Choosing an air filter for your house or furnace should be easy, right,
the truth is…..not really, every house and system have a different need and it’s not complex.
Factors to consider for your Charlotte home
It depends more on the occupancy of the house and if the duct system was properly sized during installation. Let’s look first at occupancy, the amount of people, pets and traffic will tell you what you need and how often to change the filter. If you have a bustling household, 2.5 kids a dog a cat, a llama, and the door to the outside is constantly swinging open and closed you will need to change your filters every 20-30 days. If you have a residence that has very little traffic and no pets, you can get away with 45 to 60 days, no more. Now let’s address this change the filter every 3 months filter mentality, it only applies to the last scenario, pretty much a house that has little or no physical disruption. For the rest of us with Llamas it must be done every 30 days at a minimum. You may ask, David what filters do you recommend, ah, great follow up question, being a Licensed HVAC technician in both North and South Carolina, I have seen some disgusting filters, evaporator coils and blower motors from people not even having a filter in the system. I base this article on my observations on the complete envelope of the house, occupants, animals, duct design and integrity, and condition of the house, if you have an active, hose with pets, please buy inexpensive pleated filters, not fiberglass filters, don’t worry about the MERV rating, no brand names, 3 for $10 at any box store and change them every 20 – 30 days. If you have a quiet 2-person home, same thing but change them every 45 days. Now let’s get to allergies and MERV ratings (Minimum Efficiency Reporting Value), the higher the MERV rating the smaller the airborne particulate it can catch, MERV 8 is more than sufficient for people with out allergies. People with allergies or respiratory issues will need to have filters installed with a rating of between 11 and 16, these filters tend to be more expensive but do provide a healthier home.
High efficiency filters can cause damage to your heating and air conditioning system in Charlotte
There is a drawback to the higher MERV rated filters, if the duct system is not sized properly for the house, these filters can and will shorten the life of your system. Inside of your furnace is a blower motor that can push and pull a certain amount of air through the house, lets call this amount X, when the system in the house was sized and installed in your house, the installation company was required to make sure the air flow in the house was correct. Remember X, the motor, well X needs Y, Y is TESP (Total External Static Pressure), it is a measure of resistance, the required TESP is on a label inside the furnace and typically it is around .5 and any thing from .5 to .8 is acceptable. To complicate matters newer homes, have a blower motor called an ECM motor, it uses less electricity than the older motors and can overcome some design flaws but also uses more amperage to overcome these flaws and dirty filters, and the dirtier the filter the hotter the motor gets until it fails. this is the main reason I want homeowners to use MERV 8 filters.
Trust Your Local HVAC Company in Charlotte
It has been my experience, the experience of the technicians, fellow HVAC competitors and the industry that TESP (Total External Static Pressure) being incorrect, is the leading reason to higher electric and gas bills and premature failures of a system.
If you are having your system regularly maintained your HVAC provider should be able to tell you what your TESP is and what filters you should buy. If your technician tells you the TESP is above 1. You need to find out why and have the duct work assessed.
When NASCAIR is asked to replace a system, the first thing we check is the size of the return duct on the back of the furnace, if it is not sufficient, we will let the homeowner know that we can’t give them a quote unless they address the air capacity need for the system, they may say it worked great for 20 years so why not now, same reason we do not have rabbit ear antennas, we have cable or fiber, its more reliable and efficient but needs a very strong support structure.