# NFPA 70E Is ARC Flash Gear Required When Working In A MCC Bucket



## Fourdigger (Mar 11, 2021)

Hello I am curious if ARC Flash gear is required when working in a bucket when it is switched off. Granted there is still 480VAC on the top of a breaker but not the bottom when switched off. We sometimes have to replace a motor starter or VFD. All the tests and repairs are done deenergized so does that constitute the need of gear?


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## mayanees (Jan 12, 2009)

Yes, when you cross the restricted approach boundary, which for under 1000 Volts is 12 inches. And for any tasks covered under 130.5(C), Estimate of likelihood of Occurrence of an Arc Flash, 70E 2021.


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## SWDweller (Dec 9, 2020)

Off is not de-energized . You state line side hot. If there is power in the bucket anywhere you need to be protected. Removal and re install a bucket into LIVE buss is also a Arc flash situation.
Removal I might do, reinstall not any more.
Has your facility done an arc flash study? The stickers of compliance should be on every electrical piece of equipment. They will tell you what you need to be wearing.


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## FarmerEngineer (Mar 18, 2021)

Mcc buckets were designed to swap out, not repair while inserted. 

Suit up and swap the bucket.


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## brian john (Mar 11, 2007)

FarmerEngineer said:


> Mcc buckets were designed to swap out, not repair while inserted.
> 
> Suit up and swap the bucket.


I have been to 5 maybe 6 jobs where an electrician was burnt, flashed, or both swapping MCC buckets. If there is an issue with the bucket IMO you should not swap it hot. Heck, I would not swap a new MCC bucket with a new bucket.


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## paulengr (Oct 8, 2017)

I have seen some old Square D MCC's that had a clever system where there was a disconnect switch that pulled the breaker stabs off the bus before you actually racked the bucket in/out. It's old but SO much safer.

MCC buckets were made for easy removal and insertion, very true. However, NO MCC VENDOR actually documents that it is acceptable to do ENERGIZED insertion and removal. All tell you to de-energize first. Lots of people have been burned pretty badly doing this. For one thing one of the big gotchas is that often the arc is propelled down the the end of the bus bars and then blows out through the bottom at your feet, not at the work site. In the main compartment frequently they've been known to jump to the line side of the breaker.

But this is an area where basically 70E sucks because the people on the Committee have never actually serviced equipment, energized or not, in their lives. Even very old equipment generally meets the definition of "not exposed". The biggest hazard is that often control wiring on the door itself can bite you if you brush up against it. Hanging a rubber blanket over it takes care of this. Once inside though with the breaker or disconnect open none of the power conductors are energized from the bottom of this unit and the top almost always qualifieis as "not exposed". The definition of "arc flash hazard" (see defintiions) is that you do something that is LIKELY to cause an arc flash. So it's one thing to go probing around the top of the breaker with a non-insulated screw driver but otherwise according to 70E, no "arc flash hazard". The second side is that with ANY starter you need to be aware of the fact that actually de-energizing everything is not so trivial. It can have common control power which is sort of hard to disable. But even with a control power transformer per bucket, you've still got an issue. A PLC for instance will run power of some sort through the aux contact of the contactor and back to the PLC. So unless you go pulling control fuses (if any) there is no way to truly isolate control power in a bucket. And if you do, your chances of finding and disabling everything isn't very good. So control power in particular is nearly always potentially energized, no way around it. 70E says no problem...just glove up and do everything in rubber gloves. That is of course unrealistic and impractical.

Stepping back a bit 70E references an IEEE standard for actual work practices. That document clearly gives 3 different work methods: insulated tools, insulated gloves, and live-line/bare hands. Now using an insulated tool like a multimeter or an insulated screwdriver and/or insulated pliers is VERY practical and the way that we always did things before 70E. This is an area that the Committee is completely out to lunch on. Notice that most of the committee members work for companies like Oberon. They have no idea what they are doing and are there only to sell PPE. Realistically of course we know that a pair of dry leather gloves is just fine for 120 V work. The amount of air gap needed to prevent a shock is less than 1 mm. But the test for insulated gloves is to fill them with water, dip them in a water tank, and hi pot them. Obviously that won't work on dry leather gloves. 70E recognizes this fact which is why they recommend dry leather gloves for plugging things in. They at least used to just say "avoid contact" in the shock section. Yet they deleted those very practical and sensible things and replaced it with a bunch of self-serving crap. Hence most companies have to enact their own rules overriding this garbage. That was also int he days of HRC "2*" and where it was perfectly fine to wear lower level PPE based on the activity you were doing but you had to go crazy to HRC 4 for other activities. The hazard wasn't changing, only the likelihood. Today at least it now says that either you need PPE or you don't, and when you do, the level doesn't change. Somewhere along the way they dropped all reference to insulated tools though because they definitely did NOT want to encourage you to use a multimeter with insulated probes to do legitimate controls work.


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## MES Consulting Group (Mar 22, 2021)

ALL,
very good points ! Note that 70E is a conciseness document, it was never adopted by OSHA. In the USA, OSHA is the LAW that you MUST follow, not 70 E. The real question is, what's the scope, are you "working" under OSHA 1910 General Industry or 1926 Construction. You are permitted (yet very narrow) under 1910 to work "LIVE" donning the proper PPE to "verify the absence of voltage" a required step under OSHA electrical LO/TO, adjust, diagnose and troubleshoot under the 1910. 

However, OSHA 1926 Construction is very clear about "LIVE WORK" if your working on, enhancing, adding value, replacing, modifying, tightening, using a tool (other than stated in 1910) its construction...!!!!!! *NO LIVE WORK IS PERMITTED. *

The one exception to working live is when a systems is de-energize it will endanger or cause more harm.. example ....where turning off ventilation systems will lead to or could lead to.....an explosion, mines, hazardous dust, hazardous storage & manufacturing. To be clear _The word INFEASIBLE in no way shape or form means ITS TOO COSTLY TO SHUTDOWN. 
If your thinking this, the Lawyer will have a question for you
1- how much value is a human life worth vs. production
2- would you let your son or daughter work on it LIVE _

In the simplest terms No one will ever receive an NFPA 70E Citation in the US. (not true in Canada)

Did someone mention Listing and Labeling........ in general terms, UL testing on device's like breakers, motor control those component are inserted "de-energized" as part of the scope of testing its not being tested as its inserted and therefore has no Listing. The manufacture is asking UL to test his/her equipment in a specific way. Changing any component including hot swapping battery in UPS system is a Code violation 70. unbless its listed and labeled to be used that way. 

May seem like its small item but that will be the Insurance companies way out of not paying. 

Please visit me at *MES Consulting Group Inc*.


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