3 Practical Tips For Troubleshooting HVAC Economizer Logic and Hardware

If your economizer isn’t taking advantage of the spring weather, try these tips for Troubleshooting HVAC Economizer logic and hardware to get your free cooling back on track.

When the outside air is crisp, cool, and low in humidity, your economizer should swing open to pull that perfect air inside, giving your energy-hungry compressors a well-deserved rest. But what happens when the system’s logic fails? Your chillers kick on, your building wastes energy, and you end up paying for mechanical cooling when you don’t need to.

1. Check your sensors

Faulty sensor data sends mixed signals

Your economizer’s logic is only as good as the data it receives. The controller relies on Outside Air Temperature (OAT) and/or return air enthalpy sensors to determine if the outdoor conditions are suitable for free cooling.

If a sensor is out of calibration, reading too high, or completely failed, the controller might think it’s a muggy July afternoon instead of a breezy April morning. As a result, the economizer stays shut.

The Fix:

Verify your sensor readings against a calibrated handheld psychrometer. If your outside air or return air sensors are drifting or unresponsive, it’s time to swap them out.

BAC Pro-tip: We stock incredibly accurate Belimo enthalpy and temperature sensors that integrate seamlessly into your existing sequence of operations.

2. Test your physical components

Is the economizer damper actuator stuck?

Sometimes the logic is perfect, the controller sends the signal, but nothing happens. Why? Because the physical dampers are stuck.

Actuators bear the brunt of the physical labor in an economizer setup. Over years of enduring the elements, mechanical linkages can bind, and actuator motors can strip or burn out. If the damper can’t open, your free cooling is dead in the water.

The Fix:

Override the system and command the economizer 100% open, then 100% closed. Go up to the roof or into the mechanical room and visually inspect the damper. Is it moving smoothly? Is the actuator whining but failing to turn the shaft? If it’s dead, you need a replacement you can trust.

As the #1 Belimo Platinum distributor in New England, we have a massive warehouse full of direct-coupled Belimo damper actuators ready to go.

3. Check your logic

Controller changeover setpoints can lock out free cooling

If the hardware passes the test, it’s time to look at the brain of the operation: the controller’s sequence of operations.

Often, economizer logic fails simply because the changeover setpoints are overly conservative. For example, if your dry-bulb high limit is set to 55°F, your economizer will lock out the second it hits 56°F—leaving a massive amount of viable 60°F free cooling completely unused!

The Fix:

Review the logic parameters in your building automation system (BAS) or standalone controller. Adjust your changeover setpoints (whether dry-bulb or single/differential enthalpy) to safely maximize the use of outdoor air without introducing excess humidity.

Frequently Asked Questions: HVAC Economizer Troubleshooting

How often should I test my economizer damper actuators?

Facility managers should test their economizer damper actuators at least twice a year—ideally in the early spring before cooling season begins, and again in the autumn. A full stroke test (0% to 100%) ensures the mechanical linkages aren’t binding.

What is the ideal changeover setpoint for free cooling?

While it varies based on the building’s internal load, a typical dry-bulb changeover setpoint for commercial buildings is around 60°F to 65°F. However, using differential enthalpy sensors is usually far more efficient than relying on dry-bulb temperature alone, as it factors in outdoor humidity.

Get Ready for Cooling Season with Boston Aircontrols

Spring is fleeting, and so is the window for optimal free cooling. Don’t let bad logic, a drifting sensor, or a busted actuator inflate your facility’s energy bills this season.

At Boston Aircontrols, we’ve been helping facilities stay efficient for over 25 years. Whether you need a simple relay, a replacement sensor, or a complete economizer retrofit package, we know our parts inside and out.

Browse our massive inventory of HVAC controls online, or contact us today to get exactly what you need shipped straight from our local warehouse!