Help with a bad ground


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    Default Help with a bad ground

    I hope this is a good place for this question. I have searched and not found a specific answer.

    I am having disconnect issues with my Shapeoko 3. It does everything that I want and need right now except it disconnects unexpectedly while running. After lots of emails to their support (they have been very helpful) it has been determined that I have a wiring issue in my house. This hypothesis is supported when I shut off all of the breakers except the one going to my shop the machine runs fine with no disconnects. I am fine with running it this way but the rest of my family complains.

    What I believe to be the issue is that the house and wiring are old and have had lots of repairs and additions through their life. During this many of the common and ground wires have been joined at different points in the system. I know this is not good and I should fix it but realistically it will be a while before I am able to.

    My question is: is there a way to add a ground to my shop that I can use for just the CNC?

    I have been told by several people to just add a ground rod and ground everything close to the machine. I can do this but I have also been warned that this can cause a dangerous potential when using two separate ground on one system.

    Any ideas are welcome.

    Thank, Matt

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    Default Re: Help with a bad ground

    Quote Originally Posted by BlackMaddie View Post
    I hope this is a good place for this question. I have searched and not found a specific answer.

    I am having disconnect issues with my Shapeoko 3. It does everything that I want and need right now except it disconnects unexpectedly while running. After lots of emails to their support (they have been very helpful) it has been determined that I have a wiring issue in my house. This hypothesis is supported when I shut off all of the breakers except the one going to my shop the machine runs fine with no disconnects. I am fine with running it this way but the rest of my family complains.

    What I believe to be the issue is that the house and wiring are old and have had lots of repairs and additions through their life. During this many of the common and ground wires have been joined at different points in the system. I know this is not good and I should fix it but realistically it will be a while before I am able to.

    My question is: is there a way to add a ground to my shop that I can use for just the CNC?

    I have been told by several people to just add a ground rod and ground everything close to the machine. I can do this but I have also been warned that this can cause a dangerous potential when using two separate ground on one system.

    Any ideas are welcome.

    Thank, Matt
    Who ever told you it is Dangerous, is correct, who ever told you to just add another Ground rod, don't listen to there advice again, as it is Dangerous ,you can not just add a Ground rod, if you did add a Ground Rod it has to be bonded to the main Ground rod this is the only safe way to add another Ground Rod, this could be more expensive to do than fixing your house wiring, as the Bonding copper wire has be sized for the job

    You are most likely better to run a new line direct from the main Panel to your Garage

    Mactec54


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    Default Re: Help with a bad ground

    Quote Originally Posted by BlackMaddie View Post
    I hope this is a good place for this question. I have searched and not found a specific answer.

    I am having disconnect issues with my Shapeoko 3. It does everything that I want and need right now except it disconnects unexpectedly while running. After lots of emails to their support (they have been very helpful) it has been determined that I have a wiring issue in my house. This hypothesis is supported when I shut off all of the breakers except the one going to my shop the machine runs fine with no disconnects. I am fine with running it this way but the rest of my family complains.

    What I believe to be the issue is that the house and wiring are old and have had lots of repairs and additions through their life. During this many of the common and ground wires have been joined at different points in the system. I know this is not good and I should fix it but realistically it will be a while before I am able to.

    My question is: is there a way to add a ground to my shop that I can use for just the CNC?

    I have been told by several people to just add a ground rod and ground everything close to the machine. I can do this but I have also been warned that this can cause a dangerous potential when using two separate ground on one system.

    Any ideas are welcome.

    Thank, Matt
    Here is a good PDF on the subject of Grounding Bonding

    Attached Files Attached Files
    Mactec54


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    Default Re: Help with a bad ground

    Thanks Mactec54, I went through the pdf. I understand why the equipment room for the MRI at work is set up the way it is. The grid on the ground looks like a faradays cage of sorts designed to route the stray noise into the ground.

    Will your suggestion of running a new line from my main panel to my garage bypass all of the noise on the ground in the rest of the house?

    Thanks, Matt.



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    Default Re: Help with a bad ground

    Quote Originally Posted by BlackMaddie View Post
    Thanks Mactec54, I went through the pdf. I understand why the equipment room for the MRI at work is set up the way it is. The grid on the ground looks like a faradays cage of sorts designed to route the stray noise into the ground.

    Will your suggestion of running a new line from my main panel to my garage bypass all of the noise on the ground in the rest of the house?

    Thanks, Matt.
    Now you did not say that noise was your problem, running a new independent supply will help, but you have other problems if you have noise interference in the house

    Lets start with your spindle what do you have for a spindle and is it run with a VFD Drive, or is it something else

    Mactec54


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    Default Re: Help with a bad ground

    I may have misspoke when I said noise. When I was talking about my ground from the house I ment errant current occasionally sent to the ground because of either a failing appliance or the mixing of neutral and ground wires. I do have a chinese 1.5k spindle with a VFD. I wired it all according to the best information I could find. When talking about the spindle I ment noise as a current induced in a wire from the VFD or spindle. I was using them interchangeably because in my mind they are just unwanted current in my system. All of this is at the limit of my electrical knowledge and I am sure that I am getting things wrong.

    The good news is that I ran a new line from the subpanel in my garage that I use for my welder. The subpanel goes straight to the main panel and I can see it is wired correctly. I used a new breaker and ran the line to my shop from the subpanel and am only running the CNC on it. Without the spindle running the CNC did not disconnect at all during about two hours of running. Normally without the spindle running it would disconnect after about 3-10 minutes. Two hours is longer than it could do before so I think the new line eliminated/bypassed what ever was causing the problem. Unfortunately when I started the spindle it started disconnecting again and I tried the latest suggestion from the Shapeoko tech support which was run a ground wire directly from the spindle frame to a ground prong on my outlet. Doing this has allowed me to run the CNC with the spindle running for about 1-1/2 hrs with no disconnects. I will be testing it more tomorrow. I have gotten my hopes up before.

    In summary I think I had two problems...the bad power/ground from my house and bad grounding/noise from the spindle. That is why the CNC would run fine if I turned off all of the breakers in the house except the shop but would still disconnect when I ran it with the spindle and also why it would disconnect even when the spindle wasnt running and there were other breakers on in the house. It seems like it would have been easier to see now that I know what was happening (or think I know) but hindsight is 20/20.

    Thanks for you suggestion of running the new line. It was the breakthrough that I needed to get this far.

    Also, thanks for your time in answering and being willing to help. Matt.



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    Default Re: Help with a bad ground

    Quote Originally Posted by BlackMaddie View Post
    I may have misspoke when I said noise. When I was talking about my ground from the house I ment errant current occasionally sent to the ground because of either a failing appliance or the mixing of neutral and ground wires. I do have a chinese 1.5k spindle with a VFD. I wired it all according to the best information I could find. When talking about the spindle I ment noise as a current induced in a wire from the VFD or spindle. I was using them interchangeably because in my mind they are just unwanted current in my system. All of this is at the limit of my electrical knowledge and I am sure that I am getting things wrong.

    The good news is that I ran a new line from the subpanel in my garage that I use for my welder. The subpanel goes straight to the main panel and I can see it is wired correctly. I used a new breaker and ran the line to my shop from the subpanel and am only running the CNC on it. Without the spindle running the CNC did not disconnect at all during about two hours of running. Normally without the spindle running it would disconnect after about 3-10 minutes. Two hours is longer than it could do before so I think the new line eliminated/bypassed what ever was causing the problem. Unfortunately when I started the spindle it started disconnecting again and I tried the latest suggestion from the Shapeoko tech support which was run a ground wire directly from the spindle frame to a ground prong on my outlet. Doing this has allowed me to run the CNC with the spindle running for about 1-1/2 hrs with no disconnects. I will be testing it more tomorrow. I have gotten my hopes up before.

    In summary I think I had two problems...the bad power/ground from my house and bad grounding/noise from the spindle. That is why the CNC would run fine if I turned off all of the breakers in the house except the shop but would still disconnect when I ran it with the spindle and also why it would disconnect even when the spindle wasnt running and there were other breakers on in the house. It seems like it would have been easier to see now that I know what was happening (or think I know) but hindsight is 20/20.

    Thanks for you suggestion of running the new line. It was the breakthrough that I needed to get this far.

    Also, thanks for your time in answering and being willing to help. Matt.
    You are still not done by the sound of what you have just posted

    No you have a noise problem and with correct wiring you can fix this

    This means that you don't have your spindle wired correctly, and adding a Ground wire is not the correct thing to do, so there advice was not what you should be doing

    Do you have a 4 Wire cable plus shield from the VFD to the Spindle, this is the starting point, you need to have U V W Plus Ground plus shield, what do you have, this is not a cable you can buy from your local hardware store, these are specially designed for VFD Etc use

    Mactec54


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    Default Re: Help with a bad ground

    I have four shielded wires going to U,V,W, ground and the shielded wire is connected to the same ground. I am guessing that I have a bad ground on one or both of the shielded wires. Honestly, this is the first time the machine has been working correctly since I have had it and I am nervous to mess with it again. I start work tomorrow so it will be days before I have a chance to dig in and check. I remember it was a pain to get the shielding connected to the ground but I cant remember why. Maybe its loose or has disconnected.

    Matt.



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    Default Re: Help with a bad ground

    Quote Originally Posted by BlackMaddie View Post
    I have four shielded wires going to U,V,W, ground and the shielded wire is connected to the same ground. I am guessing that I have a bad ground on one or both of the shielded wires. Honestly, this is the first time the machine has been working correctly since I have had it and I am nervous to mess with it again. I start work tomorrow so it will be days before I have a chance to dig in and check. I remember it was a pain to get the shielding connected to the ground but I cant remember why. Maybe its loose or has disconnected.

    Matt.
    This is the only way to connect the shield, and it needs to be connected at both ends to Ground, or the Ground Plane ( metal Plate that everything is mounted on in your electrical Cabinet) what you have created is not suitable even though it is running, you need to check the that the 4th Pin in the Spindle connecter has continuity to the Spindle Body, if it does not then you need to correct this, by taking the top off the spindle, and doing as in the photo below, Grounding of the shield correctly is very important

    Attached Thumbnails Attached Thumbnails Help with a bad ground-grounding-shields-3-png   Help with a bad ground-grounding-shields-5-png   Help with a bad ground-vfd-shield-grounding-png   Help with a bad ground-shield-clamp-png  

    Help with a bad ground-ground-wire-2-jpg  
    Mactec54


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    Default Re: Help with a bad ground

    I am a retired electrician, you need to find out what the problem is before you can fix it. This can be caused by many things like a drop in voltage, loose wire somewhere or even something external to your house.

    If you have a good multimeter, one that records the high and low voltage levels check it at the source of your machine to insure your getting the proper voltage consistently. Low voltages could be caused by something starting, like a microwave, water pump, heating system etc. If you do find the voltage is dropping, you need to know what is causing it, that is done by the process of elimination. Turn off all the motor circuits, except for one, and see if the voltage still drops. If not, go on to another circuit to eliminate the possible culprits. Motors take about 7 times the power to start compared to the full running load.

    Adding a ground rod is not the probable answer for your problem, even if it is noise.

    Joe Ohlandt



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    Default Re: Help with a bad ground

    Quote Originally Posted by Joe_Ohlandt View Post
    I am a retired electrician, you need to find out what the problem is before you can fix it. This can be caused by many things like a drop in voltage, loose wire somewhere or even something external to your house.

    If you have a good multimeter, one that records the high and low voltage levels check it at the source of your machine to insure your getting the proper voltage consistently. Low voltages could be caused by something starting, like a microwave, water pump, heating system etc. If you do find the voltage is dropping, you need to know what is causing it, that is done by the process of elimination. Turn off all the motor circuits, except for one, and see if the voltage still drops. If not, go on to another circuit to eliminate the possible culprits. Motors take about 7 times the power to start compared to the full running load.

    Adding a ground rod is not the probable answer for your problem, even if it is noise.

    Joe Ohlandt
    He has mostly eliminated any power problem, by running a new direct line, from the main Panel to his workshop, read the whole post, if you are not familiar with VFD Drives, which this appears to be the case then, you don't have the experience for this type of install, with the use of a VFD there is no extra draw on the electrical system they draw the rated power of the motor at startup ( its called soft start )

    Mactec54


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    Default Re: Help with a bad ground


    you don't have the experience for this type of install!!
    I guess you've been told!
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
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    Default Re: Help with a bad ground

    Al , Joe Ohlandt and Mactec54

    quote from post 1
    " I have been told by several people to just add a ground rod and ground everything close to the machine. I can do this but I have also been warned that this can cause a dangerous potential when using two separate ground on one system."


    as a matter of interest, whats the problem with multiple earths ?

    the reason I ask is at one place I worked
    the equipment had the utility earth connected to the 19" racking and the metal enclosures of the equipment

    a ground spike provided a low noise earth that connected to the isolated electronics "signal ground" that connected to the screens of dozens of video cables

    just to complicate things screened cables run into another building powered by another mains supply
    so I expect there could be a few volts difference between the two utility earths
    (its possible the building were on two different phases !!)

    working for another company
    I had to use a video isolator to prevent hum bars on monitors due to earth currents flowing between the earths in two houses
    the camera control unit / power supply being in one house and the second house used as a tv set

    mains powered tv monitors in both houses being connected to the camera


    wiring a cnc machines control box can be a black art
    not only separating the noisy power cables from the low level signal wiring
    but avoiding all the possible ground / earth loops

    do you connect both ends of the cable screens ?? - only if you all ready have both ends are at equipotential
    using a breakout board with 24V inputs instead of 5V can help or using opto-isolators for galvanic isolation

    John

    Last edited by john-100; 06-11-2018 at 03:22 PM.


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    Default Re: Help with a bad ground

    Quote Originally Posted by john-100 View Post
    Al , Joe Ohlandt and Mactec54

    quote from post 1
    " I have been told by several people to just add a ground rod and ground everything close to the machine. I can do this but I have also been warned that this can cause a dangerous potential when using two separate ground on one system."


    as a matter of interest, whats the problem with multiple earths ?

    the reason I ask is at one place I worked
    the equipment had the utility earth connected to the 19" racking and the metal enclosures of the equipment

    a ground spike provided a low noise earth that connected to the isolated electronics "signal ground" that connected to the screen of the video cables

    just to complicate things screened cables run into another building powered by another mains supply
    so I expect there could be a few volts difference between the two utility earths
    (its possible the building were on two different phases !!)

    working for another company
    I had to use a video isolator to prevent hum bars on monitors due to earth currents flowing between the earths in two houses
    the camera control unit / power supply being in one house and the second house used as a tv set

    mains powered tv monitors in both houses being connected to the camera


    wiring a cnc machines control box can be a black art
    not only separating the noisy power cables from the low level signal wiring
    but avoiding all the possible ground / earth loops

    do you connect both ends of the cable screens ?? - only if you all ready have both ends are at equipotential
    using a breakout board with 24V inputs instead of 5V can help or using opto-isolators for galvanic isolation

    John
    There is not a problem with more than ( 1 ) if they are Bonded together , check your electrical code it would be a violation if they are not bonded and correctly installed, the PDF I posted, gives you some information on Grounding / Earth connections

    There is no such this black art in a CNC electrical box, the only part that would be black, is if wired incorrect, this is are very basic wiring

    For shields it is very important to do this for VFD Drives, every manufacture will show you this in there installation drawings, and in some countries it is a code requirement

    Mactec54


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    Default Re: Help with a bad ground

    Hi Mactec54

    I take it as read that in the UK
    an installation designed by electrical engineers
    2 separate earths / grounds that are deliberately kept separate
    will be with in UK regulations

    my question was prompted by the quote from post 1
    so its a question of whats accepted in other parts of the world

    from your answer it looks like the NA code is different in this regard

    avoiding all the possible ground / earth loops in your control box depends on detailed information of all the component parts / modules
    some parts come with very poor manuals that don't show all of the internal interconnections that result in unintended
    ground loops

    other times a damaged screen wire can result in an earth loop long after the machine was commissioned


    John



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    Default Re: Help with a bad ground

    Quote Originally Posted by john-100 View Post
    Al , Joe Ohlandt and Mactec54

    quote from post 1
    " I have been told by several people to just add a ground rod and ground everything close to the machine. I can do this but I have also been warned that this can cause a dangerous potential when using two separate ground on one system."


    as a matter of interest, whats the problem with multiple earths ?



    John
    See page V1 V11 & V111 comments.
    Mutiple earth ground connections such as ground rods without being bonded can and usually do cause ground loops.
    BTW, my Electrical training was in the UK, and in service installations the supply Co did not supply an earth ground and it had to be established by ground rod or water pipe locally, and also the neutral was only connected to earth at the transformer, never in the service panel.
    As it is in N.A.

    Al.

    Attached Thumbnails Attached Thumbnails Help with a bad ground-grounding-pitfalls2-pdf  
    Last edited by Al_The_Man; 06-11-2018 at 04:24 PM.
    CNC, Mechatronics Integration and Custom Machine Design

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    Default Re: Help with a bad ground

    Hi Al

    before I study you PDF file

    in my example
    the unusual separate earths / ground example works because the utility earth is for safety to protect you from an electrical shock

    the earth spike is connected to the equipments signal ground that's isolated from the mains earth

    yes, an accidental connection between the two does result in an earth loop resulting in mains hum on the signal

    It was the statement in post 1
    " I have been told by several people to just add a ground rod and ground everything close to the machine. I can do this but I have also been warned that this can cause a dangerous potential when using two separate ground on one system."

    I was trying to find out what the danger is
    I can see an accidental to a gas pipe can be a hazard but not 2 or more earths
    (unless the wires is too thin for the resulting current [ not that I expect 16mm cable to be] )


    John



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    Default Re: Help with a bad ground

    There probably is minimum personnel danger from two distinctly separate grounded earth rods if done correctly, I would suspect the detrimental effects would be on equipment mis-behaviour due to different possible differentials between the two.
    The PDF explain some of mistaken reasoning with using local ground rods.
    Actually I never did understand the rules we had to comply with in the UK in order to get the OK from an inspector if inadvertently we had a connection between earth and neutral at the service entry, which had to be corrected before service would be allowed..
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

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    Default Re: Help with a bad ground

    Hi Al
    I am not sure if harmonisation with europe has any thing to do with it but
    new utility mains supplies have a combined earth & neutral in the underground 3 phase supply cable
    instead of a separate neutral wire with the steel armour doubling up as the earth

    your earth and neutral wires join to the utility combined earth & neutral terminal where it enters the property !

    some times the separate earth & neutral wires join to the combined earth neutral where your service cable is spliced into the under ground supply

    not sure if I have this totally correct but this is what I have so far

    Help with a bad ground-uk-verse-na-earthing-jpg

    another variation not shown in the diagram is where the cables combined earth & neutral is earthed are regular intervals along its length

    John



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    Default Re: Help with a bad ground

    Quote Originally Posted by john-100 View Post
    Hi Al
    I am not sure if harmonisation with europe has any thing to do with it but
    new utility mains supplies have a combined earth & neutral in the underground 3 phase supply cable
    I left just before decimal currency!
    I imagine a lot has changed since .!.
    Including the metrication of wire size!
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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