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 Post subject: Replacing Breaker in 480V Panel
PostPosted: Thu Apr 30, 2015 12:43 pm 

Joined: Thu Apr 30, 2015 12:19 pm
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I have a project to replace a branch breaker in a 480V panel. We have opened the main breaker at the panel. However, the site electricians still considers it live work, because there is 480V cable still energized in the panel to the line side of the main breaker. The branch breaker would be connected to a dead bus. There is no exposed 480V. The branch breaker replacement does not interact with any live components.

Similarly I need to connect 120VAC control wiring to a 480V MCC starter. The starter bucket disconnect is opened. Same situation, the site electricians claim that since the bucket is connected to a live bus on the line side of the disconnect this is considered live work.

What's the call? Level of PPE required? Is this considered live work under 70E?


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 Post subject: Re: Replacing Breaker in 480V Panel
PostPosted: Fri May 01, 2015 7:50 am 
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Location: North Carolina
As a default knee jerk reaction, electricians are potentially correct.

First, if you haven't tested it for absence of voltage, it's live. So I have to assume you're following Article 120 for LOTO. That's also a key there...have to be able to LOCK out the circuit breaker. It is now required under OSHA but older equipment may not have this capability and when you order it, MCC's are required to have this capability at least under NEMA. A newer requirement under NFPA 79 requires the disconnect to be lockable INDEPENDENT of the door opening. Older rotary-style disconnects can't do this and this is also the most common configuration for IEC rated equipment. Some older equipment and those with the long shafts projecting through the door with the rotary types can't be locked out without removing the mechanism and installing something else on top of the breaker. With just regular panelboards if the breaker doesn't have provisions for it there are lots of aftermarket lockout devices. Try using it firs tbecause a lot of them don't exactly secure the handle from being operated and are more for appearances than actual functionality.

So this gets us past this point. Now we go on to what the definition of "exposed" is. Exposed means NOT insulated, guarded, or isolated. When you have a breaker staring you in the face, the lugs are generally recessed and if the wiring is stripped properly, very little is exposed above the lug. The test here is whether or not you can inadvertently come into contact with it, not purposely taking a screwdriver and making an intentional effort to be killed. If properly terminated (stripped) in the first place, everything will be GUARDED but not necessarily isolated or insulated. If you need an absolute guide as to this, IEC's "finger safe" guide is just about the most extreme definiition for guarded.

Now keep in mind that exposed applies to both fingers and tools. So if we're working out in the open no problem. But there are two additional pesky issues to watch out for. If dropped tools or parts could roll into the wrong places in the equipment, and there are reported cases of this in the OSHA logs, then that's also "exposed". And for the same reason, fishing (poking wires into a blind opening) where the opening is energized also violates the "exposed" rule. So if the screws that are being used to mount equipment or even a drill used to make the hole (and drill shavings) could cause an arc, it's an "exposed" issue.

Even if there are exposed live parts then as long as you are outside the restricted approach boundary which is "avoid contact" for 120 V and 1 foot for 480-600 V, the "exposed" concern disappears anyways. But since you are talking about work inside an MCC bucket unless its size 3 or larger and you are on the bottom of the bucket, I'll assume this doesn't apply.

If we've established that there are no EXPOSED conductors then under the current NFPA 70E (2015 or even 2012), the second requirement is that by definition, no "interacting with the equipment in such a manner that could cause an electric arc". The 2015 edition contains a table of tasks that qualify but you can do your own risk assessment as welll. Suffice to say that adding/removing buckets is definitely live work but the exception to 130.1 applies since you are only doing this to establish a safe work condition in the first place. Otherwise, again it depends on the task. If connections are removed/made from the load side of a locked out breaker, it's not energized work.

Keep in mind with all of this what the point of the whole "EEWP" permit is all about. It's an administrative procedure to keep electricians from just going in and working live every single time even when they don't have to do it. It is not an absolute, iron clad prohibition on doing any live work whatsoever. It's to make sure that management buys into making a decision on whether or not it reall yhas to be done while energized and that there are good reasons for doing it. And there is an OSHA letter of interpretation that makes it iron clad clear that "continuous industrial processes" does not mean "chemical plants", and that loss of production is NOT in itself a valid reason.

There are also exceptions for doing diagnostic work. Use them. They are there for a reason. You can't really test for voltage (or for that matter following LOTO, testing for absence of volage) without working on energized equipment. Similarly, a lot of online PM's such as PD testing, IR testing, and UV testing, CANNOT be done while de-energized. And you need those PM's to ensure that the equipment is properly maintained. So you can't really prohibit live work in those cases because not doing proper PM's is far less safe than doing them.

Finally, 70E (and OSHA) does not preclude the use of an annual EEWP where you categorically sign off on some types of work. The most common one is for 120 V control wiring with the 480 V side of an MCC bucket locked out where common control wiring is used. The justification is that the possibility of an arc flash is almost nil and we've only got shock to deal with and that shock protection would be used. Operating the larger upstream breaker entails a greater hazard compared to what is effectively a minimal hazard. There are various other variants on this type of argument of recognizing that the hazard is minimal, again depending on the work that is being done. This takes some thought and soul searching for the site and I highly recommend making sure that the site safety management and production management sign off on it too so their necks are on the line. From an electrical point of view working in the dark with a flashlight is not the end of the world and the parties that don't want to de-energize are not electrical.

PPE may also be a second consideration. Just because an EEWP is not required doesn't mean that there is no shock or arc flash hazard. So when working llive and doing work where there is a risk of an arc flash or shock, wear the proper PPE. And whatever you do, don't overdo it either. The stuff is heavy, hot, sticky, and kills both dexterity and visibility. Using PPE when it is not necessary increases hazards. Using too much PPE such as a 40 cal/cm^2 arc flash suit with roughly 30-50% light transmission with an off color and class 2 gloves on a hot summer day inside an electrical room while trying to turn a screw on a #16 wire with a small jeweler's type screwdriver is clearly going to increase the likelihood of dropped tools or parts, misidentification of wires, possible heat exhaustion/stroke, etc.


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