Centroid Community CNC Support Forum

martyscncgarage wrote: ↑Wed Feb 09, 2022 8:44 am

cncsnw wrote: ↑Wed Feb 09, 2022 2:59 am Where you have 12ga wires paired with 6ga wires at the top of the 40A breaker, be sure to give each 12ga wire a firm tug after you are done tightening the terminal screw, to be sure it is secure.

With a pair of wires of greatly differing size, it is hard to get the smaller wire adequately clamped.

If/when you mount switching power supplies behind the Oak unit, be sure that the terminal screws peek out far enough to be readily visible and accessible (maybe 3/4" clear of the edge of the Oak mounting frame).

Marc gives good advice. I poke my power supply terminals out from underneath Oak or All in One DC so you can measure voltages.
I personally like to take all the grounds to one place and use a ground buss bar.

Marty

With regard to grounding I'm on the same page and agree with you Marty. i went to the orange box store tonight and picked up a buss bar i really detest the long threaded ground studs with multiple ring terminals, it drives me bonkers at work especially when there are multiple studs and they are all different sizes! they are a real pain if you want to remove one ground on the bottom of the stack as you have to undo all of them.

AshG wrote: ↑Thu Feb 10, 2022 12:38 am i know what you mean regarding the 12ga pairing up to the 6ga, as i cable tied it one started to pull loose...

I recommend installing wire ferrules on all wires for this reason and to prevent shorts when one "wisker" doesn't make it into the terminal.

+1 for wire ferrules.
As for wire size vs. the overcurrent device protecting it. This has always been a gray area for me. The wiring in a control cabinet is not in a conduit. So, I tend to treat it as "Chassis Wiring"
American Wire Gauge Chart: https://www.powerstream.com/Wire_Size.htm
This is a good chart: https://cdn.automationdirect.com/static ... iremtw.pdf
Insulation type plays a large factor as well.

MTW has an insulation rating of 105c according to this article;
https://www.awcwire.com/allied-universi ... tw-vs-thhn#

I would bump it up to #10 copper and to be completely safe go to #8 MTW (machine tool wire is the most flexible)
Marty

While MTW may be rated to 105c, you have to design around the LOWEST temp rating on the wire run. If your 105c conductor goes to a 60c rated fuse block, then you have to use 60c ampacity ratings.

thanks some really good info there guys. i have boxes of ferrules. i still have to label all the wires so i will have to do the ferrules when i do that.

here is a snap of my acorn cabinet i built a few years back for the other mill, its been running like a champ, also..... note extensive use of ferrules

Made a bit more progress only getting the odd hour here and there to work on it at the moment. The power distribution wiring is taking shape, got a lot of stuff final mounted and started labeling the wiring, still scratching my head on where i want the ground strip.

Here is the current state of the cabinet relays and terminal strips for them are in all the dc power supplies are properly mounted now, i moved them out a bit more based on recommendations from Marc and Marty. power distribution for the axis drives is pretty much done. drive power is wired and labeled (fyi max diameter wire you can get into a DMM terminal is 12ga) will hopefully get to wiring up the oak and the 1616 on the weekend.

Looking good Ash. How about putting the ground buss under the right most line fuse along side where the machine cables enter the cabinet? Just a thought.