HVAC · July 27, 2022
If the ducts are wrong, the equipment does not matter
Airflow, static pressure, and leakage decide whether a new condenser is a comfort upgrade or an expensive noise in the side yard.
6 minute read · Anchors Aweigh Energy
We have stood in more than one garage while a brand-new condenser hummed and a bedroom at the end of the run sat four degrees off. The equipment was fine. The ducts were a 1994 afterthought wearing a 2024 condensing unit.
Three numbers
- Duct leakage. In California new systems have a HERS leakage target. Existing systems often leak enough to be a retrofit all by themselves.
- Airflow. The coil wants a design CFM per ton. Too low and you lose capacity and can ice a heat pump. Too high and you move air nobody asked for.
- Static pressure. The fan can only push so hard. Crushed flex, a dirty filter slot, and a coil that was never matched will eat the fan alive.
A duct-blaster test and a few static-pressure readings will tell you more than a brochure about SEER2. If you are replacing a system, test the old ducts before you commit to reusing them. If you are diagnosing a comfort complaint, test before you replace anything.
Bruce Cheney and the field team have been doing this work long enough to know that “the unit is too small” is the least common correct answer. Call 858-254-1189 if you want the ducts measured instead of argued about.