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  1. #11

    Mulling over the option of putting my control box into my 19" rack with the servers, I think I have a snag with that, but could use an opinion:

    I was intending to run a seperate 32A RCD spur for sole use of the CNC machine and all its electronics (including the PC that will run Mach3). Taking the advice above, if I run all the shielding and earth points back to a star point in the 19" rack mounted case and then onto the 32A earth feed, am I creating a ground loop with the existing 15A feed's earth supplying power to the existing rack mounted windows servers via two rack mounted distribution bars? i.e earth will have two paths back to the consumer unit 1. through the 32A spur's earth and 2. through the 15 Amp ring's earth?

    If that's the case I see a few options:

    1. Buy a new control case (not a problem but does mean I use some valuable workshop/office real estate
    2. Use the existing rack mount server case but isolate it from the rack, so that the two earth paths (15A and 32A) are seperated - tricky to do, as the case is bolted to it rails and hence the 19" rack itself.
    3. Up the rating on the 15A circuit and run the servers and the CNC off of the same circuit - risks dirty power to my precious data/server hardware
    4. Stop drinking Redbull at night and conjuring up problems where they might not exist ;-)

    I'm about to order the shielded cabling, e-stop button, limit switches this weekend, so any help would be most appreciated, as I can add a new control box to the order if its needed.

    BTW - what do you guys normally use for limit switches - RS has some pretty exotic looking kit, but if I can use a suitably rated momentary single pole then I'm all for shaving a little cost.



  2. Hmmm... as long as the 15A and 32A are on the same phase, from the same consumer unit, I dont see any issue with taking the earth from both of them to the star point. It won't create a ground loop within the downstream equipment and thats the main reason for the star point - to avoid differential ground voltages impacting the sensitive signalling.

  3. #13
    ah thanks Irving - they are both from the same consumer unit on the same phase, so the "earths" are going back to the same point in the office/workshop.

    That's good news then as I have gutted the antiques I found in the unused rack mount server case and already made a mod to the 5-1/4 drive bay so it can accomodate my drivers and have a 120mm fan to cool them. Just waiting for my shielded CY 16A rated cable to arrive on Mon/Tues to start hooking stuff up and doing the cable runs. I think it may be time to start a build log :-)

    Cheers and thanks again


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