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Old January 25th, 2012, 03:55 PM   #1
Mihaylov
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Question Correct Conductor Marking

Hi
I am working for machine manufacturer and I am responsible for electrical diagram designing and PLC & HMI programming. Machine wiring is performed by a subcontractor. He uses a method of wire numbering which seems wrong.

For example, the button (S1) is connected to the PLC input (X10) through two terminals (X1:3) & (X2:5):

(S1)--|5|------|5|--(x2:5)--|5|------|3|--(x1:3)--|3|------|X10|--(X10)

The devices are displayed in ( ), the wire markings are displayed in | |.
- Both ends of the first wire are marked with the terminal number of X2 terminal strip;
- The ends of the middle wire are marked with the terminal number of X2 and X1 terminal strips;
- Last wire is marked with the numbers of connected devices - X1 terminal strip and PLC input name.
What a mess.

I hope that my explanations and 'diagram' are clear.

Are there any standard containing rules for conductors marking in electrical circuits? I know that all wires connecting two devices have to be marked with the same number. Am I right? What is the correct marking?

Best Regards
Mihaylov
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Old January 25th, 2012, 04:12 PM   #2
OkiePC
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Uh, yeah, that is a terrible scheme. Each conductor needs to have it's own wire number throughout...you can't lable one end 3 and the other end 5, and you sure don't want two different circuits to have the same number!

I prefer to use line numbers from the electrical drawing as a prefix or some other way to get you from a wire label to the correct spot on the drawings.
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Old January 25th, 2012, 05:08 PM   #3
James Mcquade
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I agree with Okie.

i use line numbers based on the drawing line number.
for example, sheet 3, line 10. The first wire number will be the power wire number, then 3100, 3101, 3102. On large sets of prints i would use 03 for the page number, 10 for the line number, and 00 to 99 for the line number. i haven't seen prints with more than 10 different wire numbers, but i'm sure there are some.

i have also seen a numbering method called destination wiring.
this method goes like this - device a goes to device b.
at device a, the wire # would be "DEV B" telling you to go to device b. at device b, the wire # would be "DEV A" telling you to goto device a. its hard to get used to, but its another way of numbering wires.

regards,
james
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Old January 25th, 2012, 07:27 PM   #4
iant
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it looks like his intention was to have another device in series with S1
that is why you have an extra terminal - (I am assuming these terminals are in the same panel)
the idea of going from 5 - 3 is wrong - you would normally
call it a jumper or bridge and mention the numbers
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Old January 25th, 2012, 07:55 PM   #5
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I've encountered the wire marking system where each end was marked by terminal ID end point just once in a machine imported from Sweden. If the wire comes loose its easy to see where to re-land it without referring to the drawing. That's the only advantage I can think of. Since that doesn't happen very often its not much of an advantage.

It doesn't help panel construction, it might make it harder since he has to sort markers.

It makes troubleshooting harder for maintenance techs as they cannot trace a signal without referring back to the drawing for each and every wire segment and it makes them dependent on the accuracy of the drawing.

I think its driven by IEC 61346, but I also don't think it is how IEC 61346 was intended to be applied - I could be wrong about that however so if any IEC 61346 experts are out there I would love to hear their take on it.
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Old January 26th, 2012, 03:28 AM   #6
Mihaylov
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Thank you for the advice.

@iant: The terminal strip X1 and X2 are in different locations. X1 is in electric cabinet where PLC is mounted, X2 is in operator's panel box.

Our subcontractor has more than 30 years experience in system wiring and maybe it is impossible to change his method of wire marking. He says 'You don't know anything' since I began to criticize him. The main problem is that there are differences between electrical drawing and the wiring. Lord help our customer's maintenance team!

I know the marking method you talking about - every wire has an unique name. The method I mentioned above says that every signal has a name no matter how many times the wire is divided into parts by terminals, each wire end is marked with this number. I don't know which method is better.

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Mihaylov
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Old January 26th, 2012, 04:33 AM   #7
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there is no excuse for having one wire with a different number at either end. this is a very bad practice.
there are many other wiring numbering methods -
the Idea of increasing the number after each terminal is one method.
But - the Idea of a different number on the same wire is not good.
I have a prefference on using the actual PLC address.
But have also found that the idea of relating thw wire to dwg page no. then cross reference to the page is an excelent method.
Makes it easier to find the wiring in a drawing
i.e. pg 16 'C' '5' wire nuber 16C05 - easy to find
Component same - switch (s) 16S05
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Old January 26th, 2012, 06:17 AM   #8
Ventax
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He's your SUB-contractor, If he wants to get paid then he should be wiring it to your satisfaction not his, regardles of how much experience he has.
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Old January 26th, 2012, 08:46 AM   #9
James Mcquade
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Mihaylov,

what is the plant's working hours.

i am in maintenance and have some statements for you.
not trying to beat you up or be mean in any way.
just want you to see it from my view.


if the electrical prints do not match the actual wiring numbers, "just how in the world do you expect maintenance to fix it"?

we rely on the electrical schematics to be correct. we know that sometimes errors are made in the wiring as far as numbers, errors are sometimes made in the prints. people make mistakes, and generally maintenance figures out the wiring problem.

What you will be asking your maintenance to do is create a new
set of schematics just so we can trouble shoot the machine!

how much downtime can you afford when the machine goes down the first time? and are you available 24/7 to help us work on the machine while its down?

remember,
a machine can be made of pure gold and cost a billion dollars,
but its not worth 10 cents if maintenance cannot trouble shoot the plc program and wiring in order to get the machine running when its down. the first thing we will do is call you! day or night, we will call!

consider the small snowball rolling down the hill.
machine downtime costs production, loss of production gets the attention of program managers, program managers report to management, management reports to ???, they yell at your boss who in turn YELLS AT YOU. this time that little snowball is 20 ft in diameter and i hope you get the point.

regards,
james
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Old January 26th, 2012, 11:29 AM   #10
Timbert
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Quote:
Originally Posted by TConnolly View Post
If the wire comes loose its easy to see where to re-land it without referring to the drawing. That's the only advantage I can think of.
We had some electricians at my last job that wanted the wires numbered like this because, as you said, when they come loose they would know where they go without looking at a drawing. If wires falling off machines is happening regularly, you need better assembly techniques and/or parts not an oddball numbering scheme.

Quote:
Originally Posted by Mihaylov View Post
Our subcontractor has more than 30 years experience in system wiring and maybe it is impossible to change his method of wire marking.
I'm sorry but I got decades of experience too; frankly, I think the guy is an idiot.

As a panel assembler, such a scheme would allow you to have unskilled labor that simply connects the ends of each piece of copper.

As a designer or maintenance worker, such as scheme will force each connection to be traced through all the intermediary connections to find the destination. Which is complicated, error-prone, and time consuming.

Quote:
Originally Posted by Mihaylov View Post
He says 'You don't know anything' since I began to criticize him.
Is there really the kind of person you want to be working with anyway? He should have been able to rationally persuade you that his method was better, rather than try to bully you. He works for you, not the other way around.
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Old January 26th, 2012, 03:33 PM   #11
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I've worked on a couple of recent panels where the wire had the component terminal ID but they also had a signal number (printed labels). For me, the advantage comes when changing a component with a number of wires attached. An example is a contactor with add-on blocks.
Paul
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Old January 26th, 2012, 03:51 PM   #12
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Quote:
Originally Posted by Mihaylov View Post

(S1)--|5|
This should be numbered 3 or 4 for a NO contact, 1 or 2 for NC contact. Using 5 is crossing over two different ways of wiring numbers, both of which have advantages / disadvantages

Who wants to waste time putting on numbers anyway :o)

Last edited by Marshy; January 26th, 2012 at 03:56 PM.
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Old January 26th, 2012, 04:45 PM   #13
Lancie1
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Quote:
Our subcontractor has more than 30 years experience in system wiring and maybe it is impossible to change his method of wire marking.
I have over 40 years experience in system wiring, designing wiring, connecting wiring, and troubleshooting wiring.

Having different numbers at different places on a wire is a horrible method. It is not impossible to change his method, but it will costly for him to go back and fix wire numbers for systems already installed. Tell him you will make a note of this to remember for the next job.
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Old January 26th, 2012, 05:03 PM   #14
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We have a site standard for all PLC code written, such as AOI's and mapping I/O etc... I even issue a lot of AOI's to contractors and say that they must use them in their PLC code.

We also have site standards for all of our wiring. When we put a job out for tender these standards are given to every contractor.

If the contractor ever came back and said they don't do things that way, then I just simply wave goodbye.

Admittedly some contractors will come back and say that it might cost a little more to do it our way, but sometimes that little extra cost is well worth it just to keep everything the same.

IMHO a contractor is there to do as you instruct them, that is what you are paying for. In my job, if things go wrong it's me that gets the verbal beating, and although I pass that down to the contractor, it was still my responsibility.

So in short you are paying HIM to do things the way YOU want them done. If he can't accept that, then I would get myself a different contractor.

Mark
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Old January 26th, 2012, 05:35 PM   #15
Mihaylov
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Quote:
Originally Posted by James Mcquade View Post
how much downtime can you afford when the machine goes down the first time? and are you available 24/7 to help us work on the machine while its down?
...
The first thing we will do is call you! day or night, we will call!
I participate in the commissioning of the machines in our customer's plants so I am aware of maintenance difficulties. My goal is to make the best possible documentation to be easier for colleagues in the plants. Therefore I try to change the method of wire marking.
Typically, we provide support 2-3 days after failure, I am glad that nobody calls me personally, they first speak with my boss.

Quote:
Originally Posted by Timbert View Post
He works for you, not the other way around.
He is old friend of my boss. I am just an employee trying to do my job.

Quote:
Originally Posted by Lancie1 View Post
Having different numbers at different places on a wire is a horrible method.
Thank you all for the advice. You gave me courage to insist on change the way this job is done. You are right, He is a idiot.
We are in war. I wil try to force him to do the correct wiriring. If he refuses then there will be a long conversation with The Boss.
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