View Full Version : Question about machine mains electrical hookups.

05-23-2012, 06:03 PM
I won this DIN rail on the bay with a bunch of fuseholders & connection blocks to use in wiring up the ORAC CNC. I didn't even know what they were until macona enlightened me...thanks Jerry!

In hooking up the mains power (115V) side of things, is it "kosher" to connect the hot side through the big fuse (with an appropriate size fuse) jump over to one of the multiple connector blocks to split the hots out to the power supply for the contactor coil and to the contactor contacts? It will be inside a cabinet but the mains power will be somewhat exposed to errant tools if one were working on it.

Also, is it OK to connect the neutral side up to a multiple connector block to connect up all the devices' neutrals? I guess my question is should all the mains power connections be inside a "legal" box even if it's inside a machine enclosure?

I hope my question makes sense.:o


05-23-2012, 06:12 PM
Yes you have the right idea, I generally come out of the disconnect and jumper across the necessary bank of fusing and then drop out to the applicable circuits.
The centre ones are breakers I assume?
Those jumpered block are intended for the reason you mention.
BTW, Legendboy here has a PDF copy of the NFPA79 which is the required reading for Electrical Control of Industrial Machinery.
Get him to send you a copy.
It will give the 'Code' side of things inside the cabinet.
BTW set up a common star point ground point and bond all machine grounds to it as well as the service ground, do not re-reference the neutral to it however.

05-23-2012, 06:35 PM
Awesome, thanks Max. :) The center ones are 5mm fuseholders. They're pretty cool; the black part pops out & turns 90 deg. for access to the fuse and each one has a clip in it to hold a spare fuse. I wish I'd known about this DIN rail stuff a long time ago. I don't get out enough apparently.

I had to look around a bit but got the one shown pretty reasonable. It's about 18" long and was completely filled with neat little gizmos. More than I'll use for this project but I'll find places to use them later for sure.

05-23-2012, 08:47 PM
Surprising what comes DIN rail mount now, contactors, power supplies, even transformers!.

05-23-2012, 11:14 PM
Surprising what comes DIN rail mount now, contactors, power supplies, even transformers!.
Max....and even the KB speed controllers can be fitted with a #9995 DIN rail mount kit!:D

J Tiers
05-23-2012, 11:15 PM
Surprising what comes DIN rail mount now, contactors, power supplies, even transformers!.

It doesn't make the DIN mount any more solid and vibration-proof, though. I find the DIN mounts are usually loose and floppy, requiring tight end blocks to hold things reasonably solidly.

At least the wire blocks are pretty solid, its the "stuff" that is DIN mount that is so darn loose and rattly.

I find MANY such european "systems" to be excessively "consumer grade", with much design effort apparently spent to make them "just barely good enough for light duty". If there is anything *worse* than the old-time "DIN connector" that was used for home stereo stuff, as well as computer keyboards, I haven't found it yet. The computer ones often worked OK, but the others went bad if you just looked at them real hard.

And, I am convinced there is a different but physically compatible standard for industrial DIN mounting.... we had a Holzher saw at the prior employer, with everything electrical DIN rail mounted, and the components were rock solid in there. NOT the experience I have had with nominally same stuff when building equipment.

05-23-2012, 11:24 PM
I agree. Din rail must have the end clamps or it's worthless.. and I can't believe how many I see without them.

Not only the components noted above, but the VFDs are often din rail mount. But... far too much mass for my liking without additional support.

05-23-2012, 11:27 PM
Surprising what comes DIN rail mount now, contactors, power supplies, even transformers!.

Yup, and even VFDs. When I bought my current lathe my brother (industrial electrician/electronics wiz) bought me a cheap DIN mounted east asian VFD and we wired/mounted it using a spare small chunk of rail that he had. Being that its a mechanically vairable speed machine anyway (so only run at 60 Hz), we mounted the rail inside of the base hanging out over the motor. Neat and hidden.