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Thread: Open Neutral Question

  1. #1
    Join Date
    Feb 2017
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    Titusville, FL
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    99

    Open Neutral Question

    I have a Camaster CNC machine in my shop.

    To hook the machine to power, we used an existing 50 amp RV plug, and ran a 6 guage wire from the machine to the RV plug and it works fine. I can now plug / unplug the unit when it is not in use.

    I live in Florida, and the CNC machine has a lot of electronics including the PC that controls the entire unit. I thought it would be great to add an RV 50amp surge protector on the outlet to protect the unit vs pulling the plug out when I am not using the machine...

    I got the following unit: 50 amp portable Surge Protector for an RV with digital display.
    RVSurgeProtector.png

    The RV wall plug is wired with 2 hot's, ground and a neutral for 220v circuit.
    The CNC machine is wired with 2 hots and a ground. There is no specific spot for a neutral.

    When I plug the surge protector into the RV plug, it reads everything perfect, when I then plug the CNC machine it shuts down stating that I have an "Open Neutral". There is no way to turn this off, it is a safety item on the RV surge protector to prevent open neutrals in an RV. However, the CNC machine does not need a neutral.

    Am I able to use this device with my CNC machine?
    As a test, we ran a neutral wire to ground on the cnc side of the wiring and that did not fool the unit, it still detected an issue with the neutral...

    For now I have the unit disconnected, but would really like to use a surge protector on this line if possible...

    Thanks

  2. #2
    Join Date
    May 2007
    Location
    Don't Mess With My Texas!
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    128
    Your RV and your CNC are two very different animals, electrically speaking. One of them is completely isolated on rubber wheels; electrically like a mobile/manufactured home.

    You are trying to mix the two, and finding out it won't work. That shouldn't have been a surprise.

    I'm not enamored with "surge surpressors", in the same way I'm not enamored with "tooth whitening toothpaste." Lots of claims and advertising.

    Since your area of Florida has so much lightning, spend your money and time on a whole house system (at the input power point) and/or an Uninterruptible Power Supply (UPS) for the electronics part of your CNC, so it will never lose power.
    Paul
    These words are my opinion, WYLION. Any resemblance to truth or fiction is accidental at best.
    "Truth lies dormant in our future history." ― Paul Lawrence LXXI


  3. #3
    Join Date
    Nov 2012
    Location
    North Dana, Masachusetts
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    486
    Lighting is a problem in my area. I live on a rocky ridge, and awe get struck a lot. I have found that the ground wire can be a path to lightning damage. The current comes in on the ground, and has fried my stuff. I installed plugs on everything, instead of wiring it in directly to boxes. This way, everything can be isolated from the ground. This also meets code. The dust collection pipe is insulated by a non conducting sleeve at the exterior wall.

    I also installed a hefty surge protector at the main panel. I have no idea if it works, but time will tell. Using surge protectors in the way they were designed to be used saves money.

  4. #4
    Join Date
    Mar 2003
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    SE PA - Central Bucks County
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    65,685
    Anthony, the specs I worked from for my own Camaster CNC machine required a four wire 240v/120v circuit per the specifications because while the spindle is 240v, the electronics are 120v. There was a spot for all four connections in the junction box on the CNC machine. (hot, hot, neutral and ground...ie, black, red, white and green) It doesn't sound correct that you don't have a spot for the neutral on the machine.

    Last edited by Jim Becker; 11-12-2018 at 9:30 AM.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  5. #5
    Join Date
    Sep 2016
    Location
    Modesto, CA, USA
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    9,882
    A line reactor for the entire shop will do a lot to reduce surges that are beyond a surge suppressors ability. You might even put one on the ground wire if lightening is an issue.
    A line reactor will also protect the house wiring from surges caused by machines shutting down in the shop.
    Bill D.

  6. #6
    Join Date
    Dec 2006
    Location
    Toronto Ontario
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    11,248
    Hi, most 240 volt equipment won't have a neutral.

    If the equipment needs control power other than 240 volts, it will use a built in control transformer for that.

    Your surge suppressor is detecting that there's no neutral on the load, so it won't power up. You need a surge suppressor that doesn't have open neutral detection..........Regards, Rod.

  7. #7
    Join Date
    Mar 2003
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    SE PA - Central Bucks County
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    Rod you are generally correct, but the reason I posted what I did is that "my" Camaster CNC requires dual 240v/120v voltage from the receptacle/source via four wires. Anthony needs to check on that for his specific machine which is larger than mine.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  8. #8
    Join Date
    Dec 2006
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    Toronto Ontario
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    Agreed Jim, that's why I said "most".

    I have never seen a single phase 240 volt machine that required a neutral, doesn't mean that they don't exist, just means that in 40 years I've never seen one......Rod.

  9. #9
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    CNC kinda changes the game, Rod, because these machines have both "motors" and electronic control setups. The big industrial machines seems to be different than the smaller production machines that have become very prevalent these days in this respect, of course. I believe Anthony bought a Cobra or Panther which are two steps and one step above my machine respectively, so there may be some differences. I don't know and don't have the setup guides for them available.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  10. #10
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    Dec 2006
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    Toronto Ontario
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    Thanks Jim, I've only worked on the industrial machines and they all use a control transformer.......Rod.

  11. #11
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    Yea, the mid-range machines like Camaster and others offer are designed to go into the typical small to mid-size shop environment and utilize common components, rather than custom industrial solutions. Camaster, for example, uses WinCNC for machine control as it's very capable and very affordable. While the bigger ones do sometimes need three phase due because of higher electrical requirements for horsepower, it's still approachable by more "normal folks". Camaster, ShopSabre, Laguna and a bunch of others are all "similar" in this respect.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  12. #12
    Join Date
    Sep 2006
    Location
    Deep South
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    My friend has a Woodmaster (I think) drum sander that is driven by a 5 hp, 240VAC motor. It has a 120VAC variable speed motor for the feed belt. It requires a 4 wire 240VAC connection. That is the only 240VAC woodworking equipment I have ever seen that requires a neutral.

    Quote Originally Posted by Rod Sheridan View Post
    Agreed Jim, that's why I said "most".

    I have never seen a single phase 240 volt machine that required a neutral, doesn't mean that they don't exist, just means that in 40 years I've never seen one......Rod.

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