Strange Problem with Sieg SC4 (LMS 3540) and Ground Fault Outlet

[pontiac428]

GFI is part of the electrical code, unfortunately. I'm at the electrical phase of my shop building, and the electrician I hired to do my panel connection is the local community college instructor for electrical code. He taught me a few things while I helped him pull wire about GFI. A GFI breaker is the best way to go, but they cost $70 each, so that's a grand on breakers right there. For $20 per circuit, you can use a standard breaker and run a single heavy duty GFI outlet first in line in series with cheap, regular grounded outlets. It isn't necessary to have a GFI outlet on every receptacle. You can use the money saved ($50 per circuit!) for something else that you actually want in your shop. That may help with the number of senseless GFI trips. For the record, I hate GFI outlets. My Oster beard trimmer tripped the one in my bathroom three times the other day, and that's a 20 watt double-insulated power tool.

 

[MontanaAardvark]

For $20 per circuit, you can use a standard breaker and run a single heavy duty GFI outlet first in line in series with cheap, regular grounded outlets. It isn't necessary to have a GFI outlet on every receptacle.

That's exactly how they wired my shop.

I have other GFI outlets in my house, and a GFI breaker in the breaker box. The one on the west wall of my shop is the only one that goes off randomly. That's why I tried replacing it and ran into this issue with the brand new GFI outlets getting tripped by my lathe, but the old one that was installed in '14 doesn't get tripped.

 

[DavidR8]

These are excellent remarks. I don't know what kind of motor is in the lathe; my guess it's "whatever is cheapest" in China. The manual says "Brushless motor" which implies the controller is varying the frequency applied to the motor and not varying voltage. Probably a cheap PWM controller.

I would double check to see if the motor is truly brushless. My 7x14 was advertised as having a brushless motor but actually has a brushed motor.
I have no idea if a brushed motor would leak voltage to ground.


Sent from my iPhone using Tapatalk

 

[Meta Key]

I wasn't familiar with Sieg machine tools (sounded vaguely European) so I went to the LMS web site to take a look.

3540 lathe at LMS

I was reading about the machine and clicked on the tab for "Chris' Tips" where I read:

"We have no expectation that any HiTorque machine will work on a circuit with a Ground-Fault Circuit Interrupter (GFCI). The National Electric Code has a specific exception to the requirement that receptacles in a garage or work area have GFCI: "Exception No. 2: A single receptacle or a duplex receptacle for two appliances that, in normal use, is not easily moved from one place to another and that is cord-and-plug connected"."

MK

 

[MontanaAardvark]

Thanks for that Meta Key.

I go to the lathe's product pages so often that I think I've memorized them, but obviously not. I think "not easily moved from one place to another" is a good description for a lathe that weighs about 250 pounds on its base cabinet.

The manual doesn't address a GFCI but specifically calls for a grounded outlet, which I have.

Today, I isolated the ground pin with an adapter socket (example) like you would use to plug a 3 pin grounded plug into a 2 pin outlet with a separate ground wire. I could run it up to 250 or 300 RPM and it didn't pop the GFCI, so that indicates the ground is the issue. I have an oscilloscope and could see lots of high frequency noise on the AC line. At the moment, I'm not comfortable enough with that measurement to put a number on it.

I'd rather keep the GFCI for my milling machine because I use water-based coolant on it. I'm still studying.

 

[salindroth]

Maybe this is a problem that I'm the only person in the world has seen but with millions of SIEG lathes out there, maybe someone has seen it.

My big lathe is a Sieg SC4 bought as the Little Machine Shop 3540.

I've been having issues with a ground fault interrupter in my shop popping for a while that are definitely not related to the lathe. The lathe will be off and the GFI will turn off power. The majority of that went away when the electric utility replaced a transformer, but it would still pop open every few weeks or go a couple of months.


Anybody seen something like this?

Bob

Coming late to this thread, but I had the same problem with my LMS lathe and mill. I wrote to LMS and Chris Woods replied that I should not use GFI outlets because "these machines turn your AC into DC, then reassemble it to 3-phase. The phase shift unbalances the hot and neutral."

Scott

 

[middle.road]

Another 2cents which may not even apply to this,
Lived in a sub-division several years ago that was built by a crooked contractor.
All the houses were less than 10 years old at that time.
We kept experiencing weird trips on both conventional and GFCI circuits. Blew out a few computers before I scored some extra UPSes.
To make a long story short the electrical utility came through and pulled all the meters and re-did the lugs and replaced the meters.
One of the neighbors had a small fire inside their meter box and that was what triggered the repairs.
I talked to the supervisor when they were affecting the repairs and he said that all 24+ homes had not been installed properly.

 

[MontanaAardvark]

Coming late to this thread, but I had the same problem with my LMS lathe and mill. I wrote to LMS and Chris Woods replied that I should not use GFI outlets because "these machines turn your AC into DC, then reassemble it to 3-phase. The phase shift unbalances the hot and neutral."

Scott

I've come to the conclusion that was the cause of the problem with my lathe. That and if you look on the Chris' Tips tab for their page on this lathe, it says something like, "we don't expect any of our machines to run on a GFCI" Then they quote a justification from the national electrical code saying the GFI outlet isn't required in a case like this: a big, non-portable machine plugged into the wall. An electrician tells me that has been removed from the code in the 2014 update.

Anyway, I've just moved the plug for the lathe into an outlet that doesn't have a GFCI, just a good ground, which is what the manual calls for.