An economizer brings in outside air for cooling when the outside air is cooler than the return air. Facility managers in Phoenix assume that is never. It is more often than they think.
The hours
Phoenix has roughly 2,500 to 3,000 hours a year when outside air is cool and dry enough to cool an office building without running the compressor: nights, early mornings, and most of November through March during the day. For a building that runs 6am to 7pm, that is a meaningful share of the cooling season.
Why they do not work
Because they were never commissioned. In our retro-commissioning studies, roughly half of the economizers we test are not functioning: dampers wired shut, actuators failed, sensors reading wrong, or the controls were never told the unit had one. The energy code requires them; nobody requires them to work after inspection.
What it is worth
A working economizer on a 20-ton unit in an office saves on the order of 10–15% of that unit's annual cooling energy. Across a roof of ten units that is real money, and the repair is usually an actuator and an afternoon.
The ask
If you have a maintenance contract, ask for the economizer check in the quarterly report. If the report does not have one, that is a different problem.
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Tell us about the building. We will come measure it.
A project manager replies the same business day. Maintenance clients reach a technician on the 24-hour line.