One potential problem with GFCI and CNC is that a VFD will trip them.
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If you find your are tripping your GDCI with the VFD, a less costly solution might be to try a 120v isolation transformer for your VFD power on the GFCI circuit…
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I put a standard light/toggle switch on the front of my CNC table and the outlets the machine and VFD are plugged into are controlled by that switch. The laptop gets a always on power outlet. I did a 4 outlet box and 2 are switched are 2 are always hot.
I have a 25ft power cord from the table to the wall, where it’s in a surge protector.
My shop is all GFI, i haven’t had any issues with the VFD.
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As stated above my Jet 1221 VS lathe trips a GFCI. I have seen reports here on the forum that the VFD sometimes trips the GFCI. I think that the lathe and the VFD when they change output causes current to change on the input and the purpose of a GFCI to so constantly compare the voltage differences between the 3 legs, ground, hot and neutral. If they see a difference between any two legs it trips a GFCI and is working properly. However the VFD and variable speed lathe are working properly they do cause a GFCI to trip and can be a problem when running a CNC. For the lathe it is just annoying and you just start the lathe up again and keep cutting.
So I would definitely use the GFCI on a VFD and only change it if you have a problem.
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