How to Troubleshoot a Faulty Commercial Standby Generator

Introduction

Standby generators are essential backup systems that provide emergency power when the main power source fails. Commercial standby generators are large units designed to supply emergency power to businesses, hospitals, data centers, and other facilities. Like any complex machine, standby generators can develop issues that prevent them from operating properly when needed. As the owner or operator of a commercial facility, it's important to understand how to troubleshoot common standby generator problems so you can quickly restore backup power if the main utility supply goes down. This article provides a step-by-step guide to diagnosing and resolving the most frequent causes of standby generator failures.

Safety Precautions

Before beginning any troubleshooting or repair work on a commercial standby generator, it's critical to follow safety protocols. Generators contain dangerous high voltages and moving parts that can cause severe injury if proper precautions aren't taken.

• Always turn the main generator breaker to the "off" position before inspecting or servicing the unit.
• Allow sufficient time for residual voltage to dissipate before working on the generator.
• Use proper lockout/tagout procedures to prevent the generator from being started while maintenance is in progress.
• Wear insulated gloves and other personal protective equipment when testing live circuits.
• Do not wear loose clothing or jewelry that could get caught in moving parts.
• Check that all covers and guards are in place before restoring power to the generator.

Basic Troubleshooting Steps

Begin basic generator troubleshooting by following these steps:

Inspect the Generator Exterior

• Check for any visible external damage, leaks, or loose connections. Faulty wiring or plumbing connections can prevent startup.
• Look for debris buildup around intake and exhaust vents as this can impede airflow.
• Ensure all access panels are properly secured. Loose panels may allow water ingression leading to shorts.

Check All Fluids

• Engine oil level - Low oil can prevent starting or cause engine damage.
• Coolant level - Insufficient coolant will lead to overheating.
• Fuel supply - Verify the day tank has sufficient diesel fuel. Main tank may be empty.

Review Maintenance Records

• Check for overdue routine maintenance like air, oil, and fuel filter changes which can cause no-start issues.
• Review recent repair and overhaul work that could be related to current problem.

Inspect Batteries

• Loose battery cables and corroded connections are common causes of failure to start.
• Check battery voltage with a multimeter. Voltage should be 12+ volts.
• Consider load testing the batteries if voltage is borderline.

Check Control Panel

• Scan the panel for any fault codes or alarm indicators that may point to the failed component.
• Reset the panel by turning off power completely, waiting a minute, then restarting.
• On microprocessor-based generators, check for any diagnostics codes displayed.

Common Standby Generator Faults

If basic troubleshooting steps don't uncover the issue, consider these frequent generator malfunctions:

Failure to Crank

The starter motor fails to turn over the engine when the generator is signaled to start.

• Causes
• Defective starter motor
• Low/dead starting batteries
• Seized engine from prolonged inactivity

• Defective starting circuit relay or contacts

• Solution

• Check starter wiring and connections
• Test starting batteries and recharge if needed
• Check starter relay operation
• Remove starter and have it tested at repair shop

Failure to Start

The starter motor cranks but the engine doesn't start.

• Causes
• Out of fuel
• Clogged/dirty fuel filters
• Fouled/defective fuel injectors

• Low compression

• Solutions

• Fill day tank and bleed fuel system
• Replace fuel filters
• Test injectors, clean or replace
• Perform engine compression test
• Check for low oil level

Surges and Fluctuations

Engine runs irregularly with oscillations in voltage and frequency.

• Causes
• Governor malfunction
• Fuel starvation
• Defective/dirty injectors

• Exhaust leaks

• Solutions

• Inspect and adjust governor
• Clean/replace fuel filters
• Service injectors
• Check exhaust system seals

Overheating

Engine constantly runs hot; temperature gauge in red.

• Causes
• Coolant leak
• Radiator fins clogged with debris
• Faulty water pump
• Thermostat failure

• Coolant flow restriction

• Solutions

• Check coolant system for leaks
• Clean radiator fins carefully
• Test water pump operation
• Replace thermostat
• Flush cooling system

No AC Output

Generator runs but won't supply AC power.

• Causes
• Tripped main breaker
• Faulty transfer switch
• Defective power windings

• Shorted generator leads

• Solutions

• Reset main breaker
• Test transfer switch controls
• Check windings with multimeter
• Inspect leads and terminal connections

Unusual Noise/Vibration

Generator has grinding, knocking, squealing, or shaking while running.

• Causes
• Loose or broken engine mounts
• Defective bearings
• Misaligned coupling
• Unbalanced rotating parts

• Exhaust leak

• Solutions

• Check and retorque engine mounts
• Test crankshaft and bearing endplay
• Realign coupling
• Inspect fans and couplings
• Check exhaust system hangers and leaks

When to Call for Generator Service

For major generator problems like seizing engines or significant electrical faults, the best option is to contact the generator manufacturer or an authorized service dealer. Most manufacturers provide 24/7 emergency service for critical standby power systems. Trained technicians have the expertise to fully evaluate and repair complex generator malfunctions beyond typical operator troubleshooting capabilities.

Conclusion

Regular standby generator testing and maintenance is the best way to prevent failures when emergency power is needed. But even well-maintained generators can experience issues. Knowing how to perform basic troubleshooting steps can help minimize downtime. For significant generator problems, don't hesitate to call the manufacturer's service department to get your backup power running again quickly. Proper generator maintenance and servicing will ensure your system provides reliable emergency power for years to come.