What We Found When Inspecting Inefficient Economizers on Commercial Rooftop Units

Commercial rooftop HVAC units with economizers installed—systems like these require regular inspection to ensure outside air dampers and controls are operating efficiently.

Owens Companies was recently contacted by a facilities manager who oversees several large commercial buildings across the Twin Cities. Many of those buildings rely on rooftop HVAC units equipped with economizers, which are designed to reduce cooling costs by using outdoor air when conditions allow. Despite having preventive maintenance in place, the facilities team had grown dissatisfied with how the systems were performing—and with the level of detail they were receiving from their current maintenance provider. Energy costs seemed higher than expected during mild weather, and they suspected the economizers weren’t doing what they were supposed to. They asked our team at Owens Companies to take a closer look and help determine what might be causing the issue.

Rooftop Unit Economizers Not Operating Properly

During our inspection of the rooftop units, we discovered that several economizers were not operating as intended. In some cases, the outdoor air dampers were stuck closed, preventing the system from bringing in cooler outside air. In other units, sensors had drifted out of calibration and were incorrectly signaling that outdoor conditions weren’t suitable for economizer operation.

We also found an actuator that had failed, which meant the damper never moved when the system called for economizer mode.

None of these issues had caused the HVAC systems to stop working entirely. The buildings were still being cooled. But the rooftop units were relying on compressors instead of using outdoor air when conditions allowed—eliminating the efficiency benefit the economizers were designed to provide.

Why Economizer Problems Often Go Unnoticed

Economizers are one of the most valuable efficiency features in commercial HVAC systems, but they are also one of the most commonly overlooked components.

When an economizer fails, the system usually continues operating. Occupants still feel comfortable, and there may be no immediate alarm indicating a problem.

However, behind the scenes, the system may be:

• Running compressors when outdoor air could provide cooling

• Bringing in too little or too much outside air

• Allowing humid air into the building

• Increasing overall equipment run time

Over time, these issues can lead to higher energy costs and additional wear on mechanical equipment.

Economizer damper assembly from a commercial rooftop unit. Components like these must operate correctly for economizers to provide energy-saving “free cooling.

Common Rooftop Unit Issues We See in Commercial Economizer

The issues we found during this inspection are ones we see frequently across commercial facilities.

Some of the most common economizer problems include:

Stuck Rooftop Unit Economizer Dampers

Mechanical dampers that control outside air intake can become stuck due to wear, corrosion, or debris.

Failed Actuators

Actuators control the movement of the dampers. When they fail, the dampers may remain open or closed regardless of system demand.

Sensor Calibration Problems

Temperature or enthalpy sensors determine when outside air conditions are suitable for economizer operation. If sensors drift out of calibration, the system may never enter economizer mode.

Control Sequence Issues

Improper control settings or programming can prevent the system from switching between mechanical cooling and economizer operation.

What We Did to Restore Proper Operation

After identifying the issues, our technicians repaired the failed components and recalibrated the systems so the economizers could operate correctly again.

This included:

• Repairing damper assemblies

• Replacing a failed actuator

• Calibrating outdoor air sensors

• Verifying economizer changeover settings

• Testing system response under different operating conditions

Once the systems were functioning properly again, the rooftop units were able to take advantage of cooler outdoor air conditions as intended.

Why Economizer Inspections Matter

Economizers are designed to reduce cooling costs and improve ventilation in commercial buildings. But like any mechanical component, they require periodic inspection and maintenance to operate effectively.

Without regular testing, it’s easy for economizers to fall out of calibration or develop mechanical issues that prevent them from delivering the energy savings they were designed to provide.

For facilities with multiple rooftop units, even a few malfunctioning economizers can significantly impact overall energy performance.

Economizer Service for Commercial HVAC Systems

At Owens Companies, we regularly inspect economizers as part of commercial HVAC maintenance programs for facilities across the Twin Cities. Our technicians test damper operation, sensor calibration, and control sequences to ensure systems are operating efficiently and responding properly to outdoor conditions.

If your building relies on rooftop units with economizers, periodic inspection can help ensure the system is delivering the energy savings it was designed for.

Schedule Economizer Service

To learn more about economizer inspection or commercial HVAC maintenance, contact Owens Companies to schedule service with our team.

Frequently Asked Questions About HVAC Economizers

What does an NVAC economizer do?

An HVAC economizer helps a commercial system reduce cooling costs by bringing in cooler outdoor air when conditions allow, instead of relying entirely on mechanical cooling.

How do I know if an economizer is not working?

Common signs include higher-than-expected energy costs, rooftop units running mechanical cooling during mild weather, dampers stuck open or closed, humidity issues, or inconsistent system performance.

Why do economizers fail?

Economizers often fail because of stuck dampers, failed actuators, sensor calibration issues, worn linkages, or control sequence problems. Many of these issues go unnoticed without routine inspection.

Can a faulty economizer increase energy costs?

Yes. If an economizer is not operating properly, the system may run compressors more often than necessary or bring in outside air at the wrong time, which can increase energy use.

Should economizers be included in preventive maintenance?

Yes. Economizers should be inspected as part of a commercial HVAC preventive maintenance program to verify damper movement, sensor calibration, actuator performance, and control operation.

Does Owens Companies inspect economizers on rooftop units?

Yes. Owens Companies inspects economizers as part of commercial HVAC maintenance and service programs for facilities across the Twin Cities.