Motor control circuit tripping GFCI receptacle

Status
Not open for further replies.
Ok this may take a little to unpack and explain but i’ll Give it a try.
I recently purchased and old style large bandsaw that originally had a 3phase motor and motor starter with 110v starter coil. The previous owner had already replaced the motor with a 1.5 hp 120v motor and had reconfigured the wiring and was using the original selector on off switch to power the motor while it did work and did not trip the GFCI receptacle it was plugged into I did not like this setup and all the current flowing throw the low amperage selector switch. So since there was a contactor still available I rewired the saw back to original utilizing the motor starter. Now when I push the start button 8 out of 10 times it trips the GFCI receptacle the other 2 times everything works perfectly. The saw is plugged into a 20 amp circuit that is protected by a 20amp P&S GFCI receptacle. Your help and invite is appreciated
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Sounds like the inductive kick from the starter coil is messing with the GFCI. It's not a ground fault. Try another brand receptacle. There is a big long thread here analyzing a particular GFCI receptacle for this very problem. Do you need a GFCI receptacle because of the location?

-Hal
 
Yes the circuit should be GFI protected. If it was just me in my shop I may omit the GFI but since my sons are in my workshop with me... I will not be having that explanation with my wife if something happens to one of our sons. Much less being an electrical contractor and a firefighter... I can see the headlines now whether something bad happens to my kids or myself.
 

Toller

Member
Location
NY
I have a very similar problem...

I have a very similar problem...

I have a variable speed lathe that converts to 3phase for the speed control. It trips my GFCI outlet. I have tried 2 different brands, but they both do it. I have "fixed" it by removing the GFCI. While it seems perfectly safe to me, I prefer to do things properly. Any hope here?
 

micabay

Appliance Tech
Location
Kitsap, WA
Occupation
Appliance Tech
As motors get older, they tend to leak micro voltage to ground. Hence why you should not put a Refrigerator on a GFCI.
 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
I have a variable speed lathe that converts to 3phase for the speed control. It trips my GFCI outlet. I have tried 2 different brands, but they both do it. I have "fixed" it by removing the GFCI. While it seems perfectly safe to me, I prefer to do things properly. Any hope here?

IDK if it is using a VFD convert 1 to 3 phase but those can have a high leakage current. Check the specs.
 

kwired

Electron manager
Location
NE Nebraska
As motors get older, they tend to leak micro voltage to ground. Hence why you should not put a Refrigerator on a GFCI.

Fix the fridge, or throw it out and keep the GFCI.

One reason GFCI is required in unfinished basements, garages, outdoors... is because presence of grounded surfaces, not just water like everyone thinks of first. If the EGC in your appliance cord becomes compromised and the metal frame of appliance becomes energized the risk of shock is higher in the areas mentioned in 210.8 than it is in your typical living room or bedroom. Also a reason permanently wired appliances don't need GFCI protection but a cord connected appliance does - their EGC isn't as easily compromised as a cord connected appliance may be.

Removing GFCI protection stops the nuisance of it tripping, it does not stop current leakage onto the EGC, which becomes more of a hazard should that EGC ever become compromised.

Motors don't leak voltage to ground. If insulation is compromised it may leak some current to ground. A motor full of dirt and/or moisture may cause enough leakage to trip GFCI's. I have cleaned up a few and they no longer leaked enough to trip.

Had a spa pump motor one time that had a plumbing leak dripping right onto motor - it kept tripping GFCI. Took motor apart cleaned and dried it out - fixed the plumbing leak, and put it all back together and everything was fine again.
 

tersh

Senior Member
Location
new york
As a GFCI of last resort. Try the Siemens 2-pole GFCI breaker. It has never tripped on my two refrigerators which kept tripping when they were put on the GFCI receptacles (sometimes plugging in cellphone charger can also trip it).

I thought something wrong the fridge. I nearly bought an expensive clamp meter just to trace the leakage. One fridge is 10 years old. The second fridge is new.

When they were put on the Siemens. They never tripped anymore. Not even once.

Also to know if the tripping of the receptacle is caused by real leakage current or something more mysterious like capacitive coupling from inductive kick. Just supply ac power to the load side of the GFCI receptacle. Here the input is opened. If it still tripped, then it's not leakage current. My dozen of GFCI outlets can trip even when ac supply was put at load. LC Filter can eliminate them. All my outlets were protected by GFCI outlets that is also protected by the Siemens GFCI breakers for ultimate protection (although the ultimate would be design that can open up the contacts when there is fault in the circuit but the problem with this is what if the power goes out, you can't have contacts that suddenly opened because then you have to close each one when lights come back, lol)..
 
Status
Not open for further replies.
Top