Rooftop unit economizer not working (most offices have this and don't know)

What this error means

Here's a statistic worth knowing if your office sits under a rooftop unit: field studies have repeatedly found that 60–80% of RTU economizers — the dampers that should be cooling your office with free outside air — are not working properly (64% in NBI/PIER field research, 80% in PG&E's study of existing units, ~two-thirds across studies compiled by ACEEE and New Buildings Institute). A failed economizer doesn't break your AC; it silently runs the compressor when outside air would do the job, wasting $1,000–$3,700 per unit per year by DOE-cited estimates.

Symptoms

• Cooling bills higher than comparable spaces
• Compressor running on mild days when outside air is cool
• Stuffy air / complaints about freshness (stuck-closed dampers also starve ventilation)
• Nobody has serviced the RTU in years

Try this first (safe DIY steps)

1. This one isn't DIY (it's on the roof, and it's linkage, actuators, and controls) — but you can ask the right question: request an economizer function test on your next service visit; most PM contracts skip it
2. Ask specifically: do the dampers stroke fully open and closed, and does the changeover logic work?

Safety: power off before any physical intervention. Never bypass covers or interlocks — fuser areas run hot enough to burn.

When to call a technician

Economizer/damper actuator repair typically runs $120–$650 installed — often paying for itself within the year in energy savings.