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 Post subject: Labeling Motor Control Centers
PostPosted: Fri Oct 01, 2021 6:48 am 

Joined: Mon Mar 09, 2020 9:27 am
Posts: 18
We have come to the conclusion that we would like to have an arc flash sticker on each bucket of our MCC's. Is anyone else doing this? Is there a simple way to have SKM create the label for each bucket that will have the same IE and information as the main, but with the name of that individual bucket?
The only way i can think is to add a cable of the largest size and shortest distance possible from the main MCC bus to another bus, then the breaker for that bucket.

What are your thoughts?


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 Post subject: Re: Labeling Motor Control Centers
PostPosted: Fri Oct 01, 2021 8:03 am 
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Joined: Mon Jan 18, 2010 11:35 am
Posts: 550
Location: Wisconsin
aguywithfeet wrote:
We have come to the conclusion that we would like to have an arc flash sticker on each bucket of our MCC's.


Why do you think that?
How does the incident energy change from one bucket to the next? 7.99 calories/cm^2 is not really different than 5.1 calories, when it comes to selecting PPE.

The company I used to work for, determined the worst case for any bucket in any MCC section, and used that value for the entire MCC (except the incoming section). We placed one label per section, usually on the vertical wireway door, although sometimes it was every third or fourth section.


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 Post subject: Re: Labeling Motor Control Centers
PostPosted: Fri Oct 01, 2021 10:33 am 

Joined: Mon Mar 09, 2020 9:27 am
Posts: 18
We want to show that that bucket was included in our study. We are using the line side of the MCC Main OCP for each bucket. We've had people use the excuse that they thought the bucket they were in was not the IE that was on the main compartment. So this will eliminate that argument.

Just need to know how to have the software create a sticker for each bucket. When i do as i said about the copper bus of 5000 kCM and 25 parrelel runs, it cuts my IE in half on the test study i'm doing.


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 Post subject: Re: Labeling Motor Control Centers
PostPosted: Mon Oct 04, 2021 4:42 am 
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Joined: Wed May 07, 2008 5:00 pm
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Location: Rutland, VT
I would say that it is more of a training and awareness issue that if it is understood that the one label on an MCC applies to the entire MCC, including individual buckets, you are better off. Too many labels can be distracting.

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 Post subject: Re: Labeling Motor Control Centers
PostPosted: Mon Oct 04, 2021 8:03 am 
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Joined: Tue Oct 26, 2010 5:00 pm
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Location: Maple Valley, WA.
As stated previously, individual labels for each MCC bucket is not recommended. This is because the line side of the MCP (bucket breaker or fuse,) is only slightly less than the main bus of the MCC. The cubicle dimensions will only change the value a bit....not a lot. One way to compromise is to create copies of the MCC main bus label and put that on the front of each cubicle. However, I too feel that this is more of a training issue. The electricians need to be trained on how to interpret the AF labels.

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 Post subject: Re: Labeling Motor Control Centers
PostPosted: Mon Oct 04, 2021 8:34 am 
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The only time we apply multiple labels to an MCC is if there is a Main Circuit Breaker, then we post the lineside and the loadside IE's on the MCB unit.
If the MCB has an ARMS, then the loadside gets 2 AF Labels - one for ARMS ON, one for ARMS OFF. The loadside of the main applies to the entire MCC, even if multiple lineups. If a MLO has an upstream ARMS device, it gets one for ARMS ON, and one for ARMS OFF. Either way, MLO/MCB-loadside, AF label(s) apply to the entire MCC. We have done MCC's with literally hundreds of buckets. Definitely a Training Issue.

I have seen AF labeling by others that only shows the BEST CASE (ARMS ON) IE on the AF label, but I would not recommend that approach.


Ed Robinson, P.E.


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 Post subject: Re: Labeling Motor Control Centers
PostPosted: Mon Oct 04, 2021 9:22 am 
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Joined: Tue Jan 19, 2010 2:35 pm
Posts: 154
I can't tell you if marking each bucket is a good idea or not, but can tell you our policy. That's to label logically. For example labeling the individual sections of a MCC may be enough to properly notify the worker of the hazards. We've found there are often too many labels on most MCC's. Adding more labels on each bucket leads to "label overload" meaning, there are so many labels people don't read any of them. More over, the AFH for a standard MCC is pretty much the same all the way through the MCC. Our feeling is the labeling needs to be reasonable. Not too many and not too few, but just enough so a reasonable worker is properly notified of the arc flash and voltage hazards. We've found that in older facilities, facilities where there has been turn over of the maintenance crews, the labeling is not only confusing or wrong, but dangerous. In one case, the switchgear was correctly labeled on the back side, and mislabeled on the front side. In another case, a main breaker had 9 different labels on the door. Talk about confusing. I suggest you approach this with the idea to make it easy and clear so the worker knows the hazards. D that and you'll likely get good results.


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 Post subject: Re: Labeling Motor Control Centers
PostPosted: Tue Oct 05, 2021 3:17 am 

Joined: Mon Mar 09, 2020 9:27 am
Posts: 18
Thanks for the replies.

A typical MCC i deal with has a main breaker compartment 1200A -3000A, and then 8-24 buckets in 3-5 sections. We have had the comment that when they see a sticker on a section panel, they assume that sticker applies to only that panel and what's behind it. i believe it is more of a cop out and i agree training and policy implementation need to be addressed. Unfortunately that's out of my hands, but we are working on it. Some of the people tasked with verifying absence of voltages in these things are more of an electronics background and other than the annual training they receive on Arc Flash here, have never thought about it before.

All that being said, I am asking more about the nuts and bolts of the SKM software and how to make a label for multiple buckets with the same IE as the line side of the main breaker and that will have the name of that individual bucket. Until now we have been making 10 copies and then going in to Adobe PDF and changing the name on 9 of them to the bucket name.


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 Post subject: Re: Labeling Motor Control Centers
PostPosted: Thu Oct 07, 2021 5:51 am 
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Location: Rutland, VT
Terawatt wrote:
The only time we apply multiple labels to an MCC is if there is a Main Circuit Breaker, then we post the lineside and the loadside IE's on the MCB unit.
If the MCB has an ARMS, then the loadside gets 2 AF Labels - one for ARMS ON, one for ARMS OFF. The loadside of the main applies to the entire MCC, even if multiple lineups. If a MLO has an upstream ARMS device, it gets one for ARMS ON, and one for ARMS OFF. Either way, MLO/MCB-loadside, AF label(s) apply to the entire MCC. We have done MCC's with literally hundreds of buckets. Definitely a Training Issue.

I have seen AF labeling by others that only shows the BEST CASE (ARMS ON) IE on the AF label, but I would not recommend that approach.


Ed Robinson, P.E.


I would have to disagree with this as unless the MCC is a tested configuration to prevent an arc fault from engulfing the main breaker, the only legitimate incident energy value is the one that ignores the main breaker. I believe what you are stating could lead to personnel wearing less than adequate PPE for what the real incident energy value is.

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 Post subject: Re: Labeling Motor Control Centers
PostPosted: Mon Oct 25, 2021 10:46 am 
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Joined: Sat Apr 04, 2009 9:50 pm
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Location: San Antonio, TX
I would not place two labels on MCCs, or on any equipment with a main OCPD. Many people argue the idea of placing a line-side and a load-side label for equipment with a main OCPD. I would not do that UNLESS I can proof proper segregation of the incoming line-side section from the feeder sections of the equipment. IEEE 1584.1 2013 is very clear on this. Proof of segregation would be a written communication by the manufacturer of the equipment (good luck if you get it) or a successful test of ANSI C37.20.7 with a Sufficient C additional test for compartment integrity. You can not know if the line-side arc flash energy will break thru the barrier (if there is one) and migrate to the adjacent section if it is not tested. If you can, please let me know how.

Just think what would happen to a worker using a low value of arc-rating PPE (determined by the load side IE) when a much higher AFIE arc flash event breaks through the untested barrier exposing the worker to a much higher AFIE.


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