16" South bend saga continues

Thanks to all those who responded to my earlier posts regarding my South bend 16 lathe. Your steering me in the right direction and I really
appreciate it.
I did get a Teco VFD from Dealers Electric. They were very knowledgeable with the wiring of my 3 phase motor. I'd recommend them to anyone too!
I hooked it up today and it worked just as promised. The motor is not in the lathe but on my bench. I wired it just to make sure everything worked right. I love the variable speed control you get with the VFD.
The manual recommends a ground going directly to earth from the VFD. This is to avoid radio interference. I'm a bit uncomfortable doing that. I was always under the impression that you should only have one ground from your main panel. That's why all my subpanels are not grounded individually but are grounded back to the main. Any thoughts on this?
Also, I need to wire my garage now for 220V. Can anyone tell me if 12 gauge wire with a 20AMP breaker is adequate for this setup or should I go to 10 Gauge with a 30 Amp breaker? I am leaning towards the 20 Amp setup.
Motor is a GE 3HP 3 Phase 460V 1800 RPM and is wired through the Teco which is running on 220 Volts.
Thanks in advance for the help.
Ted
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Ted wrote:

The ground and neutral are not to be bonded in a subpanel, but that has nothing to do with additional ground points. You can add additional grounds where appropriate as in the RF noise suppression recommended for the VFD. The one thing you should do is test of objectionable ground loop currents at the new ground, which can be done with a clamp on amp probe.
Pete C.
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The Teco puts out 460 V? wow.... I woulda thought you'd rewire the motor down to 220.
Earth ground is not the best ground. Usually the cold water main is. Much better than the gas or sewer main. In my area, the cold water pipe is better than the neutral supplied by the goddamm utility. Different ground points can cause ground loops, or hum, according to some sound guys. See what happens. Proly not a problem just for power stuff.
I would think you'd have a whole subpanel for your garage. Is your garage your shop? No such thing as too many amps or too thick a wire, or too many circuits. Even 10 ga/30 amps seems low. 20 A will do you for the VFD, lights, and a drill press or two, but what about other stuff? -- Mr. P.V.'d formerly Droll Troll

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FYI... your VFD torque curves may not be set for the optimium condition when you reinstall the motor on the lathe.
You will have a LOT more "drag" on the motor when actually turning a spindle and a chuck.
Most VFD have multple, pre-programmed torque/HP curves if you don't select the right one,
The "general" or factory setting will usually work, OK -- ie get you started, but you may find that you can stall the motor very easily with any kind of turning cut .. Alternatively, if you have a geared head lathe, you will need more startup ""boost" to overcome the inertial of gears and the weight of the chuck.
you should experiment to find which is the best one for YOUR lathe set up. easy to do.. takes all of 5 seconds to change the "Volt/HZ" parameter...
Steve

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Don't know for sure about the VFD ground - you can call the local electrical building inspector and ask and get a good answer.
Search on "voltage drop calculator" and do the calculations for your setup. Code says to keep voltage drop below 5%, my electrician friend and I like 3% (mainly because I don't like the sound of a struggling motor when I plug in something a little bigger than planned). I've got 6 AWG running on several circuits.
Steve.
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I wired our barn *twice*, redigging the wire ditch between the buildings in between. I remember my logic--why would I ever need more than 20A at 220V in the barn? Then I found out about electric welders.
Trust me, put in the larger service. You'll end up using it for something.
Steve Smith
Ted wrote:

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I'm to the point where I put conduit in for both power feeds and data cables. It seems that my ability to anticiapte future needs is woefull. And I recently switched from 1/2" ENT conduit on the data cables to 3/4"
Steve Smith wrote:

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I guess I wasn't clear about wiring my garage for 20Amps when I wrote this last night.
What I meant was I will be wiring "in" the garage for another circuit that will be running 220V. The whole garage is "wired" with a 100 Amp service sub panel. It is not bonded or ground to earth but back to the main panel at the house.
I like to wire each machine on its own circuit.

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I just did this myself about a week ago "the wiring part that is" I believe we went with 12 or 14gauge and its piggy backed onto the house line to a 30amp breaker since the box in the garage isnt made for 220. Did it for my new enco lathe works good.
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I hope you have some numbers wrong. 12ga is good for 20A and 14ga is good for 15A. If either of those is on a 30a breaker it's an invitation to disaster.
--

Clif


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maybe we did end up with 10 then hrm dont recal I know it was rated 30amp because we were looking specifically for that, know we had talked about getting 12 or 10 and possibly 14.
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Nope I was right we used 12gauge but I thought it was 30amp rated, don't have the box anymore so can't say for certain however my lathe only takes 10amp's so there shouldent be any problem I wouldent think. And the lathe is the only thing that wire is ever going to be used for. Its just run across the cealing and hanging for the lathe to plug into. And I will remove it if we ever sell the house/garage. We did use 30amp plugs I know that almost for certain.
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