GFCI Nuisance Tripping Puzzle Needs a Solution

[Lipidome]

I recently purchase a new 110v AC powered lathe with a manufacturer’s recommendation for a 20 amp circuit. The lathe is driven by a DC motor that is powered by the AC circuit. I installed the circuit in the shop to include the GFCI in the entrance panel. The building inspector not only approved the work, he congratulated me on the quality of the work. When the work was signed off (I had not tested it beyond confirmation that the hot/neutral/ground were correct) prior to final inspection. When I connected the lathe to the circuit and started it up the GFI tripped. I disconnected the lathe and tried other power tools (power saw, drill, etc.) and all of them worked fine without tripping the breaker.

In desperation I removed the GFCI from the entrance panel, replaced it with a standard 20A breaker and the lathe operates perfectly with the GFCI out of the circuit. I then installed a GFCI duplex at the outlet for the lathe. Same results. Starting the lathe tripped the GFCI duplex but all of my other power tools functioned as they should from that same source. Quite obviously, I can run the lathe without benefit of a GFCI - but that’s not the right way to handle this and I haven’t been able to find any guidance on how to correct the problem.

I would prefer not to experiment. Any ideas ...

 

[Little Bill]

I am closing this thread, in accordance with the Forum Rules.

This site is designed for:

• Electrical Contractors
• Electricians
• Engineers
• Inspectors
• Instructors

* This NEC Forum is for those in the electrical and related industries. Questions of a "How-To" nature by persons not involved in the electrical industry will be removed without notice.
Reminder to all members, if you see a questionable post, feel free to report it by clicking "Report" at the bottom left corner of the post.