I’m in the process of wiring my workshop and am hoping to get a little advice on what is needed for the VFD power wires. More specifically rather or not I need to consider shielding the wire from the junction box to the outlet? I have a 2.2 kw 220 spindle which will have a dedicated line which I plan to run about 6 to 8 inches from other electrical wires passing though the same wall. Also, are there other considerations I should know when planning the electrical for the VFD and Spindle? Thanks
When setting up power for a CNC machine, it is a good idea to keep the main parts on their own circuits. The spindle, the controller and stepper motors, and the dust collector should each have their own breaker. This keeps the machine running smoothly and helps cut down on electrical noise that could cause problems.
In most homes in the United States, the electric service is split into two lines, each one going to one side of your circuit breaker box, plus a neutral. Each line to neutral gives 110-120 volts. When you connect both lines together, you get 220-240 volts. To do this, you use a double breaker that ties into both lines (sides) in the panel. Larger shops and factories often use three line service, which is called three phase power, but that is not common in houses.
For a typical home workshop, the spindle usually needs a 220/240 volt circuit of its own. The controller and dust collector should be put on their own 120 volt breakers, ideally on opposite sides of the panel so the load is shared more evenly and to keep interference at bay.
When running wires, trying to keep power cables a few inches away from each other is not a bad thing, but I’m not sure this is as critical as keeping things on separate circuit breakers.
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I have 5 circuits for my cnc area. 4 are currently used.
1 for the dust collector and IoT (which also has the PE), 1 for the power strip (which powers the pumps and compressor), 1 for the UPS which has controller and some of my other low voltage items like my brake and temperature sensors, and 1 220v for the spindle.
All are 12/2 wire, and I added a voltage appropriate switch for the spindle so I can have the vfd semi-out of the way.
4x 110v are wired to their own outlet (not to be confused with receptacle) on their own circuit, so I’m using a 2-gang box there, and the spindle is like I said down below the rest of it with a rocker switch to turn on and off.
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I disagree. The weaving of the hot bus bars doesn’t make a difference if they’re one after another or 1 on the left and 1 on the right. Since there’s only 2 hot bus bars (most likely) vertically is just as acceptable. Regardless, it would share a bar with other 220v appliances such as dryers, air conditioners and (electric) ovens. It wouldn’t be advisable to skip slots resulting in it being on the same hot bus bar, but the load is still 200a (most likely), and while maybe not optimal, it’ll still work (depending on how taxed that bar is at the time of usage). The whole bar for its length is hot, not “its stronger at the top than the bottom”. If your experiencing EMI, your problem more likely than not lies elsewhere
It was much easier for me to go vertically on the left with my 110v (mostly) and 220v (mostly) on the right.
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I agree and misspoke when saying “left” and “right” as far as the breakers themselves as each hot leg is indeed interweaved and alternating between the actual breakers going in a vertical position down each “side” of the panel. I was referring more to the left and right hot wires themselves, as the incoming mains (at least all the boxes I’ve seen) are terminated at the top of the panel in a left-right orientation.
Regarding EMI, I was speaking from my first-hand experiences. When I got my 1F I did the classic Makita brushed router. After running this thing for many hours, the brushes started wearing down and arcing which caused the steppers to skip and the controller screen to blank out. As a diagnostic step, and before the replacement brushes arrived, I moved the router to a separate circuit on the other hot leg and the issue stopped. Was there still EMI being produced by the router? Absolutely. But what I did was recommended by others on the 1F forum at the time and it actually worked. At least enough that my motors stopped missing steps. Would these missed steps return if I kept going without replacing the brushes? Almost certainly from what I just learned.
Thanks to this discussion I now went further down this rabbit hole of knowledge about EMI specifically. It appears that EMI can pollute the other hot leg(s), even if the pollution maker was on a 120v circuit, and not only a 240v that spans both legs. This is because of the shared neutral/ground situation. And this even holds true in an un-bonded (separated) neutral/ground scenario of a sub-panel which I found very insightful.
Takeaways for me include:
To prevent EMI:
- Use good quality shielded cables. Thanks to PwnCNC, we got this is covered!
2. Use line EMI/RFI filters at the panel or device. I can’t remember if the PwnCNC VFD has a filter, but something to keep in mind.
3. Use a UPS (or isolation transformer) for the CNC controller to have even more isolation but only a few UPS models offer true EMI protection such as ones from Tripp Lite or CyberPower
4. Ground all equipment as best that you can
To prevent voltage sags:
Use separate hot legs. But this may only come into play if your main panel is say 100 amps (my old house) and you are trying to run the HVAC and/or a couple space heaters, along with other large-load appliances at the same time you want to run a 240v spindle and dust collector. A 200 amp service along with mindful attention to what the rest of your current draw happens to be “should” not cause any issues.
Main panel, same. My wife 100a sub on the other hand has a breaker on both ends.
Your anecdote here made me recall my own experience where when the AC kicked on, my z would drop about 1/16” - 1/8” on my shapeoko 3 with hdz. It was Daniel’s recommendation that I get a UPS and have the machine on it, that the problem was solved. Although that’s a brownout… not emi
It does
Thanks for all the good information. For a little clarification the workshop has independent 400 amp service, with single phase 220 v. The shops dust collector is housed in a utility room off the side if the building with the air compressor. Both of these are on independent 220 v lines. Right now I have one 110v line from the junction box to the cnc area which runs 6 inches above other shop electrical lines. There are 2 other junction boxes each on their own circuits for the chiller and miscellaneous electrical needs. Finally, the VFD and Spindle have their own dedicated 220v line from the junction box, this runs 6 inches above the CNC main line. Right now I’m mostly trying to determine if this line should be put in a tinned copper shield or if that isn’t needed. Everything else in the shop that runs on 220 is either on the far wall or runs down the center of the floor, in the case of the cabinet saw. Thanks again for any information.
In the wall? No.
Outside of the wall? Should have metal conduit fittings, haven’t seen copper though.