GFCI nuisance was replaced with systems described in 210.8(B)(4) Exception #2, even if your equipment was supplied by receptacles outdoors.
I'd use a three phase RCD or RCBO;
Thanks man! I missed that when I glanced through the code.
Is there receptacles involved that might trigger portions of 210.8 to require GFCI protection?
I feel like I have seen 'ground fault alarm' on a VFD before, you guys know way more about VFD's than me but dont they have some kinda built in magic that detects ground faults on the motor side?
Many do have built in ground fault detection on the output side, however the brand that was commonly used at the plant I did a lot of work at was set at 50% of the rated output of the drive. Not adjustable...you either enabled or disabled the ground fault protection when you set the drive parameters.
Yes they do, and in most cases if there is a ground fault on the load side circuit, the drive will shut down with "ground fault" for a fault code. If it is a motor you are trying to start, it will trip before the motor even has had any noticeable acceleration as it will pick up this fault at a pretty low voltage level during the starting ramp up.
On A-B drives, the GF trip is factory set at I think 38% of the VFD current rating... You would be LONG dead by the time that trips.
I have looked into why this is, such as RCD protected public swimming pools in Europe.
That ended with 2014 NEC Now it is 50 amp receptacles 150 volts to ground and less and includes three phase receptacles up to 100 amp and 150 volts or less to ground. I can see this causing problems with portable machines that are cord and plug connected that have a VFD within them.
That is what I was thinking, so some of what is in 210.8(A) is rather redundant language.
Yes, the Class A, is not needed in any code rule because that is covered by the definition of Ground Fault Circuit Interrupter.
We had hundreds of great Danfoss VFD'S. At least a couple times a month we would get a call one tripped out on what they called " Earth Fault ". Over 95% of the time it was a false event. Would megger the 480 volt motors with a 1,000 volt megger, inspect the splices inside pecker head and readings were good. Might be one to three year span before next false ground fault trip. Did have maybe eight out of ten outdoor Danfoss exhaust fan drives trip.out on earth fault frequently but all had great measurements. Finally asked our great Danfoss tech why we were receiving so many false earth fault trips. Told me to for a short manufacturing period they had faulty ribbon cable that came off the control boards. He replaced them for free and problem disappeared. Both Danfoss & ABB drive techs told me the ground fault pick up on their drives is different then the plain Jane GFCI residential receptacles. One told me they use an algorithm to calculate when to trip out on ground fault.
'Class A' definition relies solely on a outside (extra legal) definition in UL 943 and it really only has one problem it allows 420 cycles of the full 60Hz when your getting zapped in the 6- 29ma (North American range). Is 7 seconds really protecting anybody from anything in that range?
While the product standard does allow that long time to trip for lower level ground faults, in reality they trip pretty much instantaneously. If they actually tripped at the maximum permitted trip time you would have to hold the test button in for over 5 seconds.
