CSLB C-20 HVAC ContractorVentilation and Air DistributionMedium
A technician replaces a MERV 8 filter with a MERV 13 filter of the same physical dimensions, without modifying the blower or ductwork. What is the most likely operational result?
- ADecreased latent cooling capacity caused by lower filtration efficiency
- BIncreased pressure drop across the filter, reducing overall airflow
- CNo measurable change in system performance
- DImproved airflow due to superior filtration efficiency
Show answer & explanationAnswer & explanation
Correct answer: B. Increased pressure drop across the filter, reducing overall airflow
Higher-MERV filters have denser media that restrict airflow more than lower-MERV filters of the same size, increasing static pressure and reducing CFM delivered to the coil, which can lead to coil icing or reduced capacity.
Why the other options are wrong
- A. Latent capacity issue is a downstream symptom, not the direct/primary result described.
- C. A significant change occurs due to increased filter resistance.
- D. Higher MERV restricts airflow rather than improving it.
MERV vs Pressure Drop
Higher-MERV filters have finer media that increase resistance to airflow, raising static pressure if the system was not designed for it.
- Same-size filter, higher MERV = more restriction.
- Can cause reduced CFM, coil freezing, or blower strain.
- Media surface area and depth can offset restriction in properly designed filters.
Memory trick: Finer filter, harder to breathe through.