The air filters for your HVAC system, whether for heating or cooling, are your first line of defense against higher energy consumption and repairs. Dirt is the main cause of furnace or air conditioner failure, and the sole job of the filter is to stop it before it enters your blower. Keeping a supply of filters on hand helps you make those changes quickly and exactly when you need to.
You have options when it comes to the air filters you use for your system. Filters carry ratings called MERV, which stands for minimum efficiency reporting value, and it’s a measure of the size of particles that the filter traps. The scale runs from 1 to 16 for residential use; the higher the rating, the smaller the particles that the filter traps.
While it’s better to trap more airborne particles for the health of your HVAC system and your breathing, there’s a limit to the MERV rating that your blower can handle. Check your owner’s manual to learn the maximum value. If it doesn’t state it, ask an HVAC technician or the manufacturer for the highest MERV-rated filter you can use.
Be sure that the filter fits the frame precisely. Your blower works like a big vacuum and it pulls air wherever it can get it. If the air filter doesn’t fit precisely in the frame, you’re bringing in unfiltered air, causing damage to your HVAC system. Dirt that enters your blower can create problems by collecting on the heat exchanger or evaporator coil.
Dust on these parts makes them work less efficiently, and in the case of the heat exchanger, can actually cause it to crack, emitting carbon monoxide into your home, prompting an expensive repair or replacement. If a utility or HVAC technician detects cracks, he is legally bound to shut down your furnace until it’s fixed. When an air conditioning evaporator coil is dirty, your compressor may run outdoors continually, eventually causing system failure.