HVAC Airflow Testing

A lot of Phoenix homeowners have been told their system is fine. Refrigerant charge checks out, capacitor is good, coil is clean, and the house is still 82 degrees upstairs at four in the afternoon. That is because charge and airflow are two separate things, and most service calls only check one of them. An air conditioner can be perfectly charged and still deliver two-thirds of its rated capacity if the duct system cannot move the air. Airflow testing is how you find out. It is measurement with instruments, not a technician standing in a hallway with his hand up.

The four numbers we take

Total external static pressure is the big one. We drill test ports and read pressure before and after the air handler with a manometer. Most residential equipment is rated at 0.5 inches of water column, and we want to see under that. Plenty of Valley systems read 0.9 or higher, which is the ductwork equivalent of breathing through a coffee stirrer. CFM per ton should land around 350 to 400 in a dry climate like ours. Below 300 and the coil starts running cold enough to have freezing problems. Temperature split, the difference between return and supply air, should generally sit in the high teens to low twenties on a properly charged system, and a split that reads too wide often means not enough air moving, not a great machine. Register velocity at each outlet tells us where the air is actually landing.

What the numbers usually reveal

High static with a clean filter points to undersized returns more often than anything else. Builders in this Valley put a 14-inch return on a four-ton system for decades, and that single choking point costs the homeowner every summer since. Other common findings: flex duct kinked over a truss, a run crushed under blown-in insulation, an undersized trunk feeding a two-story build, or a coil that is restricting more than anybody realized. Low CFM to one bedroom with acceptable numbers everywhere else is usually a balance issue rather than a capacity issue, and air balancing solves that for a fraction of what people expect to spend.

Testing also protects you from buying the wrong thing. We regularly test homes where somebody has been quoted a new condenser, and the equipment is fine. The duct system is the bottleneck. Putting a bigger, more efficient unit on a duct system that already cannot breathe gets you a larger power bill and the same hot upstairs. If you have wondered why upstairs is always hotter, the answer is almost always in these numbers, combined with west-facing glass and an attic that hits 155 degrees.

What you get is a written set of readings and a plain explanation of what they mean. If sealing fixes it, we say so and quote duct sealing. If the return is the strangle point, we quote a return air upgrade. If the whole layout was wrong from the day the house was framed, we will show you the case for duct redesign rather than selling you three small jobs that never add up to a fix. And if the readings come back clean, we will tell you that too and point you at the actual cause. Flat-rate pricing before we start, no exceptions. Call (480) 863-5855 or request an estimate.