When a utility outage occurs, most facility managers naturally focus on whether the generator starts. But in reality, one of the most common reasons a building goes dark during an outage has nothing to do with the generator at all.
It’s the Automatic Transfer Switch (ATS).
The ATS is the "gateway" between the utility source and the generator. If it does not transfer load correctly, even a perfectly maintained generator with a full tank of fuel will fail to deliver power to the building. In Texas—where severe storms, extreme heat, and aging infrastructure often trigger outages—the reliability of the ATS is just as important as the reliability of the generator itself.
Despite its importance, the ATS is one of the least understood and least maintained components in many commercial and industrial facilities. This detailed guide explains the major ATS failure points, early warning indicators, and what facility and operations teams should do to identify risks before they turn into downtime.
Why ATS Failures Are More Common Than You Think
Generators get weekly or monthly test runs. ATS units? They often sit untouched for months or even years at a time. That long period of inactivity allows:
Contacts to degrade and oxidize.
Mechanical linkages to become stiff ("stiction").
Electronics to drift out of calibration.
Terminations to loosen due to vibration.
Environmental contaminants to accumulate.
This creates a dangerous situation where the ATS appears fine—until the moment it has to physically move thousands of amps of electrical load during a real crisis.
Related Reading: Learn how the ATS fits into the bigger picture of reliability in: [Link to Blog 1: Why Generators Fail: Top 7 Early Warning Signs]
1. Worn or Pitted Contacts
Every time an ATS transfers or retransfers, a massive amount of electrical energy is interrupted. This creates an arc (a mini lightning bolt) between the internal contacts. Over time, this arc activity causes pitting, carbon buildup, and surface erosion.
Why It Happens In industrial environments—especially those with high humidity or airborne contaminants—contact wear accelerates. If the contacts become too rough or pitted, they create high resistance. High resistance creates heat. Eventually, the contacts may weld shut or fail to close completely, leaving the facility with no power from either source.
Warning Signs
Audible "chattering" or clicking without full motion.
Slow transfer or visible hesitation.
Visible soot or darkened metal around the arc chutes.
Transfer failure under load.
2. Loose Electrical Terminations
Generators vibrate. Transformers hum. Buildings settle. Over time, thermal cycling (the expansion and contraction of metal as it heats up and cools down) causes electrical lugs to loosen.
The Invisible Danger Loose terminations are dangerous because they create hot spots that cannot be seen with the naked eye. A loose connection increases resistance, which generates heat, which causes further loosening—a cycle that often ends in melted insulation or a catastrophic arc flash event.
NFPA 70B strongly encourages regular torque verification and Infrared Thermography to identify these issues before they burn.
Related Reading: See how we check for these issues in: [Link to Blog 6: What a Generator Downtime Risk Assessment Includes]
3. Control Board and Logic Failures
The ATS controller is the "brain" of the operation. It constantly monitors Utility Voltage, Generator Voltage, Frequency, and Phase Rotation.
If the control board drifts or fails, it may:
Delay transfer indefinitely (waiting for a "perfect" signal that never comes).
Fail to send a start signal to the generator.
Retransfer to utility power too early, causing "short cycling."
Display nuisance alarms that confuse operators.
Warning Indicators
Frozen or blank LCD screens.
Voltage readings that do not match a handheld multimeter.
Alarm messages that appear sporadically and clear themselves.
4. Mechanical Binding in the Transfer Mechanism
Inside an ATS are mechanical parts—gears, cam assemblies, springs, linkages, and solenoids—that must move smoothly and instantly.
The "Stiction" Problem Grease dries out. Dust settles on lubricated surfaces. In Texas heat, lubricants can degrade over time. This leads to mechanical binding, where the switch physically gets stuck halfway between sources. A mechanically failing ATS might work during a "no-load" test (where there is no magnetic resistance) but fail under the stress of a real outage.
Field Indicators
Grinding or scraping noises during testing.
Jerky or incomplete motion.
The switch handle feeling "stiff" during manual operation.
5. Environmental Contamination
Texas industrial environments are tough on electrical equipment. Dock doors stay open, forklifts stir up dust, humidity fluctuates, and metallic dust from machining operations can drift into enclosures.
Common Contaminants:
Dust: Acts as an insulator, causing overheating.
Moisture: Leads to corrosion on control wires.
Rodents: Mice and rats love the warmth of ATS enclosures and often chew through sensing wires.
6. Safety Consideration: ATS Work Requires Proper PPE
This is critical for Facility Managers to understand: The ATS is almost always energized.
Unlike a generator, which can be turned off and locked out, an ATS typically has live Utility power on the top lugs and live Generator power on the bottom lugs. Working inside the enclosure exposes technicians to:
Live Conductors (480V or higher).
Arc Flash Hazards.
High-Ampere Interrupts.
Never attempt to service an ATS yourself. Proper PPE (Personal Protective Equipment), Arc Flash suits, and specialized insulated tools are required by OSHA and NFPA 70E standards.
How to Identify ATS Problems Before They Cause Downtime
The key to ATS reliability is proactive inspection, not reactive troubleshooting.
1. Infrared Thermography (IR Scanning)
Thermal imaging is the gold standard for ATS maintenance. It allows technicians to see heat signatures caused by loose lugs or worn contacts while the system is energized, without touching live parts.
Related Reading: IR scanning is also critical for your generator. Read: [Link to Blog 1: Why Generators Fail: Top 7 Early Warning Signs]
2. Functional "Transfer" Testing
Mechanical exercise is vital. This often requires coordination with operations teams, but it helps verify:
Transfer speed.
Linkage alignment.
Solenoid performance.
In-phase monitor calibration.
If the ATS hesitates during a scheduled test, it will almost certainly fail during an emergency.
3. Reviewing Alarm Logs
Most modern ATS controllers store event histories. Small anomalies—like a "Fail to Transfer" error that happened at 3:00 AM three months ago—are often early warnings of a dying solenoid or logic board.
Related Reading: Reviewing logs is part of a Load Bank Test strategy. Read: [Link to Blog 3: How Often Should Industrial Generators Be Load Bank Tested?]
4. Voltage Sensing Verification
If the ATS thinks the Utility voltage is 460V but it's actually 480V, it may refuse to transfer. Calibrating the sensing inputs ensures the "brain" is making decisions based on reality.
Related Reading: Irregular frequency from the generator can also confuse the ATS. Check out: [Link to Blog 5: How Fuel Quality Affects Generator Reliability]
Conclusion
The ATS is the critical link between your generator and your facility’s electrical loads.
Worn contacts, loose terminations, control logic issues, mechanical binding, or environmental degradation can all undermine transfer performance. A generator that starts but cannot reach the building is useless.
Proactive inspection, proper diagnostics, and structured preventive maintenance help reduce risk and support reliable emergency power operation, especially in demanding Texas industrial environments.
To schedule an ATS inspection or a facility power reliability review, reach out to the professionals at Texas Industrial Infrastructure Services.