boair 5 stage air filter with a geothermal system?  The unit is 8 1/2 years old.  I have a metal filter that you hose off just like the Boair 5 stage, but they said it would last 8 to 10 years.  My thermostat is showing it needs changed.  I did clean it and replaced it in the unit but it is still saying change.  Thank You.

Changing to a Boair 5 Stage Electrostatic Filter

If you are currently using some type of electrostatic air filter in your geothermal heat pump I see no reason not to use the Boair 5 Stage electrostatic filter instead.  They are one of the most efficient electrostatic furnace filters available.  However, without seeing your old filter, I can’t say if you need to replace it or not.

I looked at a friends heat pump the other day and he was using an electrostatic air filter with a metal frame and the filter was still in very good condition after 10 years of use.

There are Two Types of Filter Change Indicaters

Thermostat Filter Change Timers

1) This type has an electronic timer in the thermostat that is used only as a reminder to change your air filter at pre determined intervals.  Depending on the type of thermostat you are using the intervals can be based on hours of operation or days of operation.  These times are usually programmed into the thermostat when they are installed and can be adjusted later if necessary.

Every time the filter change indicator illuminates on the thermostat it must be reset so that the timing sequence begins again from zero.  Resetting these timers is typically done by pressing a button or a combination of buttons.  Sometimes they can be a bit tricky to figure out.  Every manufacturer has there own way of doing things.

These filter change indicators do no reset automatically, so you will have to reset it yourself.  If you are unsure how to reset it contact the manufacturer or a local contractor.  You may also be able to find this information by doing a search online for the manufacturer and model number of the thermostat.

If the thermostat will not reset and you are sure you are using the proper procedure, you will have to change the thermostat.  These filter change indicators are only reminders and do not indicate if the filter is actually dirty or not.  If the thermostat is working properly otherwise I would not worry about a faulty filter change indicator.  Simply replace or clean the filter every one to three months and you will be fine.

Filter Clog Switch

2) The second type of filter change indicator is the filter clog switch.  These are much better devices and are activated when the furnace filter or air conditioner filter becomes dirty.

Unfortunately these types of filter change indicators are not often used in residential heating and air conditioning equipment.  There is a higher cost associated with these filter change indicators and of course to be competitive manufacturers have to offer similar products.

These filter change indicators sense the air flow through the air handler and react to changes in air pressure within the air handler.  There are a couple of different ways that this can be done, but that is beyond the scope of this article.

Basically what happens is, as the filter becomes dirty it causes a restriction to air flow through the filter.  This restriction to air flow causes a pressure change that the filter change indicator (air flow switch) reacts to, telling you it is time to change your air filter because it is getting dirty.

There are Two Things That Can Cause This Type of Filter Change Indicator to Indicate a Dirty Filter Incorrectly

1) If the air flow switch is not calibrated properly it may indicate that the filter needs to be changed when it doesn’t or it may not indicate the filter is dirty at all, when it fact, it is time for it to be changed or cleaned.

2) The other thing that can cause this type of filter change indicator to give false readings and is relatively common in heat pumps and air conditioners that are have been in service for many years and systems that use inefficient filters, is a dirty evaporator coil.

Before making any changes to the settings of the air flow switch, inspect the evaporator coil and make sure it is not dirty and restricting air flow.  A dirty air filter and a dirty evaporator coil show the same symptoms, so if everything indicates a dirty air filter but you know it is clean, check the evaporator coil.