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 Post subject: 480V Main Disconnects - CB Operation
PostPosted: Wed Sep 30, 2009 2:03 pm 

Joined: Wed Sep 30, 2009 1:43 pm
Posts: 1
An arc flash analysis has been performed at one of our multiple-story facilities. As a result, many of the 480V disconnects on each floor were labeled with the 'DANGER - ENERGIZED WORK PROHIBITED' labels in accordance with NFPA 70E for components determined to be greater than 40cal.

The maintenance employees responsible for the electrical facilities within the building are now questioning whether they can safely operate the CB disconnect which is located outside the disconnect enclosure. They believe operating a disconnect with doors closed is not considered energized work since no electrical conductors or circuit parts are exposed.

The debate continues to whether operation of the disconnects can still be accomplished without deenergizing the entire building. Does anyone have any thoughts or clear guidance on what should be done in this particular scenario?


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PostPosted: Wed Sep 30, 2009 3:48 pm 
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
WJMan wrote:
An arc flash analysis has been performed at one of our multiple-story facilities. As a result, many of the 480V disconnects on each floor were labeled with the 'DANGER - ENERGIZED WORK PROHIBITED' labels in accordance with NFPA 70E for components determined to be greater than 40cal.

The maintenance employees responsible for the electrical facilities within the building are now questioning whether they can safely operate the CB disconnect which is located outside the disconnect enclosure. They believe operating a disconnect with doors closed is not considered energized work since no electrical conductors or circuit parts are exposed.

They are wrong, unless you have arc rated switchgear operation and/or racking of breakers with the doors closed is considered energized work per the 70E, they use the phrase "interaction with equipment" in the definition and cite the task tables as examples.

WJMan wrote:
The debate continues to whether operation of the disconnects can still be accomplished without deenergizing the entire building. Does anyone have any thoughts or clear guidance on what should be done in this particular scenario?


They can use remote operators to operate them from outside the arc flash boundary. That what most facilities are starting to do.


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PostPosted: Thu Oct 01, 2009 6:53 am 
Sparks Level

Joined: Wed Sep 23, 2009 9:29 pm
Posts: 83
Location: Western Canada
Hazards over 40 cal

Hello Zog
Remote racking is a great way to remove the risk when racking but I am struggling with the Test portion of lockout. Testing will require the electrician to interact with the gear and be exposed to the potential arc hazard. any thoughts on how to deal with a +100 cal hazard when testing? Am I thinking about this all wrong??


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PostPosted: Thu Oct 01, 2009 7:07 am 
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Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
Canuck01 wrote:
Hello Zog
Remote racking is a great way to remove the risk when racking but I am struggling with the Test portion of lockout. Testing will require the electrician to interact with the gear and be exposed to the potential arc hazard. any thoughts on how to deal with a +100 cal hazard when testing? Am I thinking about this all wrong??


Good discussion on the testing part here. http://www.arcflashforum.com/showthread.php?t=673


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