Frequently Asked Questions About GFCI Tripping Issues on Welder/Generators | MillerWelds

Frequently Asked Questions About GFCI Tripping Issues on Welder/Generators

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Is frequent GFCI tripping on your welder/generator causing troubleshooting headaches? Get tips to help resolve these issues.
Operator grinds on a jobsite with an engine-driven welder/generator in the foreground

GFCI tripping causes

Do you have problems with GFCI power receptacles on your welder/generator? Ground fault circuit interrupters, or GFCIs, are a safety feature on Miller® engine-driven welder/generators.

As a power receptacle where operators plug in tools, lights and other jobsite accessories, GFCIs are fast-acting circuit interrupters designed to shut off electric power within as little as 1/40 of a second in the event of a fault. They protect operators from electric shock.

GFCIs work by comparing the amount of current going to and returning from equipment along the circuit conductors. If the amount going differs from the amount returning by approximately 5 milliamperes, then the GFCI trips the circuit and removes power from the receptacle. The receptacle can be easily reset once the fault is cleared.

The design standard for GFCIs, as well as OSHA regulations and standards, have evolved over time. GFCIs now regularly self-test and have indicating lights showing their state. OSHA and the National Electric Code require GFCIs for workers using temporary wiring. To meet the new requirements, GFCIs are more complicated.

Depending on the type of GFCI being used — and the age and condition of the tools plugged into the receptacle — some users experience problems with frequent GFCI trips or even failures.

Get answers to common questions about GFCIs and tips for optimizing performance.

Q: Why do GFCIs trip on welder/generators?

A: Most welder/generators are designed so the engine idles when there is no load (welding or power) on it. This saves fuel and reduces jobsite noise.

GFCIs are designed to work at 120 volts. However, idling can lower the generator voltage and frequency. This can cause nuisance tripping and impact the life of the GFCI. 

Newer GFCI receptacles used in Miller welder/generators are designed with better built-in protection and filtering to help prevent the GFCIs from being damaged when they are reset — particularly at the lower voltage and frequency caused by idling. Because Miller uses GFCIs designed specifically for use in welder/generators, the GFCIs do not have the same failure rate as those designed for residential use. 

Q: How do my tools play a role in GFCI tripping and performance?

A: The tools and equipment being plugged into the GFCI receptacle can have an impact on how often it is tripped. If tools like a drill or grinder are old or have damaged cords, there can be current leakage from the line to the neutral or the ground, causing the GFCI to trip.  

Operators may think this is a GFCI problem when it is actually an issue with the tools or equipment being plugged in. Older equipment that is frequently tripping the GFCI should be replaced or repaired to avoid this problem and the potential shock hazard.

Q: How long should a GFCI last?

A: How often a replacement is needed depends on how the machine is used and what kind of environment it is used in. Paying attention to whether a particular tool is causing GFCI problems may prevent unnecessary replacement of a good GFCI receptacle. The weather conditions — particularly rain or moisture — can also impact the life of the GFCI.

Q: How do I know when to reset or test my GFCI vs. replacing it?

A: GFCIs that are built to the new standard have an indicator light that alerts you to necessary service. A light glowing green means the GFCI is ready to go. A blinking red light means the GFCI needs to be reset by pushing the reset button. A solid red indicator light means the GFCI needs to be replaced. 

A GFCI that doesn’t reset even when you push the reset button means it is time for replacement. Most manufacturers recommend testing GFCIs monthly. Always check the machine owner’s manual for information about testing and resetting the GFCI on your welder/generator.

Q: At what speed should I run the welder/generator when I’m testing or resetting the GFCI?

A: The engine drive should be set to run at full speed when you are testing or resetting the GFCI. Be aware that full speed can differ for each machine. 

If your machine has an ignition switch, make sure it’s set to the RUN position. If your machine has speed-governing features, such as Auto-Speed™ technology (found on Miller welder/generators) or Auto Start/Stop technology (found on EnPak® integrated truck solutions), go into the menu and turn on full run speed. This ensures the generator is putting out the full 120 volts at 60 hertz that the GFCI is designed for when it’s being tested or reset.

Q: How do I replace the GFCI?

A: Only qualified persons should install, operate, maintain and repair GFCIs. A qualified person is defined as one who, by possession of a recognized degree, certificate or professional standing, or who by extensive knowledge, training and experience, has successfully demonstrated the ability to solve or resolve problems relating to the subject matter, the work, or the project and has received safety training to recognize and avoid the hazards involved.

On Miller welder/generators, for example, the same GFCI receptacle is used in different welder/generator models but there are different ways of replacing the GFCI depending on the front panel design. Always read and follow all labels and the owner’s manual carefully before installing, operating or servicing the unit. Read the safety information at the beginning of the manual and in each section.

Q: How do I choose GFCI replacement parts?

A: Using quality OEM parts when having the GFCI replaced helps optimize performance and life. OEM GFCI receptacles are designed to work on that specific machine so it can operate at idle and full speed and not be damaged by lower voltages.

GFCI troubleshooting tips 

Paying attention to how often and when your GFCI receptacle is tripping and following best practices for testing and resetting the GFCI can help reduce tripping occurrences — saving valuable time on the jobsite. 

Learn more about welder/generator solutions and technologies from Miller.