Correct Conductor Marking

[iant]

I have been in the trade (started my apprenticeship in 76) for 36 years.
I was never tought to use two different numbers at either end of the same cable.
This guy is playing games with you.(F###ing you over about his mistake)
Unless he did the drawings and you accepted his final draft prior to you accepting the 'ASBUILT' drawings

 

[Mihaylov]

I bring this thread back to life to ask some questions.

In your posts you told me that you mark each conductor with a unique number at both ends. If I renumber my first example in this way it would be:

(S1)-|105|----|105|-(X2:5)-|106|---|106|-(X1:3)-|107|---|107|-(X10)
Where (.) shows the device: S1 - sensor or button, X1 & X2 - terminal strips, X10 - PLC input; |.| shows the conductor number.

or you mean the following:
(S1)-|105|----|105|-(X2:5)-|105|---|105|-(X1:3)-|105|---|105|-(X10)
Signal 105 connects S1 and X10.

When I drew a wiring diagram as the first example, everyone told me that this is wrong because both conductors connected to one terminal should have the same marks on them. Is there such a rule in the world or this is true only in my part of Europe?

Other questions that I would like to ask are:
- Are the terminals for connecting the motor to the cabinet always named U, V and W?
- What numbers do you use for 24V DC power supply lines: L+ and M as some standards say, 24V and 0V or another?

I would appreciate if you send me a piece of real wiring diagram just to compare the different numbering.

Regards,
Mihaylov
mihaylov.s(at)gmail.com

 

[iant]

your first and second examples are both OK as you may want to be able to install a new device between terminals X2:5 and X1:3. this is good practice.

there are many accepted wire numbering standards each have advantages and dissadvantages - the logic of the numbering system makes fault tracing easier. Some numbering systems detail the Page No. and the Rung of that Page and the Type of part.
eg. 12S14 (12) page No. - (S) Switch - (1_) rung No. - (_4) Line Position

Motor Terminals are usually always U,V,W and U1,V1,W1 (Delta)

L+,M is Seimens Std. 24V, 0V is the designers choice.
it could well be +V -V

 

[The Plc Kid]

All I can say about the contractors method is WTF!!!

 

[iant]

All I can say about the contractors method is WTF!!!

you got me beat?
the method I was stating is used, but not commonly and definately not by me - too invloved and not good for simple wiring changes.

 

[DamianInRochester]

For DC votlage, i detest the practice of labeling the common wire with a negative sign. Can't say how many times I have seen a single 24VDC supply with +24Vdc labeled +24V and common labled -24V. It is not -24V, it is common. How about 24C or 24COM or 24VCOM? What if you actually have a dual power supply as often happens with a 12V supply. If you label common -12VDC then what do you lable -12VDC as, -(-12VDC)??

For power taps I prefer using descriptive labels as opposed to drawing addresses. If I have for example one +/-12V supply and 2 24VDC supplies, my tags would go like this:

"+/-12VDC supply"

+12V-101
+12V-102
+12V-103, etc
12COM
-12V-101
-12V-102, etc

"For 24V ps 1"

24V-101
24V-102
24V-103
24VCOM

"For 24VDC ps 2"

24V-201
24V-202
24V-203, etc.
24VCOM

If I want the commons to be isolated from each other or un-grounded, I will instead use

24C-100 and 24C-200

Basically after every fuse I just give it a new number.

If I have a 24Vdc signal that goes through the MCR or Estop (for output card power or something) I will drop the V and use Q. So for Output Card 1 I will have a separate fuse with 24Q-105, and next card is another fuse with 24Q-106, etc.

Using the drawing#/Line# scheme is the most prevalent, but makes it more difficult to diagnose things without the prints. You also have situations where by using the arbitrary address makes #s of different voltages scary close to each other. For example, 115vac and com may be labled 52601 and 52602. And 24Vdc and com may be 56201 and 56202. It would be easy to jumble those numbers in your head while working on a panel and land a 56201 on a 52601. The wire number does not embed any information about the signal. However it would be difficult to expalin how you landed a wire labeld 24V-101 on a terminal labeled 115vac-101. From a maintenance perspective, I always think it is nice to build the information into the system. Wire # 51223 tells me nothing, but +5VDC-1 gives me a clue.

Not saying it is right or wrong, just food for thought.

I have also seen the L+ and M scheme used. I'm not too fond of it. I prefer to see more fused sub circuits. Maybe then you could have at least 1L+, 2L+, etc. If you have everything on the panel tapped to the same fused circuit, it takes too long to find the source of a short circuit or overload. I like seeing a separate fuse for at least each output card, preferably on each intput card, and to each component that requires power (HMI, Enet Switch, etc). Having these individually fused also helps at debug time because you can use the fuse holder as a switch to turn ON/OFF subcircuits.

 

[iant]

you are right Damian
Using the negative sign is not good practice as you can have negative voltages. +12/0/-12 for an example.

And I also agree with you points on the - drawing#/Line# issues
But when a customer wants it they get it.

and 100% for the stepping of the numbers as you have shown.
I prefer that also

 

[Lancie1]

For DC votlage, i detest the practice of labeling the common wire with a negative sign. Can't say how many times I have seen a single 24VDC supply with +24Vdc labeled +24V and common labled -24V. It is not -24V, it is common.

Damian,

Now you are getting away from DC wiring and straying into Philosophy.

Every DC circuit has a + and a - side. If you do not believe this, look at the terminals of any battery. Whether you label the terminals as such is a matter of preference. Some DC circuits are connected to a ground and thus also become defined as 0 volts (TO EARTH ONLY) or COMMON, although they still have the same negative (-) relationship to the DC power supply.

For me, worrying about piddling stuff like this is wasting valuable time out of my limited 79+ years.

 

[DamianInRochester]

Damian,

Now you are getting away from DC wiring and straying into Philosophy.

Every DC circuit has a + and a - side. If you do not believe this, look at the terminals of any battery. Whether you label the terminals as such is a matter of preference. Some DC circuits are connected to a ground and thus also become defined as 0 volts or COMMON, although they still have the same negative (-) relationship to the DC power supply.

Hi Lancie, I respectfully disagree. The reason is "ambiguity".

I can ground the (+) terminal on the battery and have a negative power supply.

If I do this on a panel, is it still appropriate to label the wire +12VDC and -12VDC? I wouldn't allow it. If you label something in reference to "common", regardless of how you choose to define common, you eliminate the ambiguity and confusion.

Again, it brings me back to my question. If you have two 12VDC batteries tied in series, what are you going to label the wires?

In my world you could label them (0VDC/-12VDC/-24VDC, +12VDC/0VDC/-12VDC, or +24VDC/+12VDC/0VDC). All depends on the context of how your using them. Using this method, it is always clear what -12VDC means. Using the other method, who knows?? It could be common/0V or it could actually be a negative voltage from common.

More to the point, if it is the common then why not call it that?

What it boils down to is, I feel the +/- should be used to indicate a reference from common instead of a indication of polarity. If you are using it solely for polarity, then you losing more valuable information for no good reason.

 

[Lancie1]

If you have two 12VDC batteries tied in series, what are you going to label the wires?

On a wiring schematic, I would label them +12, 0, and -12 volts. On a wiring connection diagram, I might label them +12VDC, 0 DC, and -12VDC, just as similarly if I had an ungrounded 24 volt power supply, I would label that +24 and -24.

Just because a leg is grounded does not necessarily make that leg a "COMMON". It only makes it a grounded leg. Often the grounded leg is used as a commom, but not always.

Thinking that there is any convention or rule-of-thumb in electrical circuits that you can assume to always be true only proves that you are not yet old enough to have found out differently.

 

[DamianInRochester]

Just because a leg is grounded does not necessarily make that leg a "COMMON".

Please point to where I said this?

But I will say that I think it is very poor practice when you have your system grounded that you do not call it out in regards to it relation to ground. For the same reason I think it is poor practice to feed power to the bottom of contactors or fuses or use the shield as a current carrying conductor or other goofy things that are not explicity against code but are unintuitive.

Unless I have a very good reason to float a power supply I always tie the low or center leg to ground. This way I have predictable behavior for the fusing when there is a short circuit to ground or some other potential. Is it required? No of course not.

Please tell me what the negative is about my method?

Here is a negative for yours.

I have a panel with a 12VDC power supply for some analog circuitry that someone built a few years ago. They want to update a transducer and use a bipolar version that now requires a +/- 12VDC supply. Well, the guy who did the previous design liked your method of labeling wires, so 0v was actually labeled -12V. So now after I replace the single power supply that is in there with the new bi-polar supply, what am I going to label my actual-12VDC? Had the guy went with ANA-com or 0vdc etc, no problem. Now I either have a confusing mess or I need to make a bunch of new tags. In reality, provided the panel space is there I will probably just leave the old power supply on and put the new one on for just this purpose and label the leads something completely different.

Thinking that there is any convention or rule-of-thumb in electrical circuits that you can assume to always be true only proves that you are not yet old enough to have found out differently.

It really dissapoints me when someone resorts to using the age card and putting words in other peoples mouths to try and argue their points. I never said anything about "rules of thumb" or "can assume to always be true". I pointed out the negatives of doing it that way and why I don't like it. I didn't even say it was wrong, but only that I detest when it is done that way. I think if there is a better way, then why would you not use it?

I will tell you the same thing that I tell everyone else that has ever tried to use the age card with me to settle an argument. Just because you have been doing it that way for several decades doesn't make it right. I've seen a lot of people do a lot of dumb things for a very long time and swear by their success.

I'm old enough to understand that much!

 

[bce123]

put the new one on for just this purpose and label the leads something completely different.

How about ps2 24v+ and ps2 com and ps2 24v- . I have panels that often have more than 1 power supply

 

[OkiePC]

How about getting the wire number from the sheet/line number of the drawings? If there are 200 pages of drawings and I find a wire labeled "+24VDC" how do I find where it originates in the drawings?

 

[Saffa]

It's horses for courses. Sure, if you've got a set of drawings for an entire plant with 10 different 24V power supplies then label them differently according to sheet/line number. However if it's a tiny little panel with only one PSU then I normally wouldn't. Yes, sometimes later additions can add to the confusion, but as long as your labeling method is consistent I think that's the most important - whether you called it +24V or BANANAS, as long as I can trace it from one end to another and can identify when wires should not be connected together (i.e. 0V and 0V2 being two different commons maybe?), you've done your job.

90% of the breakdowns I have to fault find are in panels that are 20+ years old, where the drawings were done on parchment and lost by 3 successive Works departments. The easiest ones to work through are the ones with simple, 3-4 character/number wiring number schemes.

 

[GeoffC]

AS far as wire numbering goes. Today we are not restricted to numbers so I actually prefer a scheme using device id.function
eg pump 1 estop circuit would be PMP1.ES1 on the drawing index I would include the device id and in plc code the tag would be of a similar format
This system allows for easier modifications, systems that use page numbers really fall down when modifications are carried out and drawings are redrawn. Other systems that use plc io addresses as wire numbers are ok until the plc is changed, field wiring normally lasts a lot longer than a plc system, when the plc is updated all the io addresses could change.