Static pressure is the resistance air encounters as it moves through your ductwork, coils, and filters. Measured in inches of water column (in. w.c.), it’s one of the most diagnostic numbers in HVAC — a properly designed system runs around 0.5 in. w.c. total external static pressure.
What high static pressure means
- Blower motor working harder, drawing more amps
- Lower CFM (airflow) — reduced heating/cooling capacity
- Frozen evaporator coils in summer
- Short-cycling and high-limit trips in winter
- Premature blower motor failure
Common causes of high static pressure
- Severely clogged filter (the #1 cause)
- Undersized return ducts
- Restrictive high-MERV filter beyond blower’s capability
- Closed dampers or supply vents
- Crushed or collapsed flex duct
- Dirty evaporator or condenser coil
Measuring static pressure is part of a proper annual maintenance visit. It tells us how the system is actually performing, not just what it’s rated for.
Related: CFM, Blower Motor, Ductwork.
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Right Way Mechanical is a family-owned HVAC contractor serving Wheat Ridge, Arvada, west Denver, and the Colorado foothills.