MCC Numbering Convention Question

[Voltrael]

This may be a fairly trivial question, but I am trying to ensure that things are being done uniformly and to applicable or industry standards.

My question is about labeling of numbering designations for motor control center cubicles (buckets). From my understanding, for example, the top starter in the first vertical section of an MCC would be designated 1A. If that starter was two units high, the next bucket would be labeled 1C, and so on. Labels would typically go from A to M, with I being skipped.

I recently starter working for a new company at an existing paper mill. What I have found there is that they have decided to use the bottom of each cubicle for the designation. From my example above, the top starter would be labeled 1B, and the next would be 1D, assuming it was two units high.

My question is, is there a single standard in industry, and if so, what is it? What convention are others currently using?

 

[templdl]

I am not aware of any standard one know what is customary. When you deviate from what is customers then you are in so much speaking a different language. If you are in a facility and learn the language used there and become accustomed to it there should be no issues. The difficulties become relavent when attempting to communicate with the rest of the industry that identifies MCC buckets on a customers fashion of those people who are new to your facility learning a new language so to speak.

 

[Voltrael]

There is a plant standard, but it is not widely used, and we will be replacing a large percentage of MCC's in the next few years, so now would be the time for me to revise the standard, if that is warranted.

Thank you.

 

[templdl]

There is a plant standard, but it is not widely used, and we will be replacing a large percentage of MCC's in the next few years, so now would be the time for me to revise the standard, if that is warranted.

Thank you.

Cool. It provide you with the opportunity to bring you plant up to the commonly a?cepted identification methids.
It could be similar to the english language being universally accepted as the spoken language but a specific plant standardized of Spanish which is OK should everybody in the plant speak Spanish. But when some who doesn't speak Spanish starts to work in the plant now he has to learn to speak Spanish. It may be like assuring that everyone is on the same page which is often made more difficult when a plant uses nomenclature that is different than that which is commonly used.
When ordering a new MCC you could specifically have the manufacturer label the buckets in the custom manor that you specify which works against what is customarily done. But in doing so you would perpetuate the issue.

 

[don_resqcapt19]

As long as the bucket numbering in the plant is all the same, I see no reason not to continue that same marking. That assumes that the documentation and the bucket markings match.

If you do decide to change, I would make sure that all of the existing markings and documents are changed at the same time.

Making the change could be confusing to existing employees. They will have to be trained to make sure that the correct equipment is locked out when the need to do a lockout occurs. If they go to the new documentation, and look up the cubicle, I would not be surprised if the lockout out would be made based on their previous knowledge of where bucket 1A is physically located, not where it is based on the re-marking.

 

[petersonra]

Every MCC drawing I have ever seen 1A is top left section, regardless of size.

I have never seen one numbered from the bottom of the bucket.

I don't think it matters much.

 

[GoldDigger]

Every MCC drawing I have ever seen 1A is top left section, regardless of size.

I have never seen one numbered from the bottom up.

I don't think it matters much.

The OP is not talking about numbering from the bottom up, although that was my initial interpretation too.
He is talking about which grid location to use for a section that is more than one unit high.
If the top section fills grid spaces 1A and 1B, should that section be referred to as 1A or as 1B?
In the case of a multi-space multi-pole breaker in a panelboard, we use the smaller number or else list all of them.

 

[petersonra]

The OP is not talking about numbering from the bottom up, although that was my initial interpretation too.
He is talking about which grid location to use for a section that is more than one unit high.
If the top section fills grid spaces 1A and 1B, should that section be referred to as 1A or as 1B?
In the case of a multi-space multi-pole breaker in a panelboard, we use the smaller number or else list all of them.

A poor choice of words on my part. I even went back and edited it when I read it because I thought people might think I thought he was labeling from the bottom section up, rather than the bottom of the bucket. i edited it again.

 

[Jraef]

Confirmed, there is no standard for unit numbering in either UL845 or NEMA ISC-18, the two main standards for MCCs in North America.

The reason I can think of to change it now however is that every MCC mfr that I am aware of is now using a computer generated layout system, which has very specific conventions of numbering and will be based on the convention of the buckets with the location as the topmost space it occupies, based on 12 "half space factors" (6" buckets) in a vertical section. So the top unit in Section 1, regardless of it being one space factor, 3-1/2 space factors or 6 space factors, will be called "1A". If you insist on doing it the old way it was done at your facility, you are just asking for trouble. For example I used to be able to put in any number I wanted to on the old paper based MCC ordering system, nobody cared and they just built it as I showed it. But now, I can no longer do that. The computer based system will automatically number it per the above convention. If I want it numbered any other way on the drawings, i.e. calling a unit by the lowest level unit space it occupies, it will require manual intervention on the part of an engineer.

That's not to say it can't be done, but it means your MCCs become "Engineered Specials" just for that reason alone, subject to longer lead times and more engineering charges. Then if anyone in the future forgets this "special" and does it the way the computer spits it out, you end up with confusion in the field.

Go with the flow man... just go with the flow...

 

[templdl]

Confirmed, there is no standard for unit numbering in either UL845 or NEMA ISC-18, the two main standards for MCCs in North America
That's not to say it can't be done, but it means your MCCs become "Engineered Specials" just for that reason alone, subject to longer lead times and more engineering charges. Then if anyone in the future forgets this "special" and does it the way the computer spits it out, you end up with confusion in the field.
Go with the flow man... just go with the flow...
View attachment 9281

To my point and you gave an excellent explaination. I have taken and entered countless MCC orders. And, yes, you can customize MCC that would be similar to rowing upstream against the current just because of a customized bucket ID system.