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  1. #1
    Join Date
    Mar 2018
    Posts
    70

    Size for ground wires

    Hi,

    at the moment I'm building the control panel and could need a little help with the size of the ground wires.


    The source wire is 1,5mm^2. All consumers are internal connected to a star point. Would it be a problem if the consumers ground wires to the star point are thicker (2,5mm^2) than the input source ground wire or is it necessary that the wires to the star point are smaller than the source wire?


    Here are some pictures: (In the future all ground wires will go to ground temrinal blocks on a rail..)

  2. #2
    Join Date
    Jan 2005
    Posts
    107

    Re: Size for ground wires

    Never smaller .Larger ok.

  3. #3
    Join Date
    Mar 2018
    Posts
    70

    Re: Size for ground wires

    Ok. Thanks. Another question:

    As you can see on the picture the panel has three line-in wires. Each one with hot/neutral/ground.


    I would like to crimp their grounds together and use them like one large ground wire. Is this a problem?

  4. #4
    Join Date
    Dec 2003
    Posts
    24216

    Re: Size for ground wires

    The Ground wire should be the same gauge as the supply conductor or same as the combined size, if supply is from difference sources.
    All ground wires should terminate at the star point or be joined and continued with a single conductor equal to the combined gauges.
    The service ground should also terminate at the Star Point GND.
    There was a copy of NFPA79 out there if needing guidance on regs for enclosure wiring.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

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

  5. #5
    Join Date
    Jan 2005
    Posts
    15362

    Re: Size for ground wires

    Quote Originally Posted by millhouse_ View Post
    Hi,

    at the moment I'm building the control panel and could need a little help with the size of the ground wires.


    The source wire is 1,5mm^2. All consumers are internal connected to a star point. Would it be a problem if the consumers ground wires to the star point are thicker (2,5mm^2) than the input source ground wire or is it necessary that the wires to the star point are smaller than the source wire?


    Here are some pictures: (In the future all ground wires will go to ground temrinal blocks on a rail..)
    This is a good question, so if other devices require or have a larger Ground wire, this could indicate that your main supply is to small 1.5mm is only 15 Gauge ( close enough to 16 Gauge ) most cabinet's need at least a 30A supply which would be 10 Gauge, so I would say you input supply is a little on the light side

    What size is the VFD Drive ??? this will need a Power Filter on it input supply

    The Mains Power Supply Ground Connects at the Star Point
    Mactec54

  6. #6
    Join Date
    Jan 2005
    Posts
    15362

    Re: Size for ground wires

    Quote Originally Posted by millhouse_ View Post
    Ok. Thanks. Another question:

    As you can see on the picture the panel has three line-in wires. Each one with hot/neutral/ground.


    I would like to crimp their grounds together and use them like one large ground wire. Is this a problem?
    That is not a good Idea, how can you have 3 Main Power Supplies from 3 different power outlets, you should only have ( 1 ) for your whole cabinet
    Mactec54

  7. #7
    Join Date
    Mar 2018
    Posts
    70

    Re: Size for ground wires

    Thanks for the feedback.


    The first power input is for the 5v and 12v power supplies and maybe for other stuff in the future like a vacuum cleaner etc. And it is connected to a contactor that switches on the other two inputs ( one for the steppers and one for the spindle ). Normally I would have used 3-phase current for this but I don't have the possibilities for this.

    @mactec54

    The consumers don't need 2,5mm^2. I just used it for them.

  8. #8
    Join Date
    Sep 2005
    Posts
    1740

    Re: Size for ground wires

    We routinely build control panels for production lines with multiple power sources and grounds. They are all sourced from the building main 13.8 Kv and substations. All grounds are tied back to the main substation. It makes no difference. Your control panel needs a disconnect for each source.
    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP

  9. #9
    Join Date
    Jan 2005
    Posts
    15362

    Re: Size for ground wires

    Quote Originally Posted by millhouse_ View Post
    Thanks for the feedback.


    The first power input is for the 5v and 12v power supplies and maybe for other stuff in the future like a vacuum cleaner etc. And it is connected to a contactor that switches on the other two inputs ( one for the steppers and one for the spindle ). Normally I would have used 3-phase current for this but I don't have the possibilities for this.

    @mactec54

    The consumers don't need 2,5mm^2. I just used it for them.
    Ok what size is the Spindle Motor and VFD Drive how many Kw and Amps
    Mactec54

  10. #10
    Join Date
    Jan 2005
    Posts
    15362

    Re: Size for ground wires

    Quote Originally Posted by wmgeorge View Post
    We routinely build control panels for production lines with multiple power sources and grounds. They are all sourced from the building main 13.8 Kv and substations. All grounds are tied back to the main substation. It makes no difference. Your control panel needs a disconnect for each source.
    "Routinely build control panels" the last control box you used I recall you brought it already made for your hobby machine
    Mactec54

  11. #11
    Join Date
    Dec 2003
    Posts
    24216

    Re: Size for ground wires

    Quote Originally Posted by millhouse_ View Post
    Ok. Thanks. Another question:

    As you can see on the picture the panel has three line-in wires. Each one with hot/neutral/ground.


    I would like to crimp their grounds together and use them like one large ground wire. Is this a problem?
    One example is DIN rail mount terminals, you can get them with automatic ground to the enclosure, they are half green, half yellow, and are intended for such cables that also include a ground conductor.
    The ground in this instance is through enclosure bonding, but also pays to take a single correctly sized one to the star point also.
    This is the method I have used for over 50yrs.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

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

  12. #12
    Join Date
    Sep 2005
    Posts
    1740

    Re: Size for ground wires

    Quote Originally Posted by mactec54 View Post
    "Routinely build control panels" the last control box you used I recall you brought it already made for your hobby machine
    Before I retired and started drawing the bucks for not working… just being a hobby guy. Yes even my hobby panels are wired to Code. We wired some pretty good sized industrial plants.

    Looks like Al and I did the same work.
    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP

  13. #13
    Join Date
    Dec 2003
    Posts
    24216

    Re: Size for ground wires

    Quote Originally Posted by wmgeorge View Post

    Looks like Al and I did the same work.
    Could be.
    Mostly retro fits, PLC control panels and CNC retro fits with Fanuc and Mitsubishi, designed a few custom ones with Galil motion cards, which are a pleasure to use.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

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

  14. #14
    Join Date
    Sep 2005
    Posts
    1740

    Re: Size for ground wires

    Quote Originally Posted by Al_The_Man View Post
    Could be.
    Mostly retro fits, PLC control panels and CNC retro fits with Fanuc and Mitsubishi, designed a few custom ones with Galil motion cards, which are a pleasure to use.
    Al.
    Not the same. I installed and wired production lines, moved old junk machines at times into the modern world. Plus new stuff also, some PLCs. some solid state control systems as prototypes and just a lot of MCC wiring to machines and tying in interlocks and the like. At the time I was working under a very strict Master Electrician. Later on I was the sole electrician for second shift production. Loved every minute of my electrical work. Later got into Commercial HVAC/R work specialized in controls.
    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP

  15. #15
    Join Date
    Mar 2018
    Posts
    70

    Re: Size for ground wires

    This is it now:





    Attached Thumbnails Attached Thumbnails 2222.jpg   3333.jpg   5555.jpg  

  16. #16
    Join Date
    Mar 2018
    Posts
    70

    Re: Size for ground wires

    @mactec54

    It is a basic setup. 4x High torque Nema-23 Stepper, 2.2kw Spindle

    But I want to upgrade later and don't want more than 10A per line-in.





  17. #17
    Join Date
    Jan 2005
    Posts
    15362

    Re: Size for ground wires

    Quote Originally Posted by millhouse_ View Post
    @mactec54

    It is a basic setup. 4x High torque Nema-23 Stepper, 2.2kw Spindle

    But I want to upgrade later and don't want more than 10A per line-in.




    2.2Kw Spindle you are not going to run it on a 10A circuit even a 20A circuit won't run it without problems, the minimum circuit to run a 2.2Kw spindle is 25A at 230v
    Mactec54

  18. #18
    Join Date
    Dec 2003
    Posts
    24216

    Re: Size for ground wires

    Quote Originally Posted by millhouse_ View Post
    This is it now:
    I see you are already using the DIN rail GND terminals!
    Some cable trough would have neaten'd it up a little!
    Max.
    CNC, Mechatronics Integration and Custom Machine Design

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

  19. #19
    Join Date
    Mar 2018
    Posts
    70

    Re: Size for ground wires

    @mactec54

    As far as I know those 2.2kw + VFD sets won't exceed 8A.

  20. #20
    Join Date
    Mar 2018
    Posts
    70

    Re: Size for ground wires

    @al_the_man

    Just added them yesterday to replace the messy wiring with the enclosures ground pin. Not a beauty but it's still a work in progress.

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