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Thread: 4x8 CNC router question

  1. #1

    Question 4x8 CNC router question

    I just bought a 4x8 cnc router with vacuum table and I would like some help with the correct size amp circuit breaker. This one of the Chinese cnc router and the manufacture support isn't really helping with this part. Someone says they are running similar on 35amps but I feel like that a bit too low. Here are the specs. All of these are connected together to the same control box. I appreciate any help. Thanks


    Spindle power: 4.5 kw HQD
    Vacuum pump 2.2kw
    Inverter :Fuling VFD 5.5kw
    Leadshine dm860h drivers and Leadshine stepper motors

  2. #2
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    5.5 Kw at 240V is roughy 23A. This should be fine with a 30amp circuit properly wired with 10 gauge copper. The vacuum will need to be on a separate circuit.

  3. #3
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    I agree with Michael, but there's no harm, other than cost, in provisioning for 40 amps just to be sure. My 1.7kw machine requires 30 amps per my manufacturer.

    And yes, the vacuum pump must have its own dedicated circuit.
    --

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

  4. #4
    Quote Originally Posted by Michael Burnside View Post
    5.5 Kw at 240V is roughy 23A. This should be fine with a 30amp circuit properly wired with 10 gauge copper. The vacuum will need to be on a separate circuit.
    Hi Michael,
    I thought the pump is suppose to go through the controller box so I can use the on/off button that's built into the controller box for the vacuum pump. It came pre-wired like that already. I could remove the wires and run it separately. What amps would I need for 2.2kw vacuum pump?

    Thank you

  5. #5
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    I would highly doubt that they would wire them to the same circuit. But I don't know your machine specifically. I would personally find that annoying since I only turn on my vac when I need it on for z-zero and when I'm running the job. Plus I don't always use it but obviously the VFD needs to be on to do any job.

    A 2.2kw vac would pull about 9-10 amps max. I have a 2.5kw wired to a 30A dedicated circuit. You don't need 30A as a typical 240V circuit with 12 gauge would get you 20A and 10 gauge would get you 30A if wired properly by an electrician. The nice thing about having it separate and only 9 amps is you can use a remote switch, like the PSI Woodworking LR220-3 Long Ranger III, for less than 100 bucks and remote switch your vac on/off as needed. I'm almost certain they would not combine into one plug.

    Current is additive, so if you budgeted for 23+10 plus a little guardband you're looking at a 50A circuit and 8 gauge wiring (they do make 40A breakers but you'd still need 8 gauge since 10 gauge is only rated at 30A) . I only have one of those in my shop and it was very expensive to wire! If they do come combined you should discuss with a qualified electrician since the combined circuit has a much higher demand that is typical of a residential environment.
    Last edited by Michael Burnside; 01-09-2023 at 4:16 PM.

  6. #6
    Quote Originally Posted by Michael Burnside View Post
    I would highly doubt that they would wire them to the same circuit. But I don't know your machine specifically. I would personally find that annoying since I only turn on my vac when I need it on for z-zero and when I'm running the job. Plus I don't always use it but obviously the VFD needs to be on to do any job.

    A 2.2kw vac would pull about 9-10 amps max. I have a 2.5kw wired to a 30A dedicated circuit. You don't need 30A as a typical 240V circuit with 12 gauge would get you 20A and 10 gauge would get you 30A if wired properly by an electrician. The nice thing about having it separate and only 9 amps is you can use a remote switch, like the PSI Woodworking LR220-3 Long Ranger III, for less than 100 bucks and remote switch your vac on/off as needed. I'm almost certain they would not combine into one plug.

    Current is additive, so if you budgeted for 23+10 plus a little guardband you're looking at a 50A circuit and 8 gauge wiring (they do make 40A breakers but you'd still need 8 gauge since 10 gauge is only rated at 30A) . I only have one of those in my shop and it was very expensive to wire! If they do come combined you should discuss with a qualified electrician since the combined circuit has a much higher demand that is typical of a residential environment.
    Thank you for the help Michael. I'll wire it 8 gauge with 50amp circuit and see how it goes from there. Also, In the controller box, I do have the option to turn the vacuum on and off without the spindle and I could probably install the remote switch there if needed in the future.

  7. #7
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    If they are providing actual power to the vacuum pump via the main connection to power rather than just providing on/off control, then that absolutely has to figure into the feed to the machine. So going with the higher amperage supply makes a bit of sense, Sam.
    --

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

  8. Most of these cabinets provide only control for the vacuum pumps and dust collectors and have separate power inputs for each item via separate buss bars. But obviously a picture of the control cabinet in question would help.
    My machine needs single or 3 phase power input for the VFD/spindle. (both work, but single phase may limit the max power based on VFD size), 220v power inputs for each vac pump and dust collector, and a separate 110v line for the computer if using 3 phase for the spindle input. I am running a large 100 amp sub panel close to the machine and running individually sized power lines for each of these items on their own breaker. This sizes the over current breaker and wires for each load and reduced the risk of a single large wire input and breaker overloading the smaller ones in the cabinet.

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