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 Post subject: Overdutied Equipment Label Language
PostPosted: Fri May 22, 2015 9:28 am 
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Joined: Wed May 07, 2008 5:00 pm
Posts: 855
Location: Rutland, VT
I am working on a label to be applied on equipment that is overdutied. This would most likely be a panelboard containing breakers inadequate for short circuit level or a piece of equipment such as power factor correction equipment.

The wording I am considering is:

This equipment has been determined to be overdutied and a risk to personnel.

Operation and/or work on this equipment is Prohibited.

I would appreciate any comments or alternative wording.

Thank you in advance.

Barry Donovan, P.E.

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 Post subject: Re: Overdutied Equipment Label Language
PostPosted: Tue May 26, 2015 7:58 am 
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Joined: Tue Jan 19, 2010 2:35 pm
Posts: 152
If we label, we only label with danger labels. We state in the report that the equipment is under rated and could fail if called on to interrupt a fault - that the equipment and calculations cannot be relied on until after the corrections are made. Once the corrections are made, we return and install the labels. We'll state in the report that this underrated device can present a real danger to personnel and equipment.

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 Post subject: Re: Overdutied Equipment Label Language
PostPosted: Tue May 26, 2015 8:05 am 

Joined: Mon Jun 09, 2014 9:19 am
Posts: 43
We do not allow our technicians to operate such equipment. We do not put the arc flash label on the equipment from the report, but do place a danger label that states not to operate the equipment energized. As part of the training the field techs get after the reports are finished, they are told about the dangers that exist with that equipment and are given options on how to de-energize safely before servicing. Our company has been replacing any equipment or upstream overprotective devices to lower the energies to make it safer for our techs.

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 Post subject: Re: Overdutied Equipment Label Language
PostPosted: Tue May 26, 2015 8:26 am 

Joined: Sat Aug 22, 2009 12:39 am
Posts: 5
Unfortunately, I'm convinced that there is NO WORDING appropriate for an Overdutied Equipment Label. This equipment should not be there in the first place. In order for the label to be compliant with ANSI Z535.4-2011, it must have a minimum safe viewing distance. That is defined as the closest distance a person can be to a safey sign and still have time to follow the safety sign's message to avoid the hazard (hazardous avoidance reaction time). This distance determines the proper letter size for the word message on the label. With the realization that at any time, the protective device could be called upon to operate for a downstream fault, if you're reading this, you are too close! Perhaps you are thinking of installing barricades and placing the label at that distance. Great, if you could only determine what distance is "a safe distance" from such an explosion (couple football fields away?). A former chair of 70E once told me that if such a warning sign could be developed (it can't), the only appropriate place for it to be placed would be on the plant manager's desk so that he would be reminded that he is placing his employees and others in danger each day until the equipment is replaced. Arc-flash labels warning of a burn injury should NEVER be placed on overdutied equipment as it makes the equipment appear as safe as all the other equipment in the facility--instead of the greater hazard that it is. Barricade it and replace it, but don't label it so someone stands in front of it reading the label!

Also, watch out for bus faults further down in the system fed from the overdutied equipment that could be large enough to still overduty the upstream device. Calculating the downstream bus' IE using the opening time of the upstream overdutied device is impossible as contacts could weld and never open, so the IE calculation is not obtainable so you can't affix AF labels to the downstream equipment either. Bottom line, no AF results shall be calculated for overdutied equipment (stay completely away from the gear) or equipment downstream of overdutied equipment that causes the upstream protective device to remain overdutied.

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 Post subject: Re: Overdutied Equipment Label Language
PostPosted: Tue May 26, 2015 10:42 am 
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Joined: Mon Jan 18, 2010 11:35 am
Posts: 544
Location: Wisconsin
Let me say it clearly: improperly applied equipment should be replaced.
'Overdutied' usually means the device is not rated for the available bolted fault current at its line side terminals. Most often this phrase is associated with LV equipment, primarily molded case circuit breakers (side note; I don't know why so many studies skip the evaluation of fusible and non-fused disconnects)

Other than as a result of interaction with the wiring, how would the device ever see a bolted fault with the line side current value? The vast majority of fault currents a device sees are arcing through faults, which are typically significantly less than the bolted amount. Do you treat a device that is rated 10kA with an available fault current of 10.5kA the same as one with 22kA available? How about when the company ESWP requires lock out and voltage check at the properly rated MCC bucket, before operating a local disconnect? What about an automatic paralleling Tie breaker that transfers between two live sources for not more than 30 cycles?

Risk analysis is important, failure mode needs to be considered when you are putting 'do not use' labels on someones equipment. Simply providing a label does not absolve you from litigation.

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