How do you set MERV‑13 filtration without wrecking blower curves—what filter area and external static targets work?
To use MERV-13 filters right, get one that allows air to flow easily. A bigger filter, like a 4–5-inch pleated one, works best because it has more surface area than the thin ones. Keep the air pressure low, around half an inch of water column, to keep your blower working well.
If you don’t use a bigger filter, the MERV-13’s resistance will mess with the air pressure and reduce airflow. Bigger filters or adding more returns can help you get clean air and good airflow without straining your system.
To set MERV-13 filtration without wrecking blower curves
Filter Area and External Static Pressure Targets
-Filter Size: Choose a filter with a larger surface area to minimize pressure drop. For example, a 20x25x2 filter has a face area of 3.47 square feet and an initial pressure drop of 0.17 inches w.g. at 1200 CFM.
-External Static Pressure (ESP): Aim for an ESP of 0.4-0.5 inches w.g. or less to ensure optimal airflow and prevent blower curve issues. Some systems may require lower ESP targets, so consult the system’s manual or manufacturer’s recommendations.