# GFCI vs Variable speed



## Skewer (Oct 22, 2016)

All the outlets in my garage are GFCI, and my lathe pretty frequently trips the circuit when i turn the speed up.

I'm curious to know if anyone knows how i can get around this (staying within code), other than running an extension cord in the house.  I've done some 'googling' and i see some mentions of filters(?) or more expensive GFCI circuits - but no definite solution.


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## JimB (Oct 22, 2016)

What lathe do you have and are there other things plugged into the same circuit. It doesn't need to be the same outlet as there can be other outlets connected to the GFIC outlet


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## Skewer (Oct 22, 2016)

Its a delta 46-460 (120v).  I'm pretty sure the whole garage is on that circuit but i usually don't have anything else on other than a 4 foot fluorescent light.


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## frank123 (Oct 22, 2016)

You sure the GFCI is good?  

And all the wiring and connections tight and installed right at every connection and the breakers OK?


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## Skewer (Oct 22, 2016)

I found mention that someone fixed their issue with a 'hospital grade' GFCI outlet.


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## Skewer (Oct 22, 2016)

I can only assume so - I moved this year and had the same issue at the old place.  I just thought it was a known issue between GFCI and variable speed lathes.



frank123 said:


> You sure the GFCI is good?
> 
> And all the wiring and connections tight and installed right at every connection and the breakers OK?


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## tomas (Oct 22, 2016)

What is the amperage on your circuit?  I use all 20 amp circuits in my shop and have never tripped a breaker or a GFCI.

Tomas


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## qquake (Oct 22, 2016)

My Jet 1221VS is plugged into a GFCI, and it never pops.


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## Skewer (Oct 22, 2016)

15 amp.  To be a little more clear the breaker doesn't trip but the GFCI circuit does.  This is an older model of the 46-460 lathe (type 1).



tomas said:


> What is the amperage on your circuit?  I use all 20 amp circuits in my shop and have never tripped a breaker or a GFCI.
> 
> Tomas


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## jttheclockman (Oct 22, 2016)

Skewer said:


> All the outlets in my garage are GFCI, and my lathe pretty frequently trips the circuit when i turn the speed up.
> 
> I'm curious to know if anyone knows how i can get around this (staying within code), other than running an extension cord in the house.  I've done some 'googling' and i see some mentions of filters(?) or more expensive GFCI circuits - but no definite solution.




"Frequency harmonics"  First of all when you say all. Is there one gfci and all other outlets are normal outlets???  What else is on the circuit??  What type of fluorescent light is it??  How old is the GFCI?? What kind of lathe and how old. I ask these questions because the older GFCI use to trip any type motor that has a frequency shift. Without getting too technical If that is an older flourescent light that too has a ballast that is frequency driven. Catch the right part of any cylce (60 cycles) and it will trip the GFCI. This was a huge problem years ago with refrigerators tripping and that is why the code allowed them to be unprotected  (many people had older fridges in garages for extra storage) As long as they are plugged into an outlet that has only one outlet it does not have to be gfi. 

Quick answer without all the facts. Change the GFCI because they have been updated and unless you buy an older one laying on the shelf from some hardware store. Try changing the light or shut the light off and see if the lathe still trips it. If not change to an incandescent light. LEds can cause a problem also.


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## tomas (Oct 23, 2016)

Skewer said:


> 15 amp.  To be a little more clear the breaker doesn't trip but the GFCI circuit does.  This is an older model of the 46-460 lathe (type 1).
> 
> 
> 
> ...



Is your lathe properly grounded?  The purpose of the GFCI is to protect you from ungrounded equipment.  If the lathe is properly grounded, I would try a different GFCI.

Good luck!
Tomas


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## Skewer (Oct 23, 2016)

There are four outlets in the garage - one is the gfci circuit.  When it trips, the other three go out with it.  I unplugged the light over the lathe (it was plugged into the same outlet as the lathe) and ran it for a bit, and after a while it kicked out again.  The house is new, and finished construction this year.

I shut off the breaker in the garage and the overhead lights also went out.  I'm not sure how to answer as to what 'type' the lights are - all three here are 2x bulb four foot fluorescent tubes.  I'll open up the garage today and cut the overhead lights off and run the lathe and see if that does anything different.



jttheclockman said:


> Skewer said:
> 
> 
> > All the outlets in my garage are GFCI, and my lathe pretty frequently trips the circuit when i turn the speed up.
> ...


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## jttheclockman (Oct 23, 2016)

What is the amperage of the breaker and is there anything else on that circuit??  Have you used this lathe before and was it plugged into a GFCI before?? Is there another gfci near the garage like in the kitchen over the counters??  If you could run a extension chord from one of them to the lathe and see if it trips that gfci also. 

Being a newer home they would have used newer equipment such as electronic ballasts in the lights and they are all now filtered. The GFCI could be a low grade but should now have been filtered also. You may want to try a hospital grade GFCI but they will be expensive. Or you may have a fault with the lathe.
My money is still on Frequency harmonics and if the lathe is an older one they did not filter for this. The newer models are now filtered. You can try in a non gfci outlet and I bet it will run fine unless you have a leak to ground then it will trip the breaker.


I just went back and read some of your replys to others and you answered some of my latest questions such as doing this before. The big answer you gave was older model lathe and I am betting that is the problem. They did not filter this problem and it was a problem with many older VS lathes. As I said the best shot then is to upgrade the GFCI and a hospital grade one will do this. They are better at handling nuisance trips. Get at an electrical supply house. If that does not do it then you will need to plug into a non gfci. If you have a garage door opener they are usually not GFCI just because of what I mentioned with frequency problems.


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## Culprit (Oct 23, 2016)

Check the national electric code and don't trust my memory, but dedicated outlets in garages are exempt from being GFCI.   If your circuit breaker box is in the garage, it would be cheap and easy to add a breaker and run a single, dedicated, non-GFCI outlet for the lathe.

I don't have any experience with hospital grade GFCI breakers/outlets so one of them might be cheaper than running a dedicated outlet, but a dedicated outlet will relieve you of the GFCI requirement all together if that's what you want.


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## PapaTim (Oct 23, 2016)

Skewer said:


> I can only assume so - I moved this year and had the same issue at the old place.  I just thought it was a known issue between GFCI and variable speed lathes.
> 
> 
> 
> ...


 
This tells me your lathe likely has a type of short causing a minor bleed to ground. Unplug the lathe, access the internal wiring and make sure all the connections are good and tight.

Try to notice if the problem occurs with any consistency such as after running a certain amount of time or when turning something heavy, or at specific speeds.


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## TimS124 (Oct 23, 2016)

Culprit said:


> Check the national electric code and don't trust my memory, but dedicated outlets in garages are exempt from being GFCI.   If your circuit breaker box is in the garage, it would be cheap and easy to add a breaker and run a single, dedicated, non-GFCI outlet for the lathe.
> 
> I don't have any experience with hospital grade GFCI breakers/outlets so one of them might be cheaper than running a dedicated outlet, but a dedicated outlet will relieve you of the GFCI requirement all together if that's what you want.



I built an "accessory structure" (small shop) in my back yard in California about a decade or so ago...and the inspector insisted that it fell under the same rules as garages and had to have GFCI outlets.  His reasoning was that I might plug in an extension cord to run yard tools...same as with a garage.  

Sounds like one of those rules that varies from place to place...with some places being much stricter.


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## TimS124 (Oct 23, 2016)

Skewer said:


> There are four outlets in the garage - one is the gfci circuit.  When it trips, the other three go out with it.  I unplugged the light over the lathe (it was plugged into the same outlet as the lathe) and ran it for a bit, and after a while it kicked out again.  The house is new, and finished construction this year.
> 
> I shut off the breaker in the garage and the overhead lights also went out.  I'm not sure how to answer as to what 'type' the lights are - all three here are 2x bulb four foot fluorescent tubes.  I'll open up the garage today and cut the overhead lights off and run the lathe and see if that does anything different.



If unplugging the lights helps, perhaps replacing those with LED equivalents would solve your problem.  Lowes, Home Depot, Sam's/Costco, etc should have LED fixtures that resemble traditional 2-bulb 4ft fluorescent fixtures.  Usually under $50/each and they give much better light (in my opinion).

I would've expected local code to require separate circuit for the garage lights...disappointed they're sharing a breaker! Can you get a breaker added and have the lights moved to it?  Suddenly being in the dark when a tool trips its breaker is a safety hazard.

Hope you're able to get it sorted out quickly.


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## Culprit (Oct 24, 2016)

Culprit said:


> Check the national electric code and don't trust my memory, but dedicated outlets in garages are exempt from being GFCI.   If your circuit breaker box is in the garage, it would be cheap and easy to add a breaker and run a single, dedicated, non-GFCI outlet for the lathe.
> 
> I don't have any experience with hospital grade GFCI breakers/outlets so one of them might be cheaper than running a dedicated outlet, but a dedicated outlet will relieve you of the GFCI requirement all together if that's what you want.



I just checked the 2014 NEC (most current one I have) and they removed the GFCI exemption for dedicated outlets in garages.


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## farmer (Oct 24, 2016)

*Lathes*



Skewer said:


> All the outlets in my garage are GFCI, and my lathe pretty frequently trips the circuit when i turn the speed up.
> 
> I'm curious to know if anyone knows how i can get around this (staying within code), other than running an extension cord in the house.  I've done some 'googling' and i see some mentions of filters(?) or more expensive GFCI circuits - but no definite solution.




You could have a weak breaker......
I am running my whole garage off one 15 amp breaker ,  3 variable speed lathes .

I just haven't figured out how to operate all three at the same time :biggrin:
Two of my lathes are set up with live cutters and dust removal system .


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## wouldentu2? (Oct 24, 2016)

Test it off a GFCI from the house and if it does not trip it replace the GFCI. There is a 20 year or so recommendation to replace GFCI's. I had an old one that tripped once in a while I replaced it and never had a problem after that.


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## monophoto (Oct 24, 2016)

Skewer said:


> All the outlets in my garage are GFCI, and my lathe pretty frequently trips the circuit when i turn the speed up.



GFCIs are a good thing to have in a shop - there are many electrical hazards, and GFCIs are are specifically designed to protect people against electric shock.  That's why the NEC requires them on receptacle circuits.  However, there several things that can trigger GFCIs.  And more importantly, the 'problem' may actually be a symptom of something else.

Potential issues include:


harmonics - electronic devices on the circuit cause voltage harmonics, which in turn cause current harmonics to flow in the circuit. GFCIs, like all other electrical devices, are designed for the fundamental frequency (60Hz).  In some cases, it is possible to predict what harmonics might be present (for example, a simple three-phase variable speed drive device will produce a significant 300 Hz component, but a single-phase variable speed device will produce other frequencies including a significant third harmonic (180Hz).  And depending on the design of the variable speed controller  on the lathe, the harmonic composition of the current to the lathe can  change as you change speed.  In this instance, the circuit feeds both the variable-speed lathe as well as fluorescent lights, both of which are known sources of harmonics.  Conventional magnetic ballasts produced third-harmonics, while modern electronic ballasts produce other frequencies.  The GFCI designer can't possibly know what harmonic frequencies will be  present, so in general, the high-frequency response of the detection circuit in consumer-grade GFCIs  is unknown.


Neutral-to-earth circuit - in theory, all of the current that flows out the hot lead (the black wire) should return via the neutral (the white wire), and the main protection functionality in a GFCI compares these two currents - if they are the same, everything is fine.  If they are not the same, that could be because a person has come in contact with the hot wire and current is flowing through that person's body.  In that case, the GFCI is designed to trigger.   Inadvertently grounding the white wire at the load can also upset this balance, so some GFCIs are designed to detect when the neutral is grounded  They do this by impressing a high-frequency voltage between neutral and ground and looking for a corresponding high frequency current flow.  But that high-frequency current detection circuit can be fooled by high frequency currents that flow in the circuit for other reasons.


excessive leakage.  Every circuit includes some unavoidable leakage - both resistive leakage through insulation, and capacitive leakage because the circuit parallel the earth.  If that leakage is excessive, it can appear as an undesirable unbalance between the hot and neutral currents.   The leakage increases with circuit length.  This was a common problem with early GFCIs that were installed in the service panel. The current practice of putting GFCIs in the receptacle itself means that the circuit length beyond the GFCI can be shorter, thereby reducing the tendency for this problem to appear.  But if there is too much circuit beyond the GFCI, it can still trigger incorrectly.


a combination of these factors

Are the lights in the garage hard-wired or plugged into a receptacle? The NEC requires that there be a GFCI on receptacles, but not on hard-wired fixtures.  I would consider modifying the wiring to make then hard wired (ie, NOT connected through a receptacle), and then connect them to the circuit ahead of the GFCI. 

Also, I would bring the main feed in to the garage from the house, and then split it into three branches.  One branch would feed the hard-wired lights.  The second would feed general purpose receptacles though a GFCI, including any receptacles outside the garage.  The third branch would feed a single receptacle for the lathe through a dedicated GFCI.  That way, any harmonic currents caused by the lathe would affect only the one GFCI associated with the lathe.

If the problem persists after these modifications, then it is likely that the cause is the lathe itself - either simply a high variable magnitude harmonic current, or a high leakage current combined with a variable magnitude harmonic such that the combination is triggering the GFCI.  You could always hard-wire the lathe (eliminate the receptacle) in order to get around the NEC requirement for the GFCI, but that would mask the fact that something is happening in the lathe that could be an incipient problem in the variable-speed box.


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## Culprit (Oct 24, 2016)

I looked up the two main brands of GFCI outlets sold here in my part of Virginia: Leviton and Cooper.  All GFCI outlets in the US should be tested to UL 943.   Hospital grade GFCI outlets are also tested to UL 498.   

Leviton also goes the extra step and tests their non-hospital grade GFCI outlets to UL 498 as well (at least their current Smartlock Pro self testing product line).   I can not find any evidence that Cooper builds their residential GFCI outlets to meet UL 498.

I suspect that it is cheaper for Leviton to just make all their GFCI outlets one hospital-grade configuration and market them in different packaging than to actually tool up and produce a lesser grade for residential use.  Just a guess.

The Leviton product sheet for their residential and hospital grade GFCI outlets (those tested to UL 498) says "improved immunity to high frequency noise reduces nuisance tripping."  I can find no such claims in literature for Cooper brand GFCI outlets.  

The bottom line is that I'll bet your current GFCI outlet is not a Leviton Smartlock Pro.   And if you are going to replace the outlet, you don't need to pay extra for a hospital grade version - just find one that is tested to the hospital grade UL 498 - i. e. a Leviton Smartlock Pro.  There may be other brands available, but that is what I find to be the most readily available.

I haven't personally tried it, but some guys online have reported success using ferrite beads on the end of the power cord.  One guy even claimed that tying a few overhand knots in the power cord provided enough disruption to filter out the high frequency noise and eliminate his GFCI nuisance tripping. Your mileage may vary.


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## jttheclockman (Oct 24, 2016)

The code has changed. It used to be you were allowed a non gfi outlet for overhead garage door opener, any freezer or fridge in the garage as long as it was a single outlet and not a duplex. But that changed because people would get rid of appliances and the outlet is still there. Any outlet in a garage could be used with an extension chord to out side so they changed the code. 

A better grade GFCI should solve the problem. I always liked Pass and Seymore 

or Hubble. Leviton are construction grade outlets and switches. 

It is your shop so if you want to take that gfci out and replace with a normal outlet and move the gfci to the next outlet in the row, only you will know. You are still protected by overcurrent  protection from the breaker. Did not hear it from me though.


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## TonyL (Oct 24, 2016)

Thanks JT...I was wondering if there was a make better than Leviton.


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## tomas (Oct 27, 2016)

Skewer said:


> There are four outlets in the garage - one is the gfci circuit.  When it trips, the other three go out with it.  I unplugged the light over the lathe (it was plugged into the same outlet as the lathe) and ran it for a bit, and after a while it kicked out again.  The house is new, and finished construction this year.
> 
> I shut off the breaker in the garage and the overhead lights also went out.  I'm not sure how to answer as to what 'type' the lights are - all three here are 2x bulb four foot fluorescent tubes.  I'll open up the garage today and cut the overhead lights off and run the lathe and see if that does anything different.
> 
> ...



The GFCI is placed on the first outlet in the circuit so that it protects the "down-stream" outlets, as well.  That's why the other outlets go off when the GFCI trips.  Does the plug on your lathe have all three prongs?  If the rounded one is broken off, your lathe is not grounded.  Check where the power cord attaches to the lathe and verify that the green wire is securely attached to bare metal.


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## Skewer (Oct 28, 2016)

I messed with the lights on Sunday and was still having the issue and ordered a 'Leviton N7599-HGI Hospital Grade' outlet from amazon.  The box is also labeled as 'Smartlock Pro' as you guys mentioned.  I swapped it out and haven't been able to replicate the issue.  So far, so good....Thank you guys for your help.


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## donstephan (Oct 29, 2016)

Didn't see any mention in all the prior posts of checking with the manufacturer of the lathe.

If the garage is attached, it is possible there is a breaker box in the house with a single 120V circuit, either 15 or 20 amp, running from the breaker box to service all electrical in the garage.

If the problem reappears, and the lathe manufacturer has no solutions, I'd suggest contacting an experienced electrician.


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