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How To Pick The Proper Air Filter For Your Furnace and Air Conditioner

carrier_air_filter_filccBuying filters for your HVAC system may seem like an afterthought to many – like fertilizing is to lawn mowing, or flossing to your tooth brushing routine. But if you know us here at Stay Comfy Minnesota, having a clean filter is the first rule to keeping your HVAC system running properly. It’s time to make it become the first thought in keeping your home comfortable and safe by learning how to pick the proper filter for your furnace and air conditioner.

There Are Multiple Choices, What Do I Do?

Making a trip to your local hardware store to pick out a filter can be daunting. There are so many types and brands to choose from, and it’s not like picking out clothes. A silky yellow, sweetheart-cut filter is something that just doesn’t exist. You can’t base your choice on looks and aesthetics – you need to base your choice on what works best with your HVAC system. So how do you know?

“When in doubt, go with the least resistant to airflow,” says Keith Hill, technical support manager for Minnesota Air. “That’s the one with the lowest MERV rating.”

You can read all about MERV ratings and more in our Air Filters 101 Guide, but basically a MERV rating is how effectiveness is measured for air filters. The higher MERV rating means that it provides better filtration – something that usually also comes at a higher cost. A low MERV rating means it provides better airflow.

Keith says everyone wants cleaner air, but “high efficiency” in a filter also means more restrictive to airflow. 

“If the restriction is great enough, the low airflow causes all sorts of trouble in both cooling and heating modes. Restricted air in cooling mode may cause the A-coil to freeze – and if left to run long enough in that condition, that may damage the compressor,” he says. “In heating mode, the low airflow can cause the furnace to run hot, and may lead to premature heat exchanger failure.”

Don’t Believe The Hype

The first job for your filter is to protect the furnace and air conditioner coils from dirt and debris. Filtering the air to improve air quality comes second.

Keith says with so many choices – and with a lot of it being hype and buzzwords to upsell – the best bet is to pick a filter that is similar to what came with the system.

If you want to improve the air quality, you can buy a better filter. Filters that are 4” or 5” thick will be better, but may need some duct modifications to make it work.

It’s a good idea to consult an HVAC pro to verify your airflow is adequate with the new filter and that it fits properly. 

“The tech will tell you whether or not it is suitable for your system.  And if it’s not, he or she can make recommendations of ways to make it compatible,” says Keith. “It may require using a larger filter which would require minor duct changes or a different style of filter.”

In the end, you may be happier because a thicker filter needs to be replaced less often and allows for better airflow – leaving you with more time to fertilize and floss.

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