We used to mount the DIN (German Industry Standard) rails hard against the back panel, but then it was tricky to lay panel wires out the bottom of of one component and then to the top of the next component. Now we stand the DIN (Deutsche Industrie Norm) rail up on spacers so that we can pass the wires under the rail. Snag with this is that tracing the wires can lead to mistakes because they get hidden. (A dental mirror is useful for this tracing).

Here is a mix of top & bottom feed, even with the rail up on spacers. But I think that the flow is fairly logical. As you say, labelling and diagrams also help a lot. I just wanted your opinion if bottom feed might be against any codes?

I don't think it is against any codes in the US. The one I ran into was a US made, UL approved, digital DC drive package built by Reliance Electric.

Hopefully the last question on the bottom/top issue: Would any laugh if I fed this contactor (as an example) from the bottom on the T1 T2 T3 terminals? I reckon that turning the contactor over for upside-down markings is a worse crime to commit.

As far as bottom feeding a contactor, I'm not sure. The only example I found was another Reliance Electric design, but they had relabeled the terminals. I found this short discussion also but I don't have the NEC handbook.

http://forums.mikeholt.com/archive/i...p/t-62360.html

I also began to question the wisdom of switching the neutral. Again, there seems to be no definite rules against it I could find other than the mention below, and it may be referencing switching only the neutral. I don't remember it being something that is typically done in the US since the neutral is bonded to ground.

http://www.isa.org/Template.cfm?Sect...ontentID=40708

On bottom feeding, thanks for finding that discussion, and let's just avoid it altogether. (I plan to make more graphical drawings of the components on the DIN rail and you have helped me tremendously with real industry feedback)

Switching of the neutral is something that Mike R also had big problems with, but he eventually relented when it was made clear that we only switch the neutral simultaneously with the Lives (Hots) on a single multipole switch or contactor. We never think of the Neutral as something that is connected to Ground (Earth). In fact, because we have lots of Ground Fault Protection, touching Neutral to Ground (Earth) causes a trip (fault). Look at all continental Europe 2-pin plugs for 230V - they can be inserted any way around.

Snag is, we sometimes find that an idiot swops Neutral & Hot (Live) in a distribution board upstream and we are never 100% sure which of the two wires is 230V above ground potential. Maybe something similar to the US 230V single-phase where BOTH wires are treated with equal respect.

Bottom line is that we prefer switching both wires, but only in a switch that forces them to be switched simultaneously. However, since I am going to end up producing circuits for the America's versus the non-America's, I can avoid neutral switching in the one case.

Mike N, the simultaneous disconnecting of all Lives(Hots) and Neutral is equivalent to pulling the plug - what could be safer than that? :)

Well, yes and no. One of the issues with E-Stops in general is all of the new safety regulations that go with them. Depending on the assessed level of hazard to life and limb, it can get very pricey to properly construct an E-Stop circuit. This is true in the US as well as Europe. Worst case involves redundant contactors, safety relays (very pricey), and two pole force guided E-Stop pushbuttons.

The problem with breaking the neutral is that you don't know that it or the hot, really did break. Welded contacts are a fact of life. If you are holding a plug in your hand you can visually (or tactiley if you are vision impaired) tell that that all circuits are indeed disconnected.

Mike, to the best of my knowledge, the Ensto multipole disconnect switches that I am promoting here, embody the principles of "safety relays" and "two-pole force guided E-Stop pushbuttons". These Ensto's are force-break or positive action switches - a single welded contact prevents the handle from turning and prevents any other pole from opening.

That's good. And I was actually addressing the contactor as opposed to the disconnect switch. It's the reason redundant contactors are required in the applications that are considered to be more hazardous. I attended a three day "school" on safety devices and their use and application. All through the training it was repeatedly stressed that we were not to determine the hazards involved or suggest devices needed. The end user or equipment manufacturer was required to do that or they could contract a qualified (abundantly insured I'm sure) safety engineering firm to make the assessment as to what was required. My only intent is point out possible issues based on my expereince with equipment failures over the years.

Mike your words have been very much appreciated. The readers keeping an eye on this thread must have noticed:

- how tricky this subject can get and some of the risks to be considered,

- that it is not a simple DIY project to be tackled lightly

- how unqualified I am to be the guide in this area

Mike, how common is Ground Fault Protection over there? Would if be reasonable to specify that a MechMate can only be connected to a fused outlet with GFI? Out here that would be the de facto situation.

On a factory floor, it isn't common at all. Per NEC code, it is required in newly built or (re)wired home garages, kitchens, baths and outdoor receptacles. But most older garages don't have GFI and they are basically "grandfathered in" since they've already been inspected. I believe a dedicated, hardwired device in a garage, such as an air compressor may be exempt from the GFI requirement, but I won't swear to it. The NEC code is open to interpretation by the building inspectors and different municipalities may use different editions as their code book. It's a real mess really.

As far as requiring GFI protection, it would certainly be a good idea. Considering the wiring is being done mostly by nonprofessionals and that wiring is in motion, it would be a small price to pay to avoid the potential shock hazard. Despite the best grounding efforts it would still be possible to have exposed wiring a person could come in contact with, without it necessarily grounding out.

Installing a GFCI
 

Installing a GFCI : an article found on the web.

(Ground Fault Circuit Interrupt)

I would like to offer this as a possible main power/E-Stop schematic. I am know the symbols are not standard, but I think you can get the idea. What we have is the a relay similar to what you have spec'd earlier except with a 24V control, and next to that is a 24V transformer. When the on button is press, the relay will transformer will turn on, energizing the relay, witch will then continue to feed the transformer after you have releaced the button. The benefits to this setup are, the power will remain off after a power outage, less high voltage wireing running through all the moving parts, and it also gives you a good source of power for iluminated switches.

Brian, 24V control is common in industrial electronics, but I am loathe to introduce yet another voltage into the control box - we have enough confusion in there already. The other benefits you mention are already present:

"The benefits to this setup are, the power will remain off after a power outage, less high voltage wireing running through all the moving parts, and it also gives you a good source of power for iluminated switches."

Our latching circuit also stays off after a power outage and illuminated switches for 115V/230V are also easily available.