What Does 18x20x4 Mean in An HVAC Air Filter and Why It Matters?
If you’ve ever stood in front of a wall of HVAC filters wondering what 18x20x4 actually means, you’re not alone — and the answer goes beyond simple measurements. At ThermixHVAC.com, we’ve seen firsthand how choosing the wrong filter size can reduce system efficiency, restrict airflow, and even cause long-term damage to your HVAC unit. Based … Read more