Older lathe vs GFCI

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monophoto

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Mar 13, 2010
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Saratoga Springs, NY
This issue has been discussed at length. The answer is maybe.

If the lathe uses some form of electronic variable speed control, it is possible for there to be an interaction between the speed control and the GFCI that can cause tripping. This is not a problem in the sense that something is wrong - its just a consequence of the technology. There are so-called 'hospital grade' GFCIs that reportedly are less likely to be a problem in this situation than ordinary residential GFCIs.

If the lathe uses mechanical speed control (either pulleys and a belt, or a Reeves drive), it is less likely, but still possible. In this case, however, the fact that the GFCI is tripping could be telling you that there is a problem in the lathe motor or in the GFCI. In some cases, the cause may simply be that the length of the wiring on the load side of the GFCI is excessive.

I know this is vague, but much more information is needed to give a more definitive answer.
 

cjester

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Illinois
Probably. I know mine trips when changing the speed.

The GFCI trips when there's a large enough difference between the current going to the lathe and the current returning from the lathe. Any difference looks like a short and trips the interrupt. If the motor causes a dip or spike when starting or stopping it's going to trip.
 

Dalecamino

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Not sure how much info you need. Let's see... I built the shed 5 years ago. Buried outdoor grade wire from the bottom outlet on the patio to the shed. Been using it with no problems, until I bought a new space heater. 1500 watt. Used it for awhile (hours) It was plugged into a GFCI in the shed. I noticed, when turning it off, THAT GFCI would trip. Finally, the last time, was the last time I had power in the shed. When it started warming up outside, I started replacing everything on that line, which included the two vanity outlets in the bathrooms, breakers and a GFCI in the garage. No good! I finally found an electrician to look at it. He checks the breaker, bathrooms and goes to the patio outlet, checks power. There is power to the patio. So he takes that outlet apart (wires) and rewired it, telling me I was on the right track. 5 years ago!!

So anyway... power is restored to the shed and both bathroom outlets. All is good! Yesterday, I went out to make some pens. Turn on one overhead shop light, one lamp over the lathe, and start turning on the lathe. Turning it on and off numerous times of course. Eventually power went off same as before. I sent the electrician, and asked if there was anything about that patio outlet that needed replaced? He is out of town and will contact me when he returns. In the meantime, I'm thinking...what is overloading this line? There IS an older small refrigerator in the garage. I have unplugged it, since there was only one can of Yuengling in it. I'll take care of that later.:biggrin: The frig could be a contributor to my problem.

Meanwhile...about the lathe. It is a Turncrafter ProVS from PSI, bought in 2006 I did replace the switch last year sometime. Also a belt. No other issues with the lathe. It's been a good one. But I'm wondering, if other issues are now beginning to surface?

I remembered this discussion about the lathes tripping GFCIs in the past, but I didn't follow it. Now here I am asking about it. Thanks for the replies, and I am now waiting for the electrician to find his way back. :wink:
 

jttheclockman

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What I can tell you is that circuit is overloaded and not a proper install just due to the length of that circuit. Is that a 15amp or 20 amp outlet??> Second all motors can trip GFCIs due to frequency changes. Won't go into that. Compressors from refrigs and coolers are known for this and that is why it is recommended to not put them on a gfci.

What I suggest is you take the shed off the GFCI circuit and place it on the hot side of the wiring. You then can change the outlet in the shed to a gfci if you so choose to but use an upgraded outlet some people call them hospital grade. Did not follow your circuitry well. If you are saying you have more than one gfci on the same circuit what side are you tieing into?? One gfci outlet should not trip others if you are tied into hot side or supply side of wiring. If tied in series one will trip the other. Your shop lites should not be tied onto gfci. You are again dealing with frequency changes. That was a big heater to go along with tools running at the same time, plus distance those wires are running and if you had appliances or someone using the bathroom outlets with hair dryer or anything would have put a huge strain on the ampacity of that circuit. If i am following you all were on the same circuit.
 
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Dalecamino

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Thanks John. We're getting there. I think the best solution is a dedicated line to the shed. I'll talk to the guy about doing that. But I've used it the way it is for 5 years.
 

jttheclockman

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Thanks John. We're getting there. I think the best solution is a dedicated line to the shed. I'll talk to the guy about doing that. But I've used it the way it is for 5 years.

A separate feed would be the proper thing to do. You were actually lucky if that has worked well for 5 years but with that heater you were pressing the limits. Especially as I said if all are on the same circuit.
 

Charlie_W

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Definitely agree on a separate dedicated 20A to the shop for tools. I'm guessing your existing circuit is only 15A since it had the bathrooms, patio and garage on it. That is how our neighborhood houses are wired here....too wimpy for everything....Christmas lights and hair dryer tripped the breaker.

You might want to keep the lights on the existing circuit since you have it there, then if you trip your tool circuit, you still have light...and the lights will not put much load on the circuit.
 

MRDucks2

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Dalecamino

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Agree with the separate line. There is a good chance the GFCI in/for the shed has degraded over time, also, especially if has had a lot of load on it over the years.





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Thanks! That was one reason I replaced it two weeks ago. :biggrin:



Hmmm, did we already have this conversation?


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I don't think we did. Might have been someone else. The electrician will be here tomorrow. I was just curious about my original question about the lathe. Got answers! Thanks!!
 

Dalecamino

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It was the lathe. I ordered a motor and control box. Already have new bearings. So some rebuilding, and should be good to go.
 
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