If a filter drier becomes clogged, what symptom would you expect?

• A. The pressure drop across the drier exceeds 2 psig
• B. The system charge increases
• C. The condenser pressure drops
• D. There is no impact on performance

Answer: (A)

When a filter drier becomes clogged, it creates a restriction in the liquid line. That restriction causes a larger difference in pressure between the inlet and outlet of the drier—the pressure drop across it increases. In practice, this drop can exceed a small threshold (such as a couple of psi), and that increased pressure drop is a clear sign the drier is blocked and needs replacement. The refrigerant charge wouldn’t suddenly rise just from a clogged drier, so a system charge increase isn’t a typical symptom. Likewise, condenser pressure isn’t directly driven by a clogged drier—the high-side pressure is more influenced by condenser conditions and overall system load—so a drop there isn’t the usual indicator. And while the system will lose some performance due to restricted liquid flow, the most immediate, testable symptom you’d look for is the increased pressure drop across the drier.