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 Post subject: Obtaining Electrical Device Information
PostPosted: Wed Feb 26, 2014 12:02 pm 

Joined: Fri May 10, 2013 5:40 am
Posts: 3
Hi there.

As an engineer for a consulting firm, we have started conducting arc flash studies for existing healtcare facilities. More often than not I find the need to open switches or covers of equipment (600V or less) to retrieve fuse or circuit breaker information as no existing information exists. When opening these devices energized with no intent to work on them just get the fuse information or circuit breaker trip settings, can I allow the escorting electrician open the cover for me to take down the information or should I let the electrician fully perform this work wearing PPE determined by the NFPA 70E HRC tables? Keep in mind no labels exist on any equipment within the facility. I do not see this as a high risk event, but I would like to get the opinions of this forum. Thank you and I apologize if there is already a thread related to this question.


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PostPosted: Wed Feb 26, 2014 12:23 pm 
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Joined: Tue Nov 12, 2013 6:31 am
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Location: Port Huron, Michigan
Generally should wear a face shield with balaclava, rated gloves, and 8 cal shirt and pants to do this job.


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PostPosted: Wed Feb 26, 2014 3:43 pm 
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Location: North Carolina
Choice #1: Go with nothing. I have recently completed a survey of OSHA cataloged data from 2007 to 2011. I was not able to find any incidents in that 5 year period investigated by OSHA where an arc flash occurred while opening a hinged panel. If it's bolted though, that's a horse of a different color with more than one incident per year on average. The trouble here is that you don't know the condition of the equipment either, so you are playing with fire.
Choice #2: Go with the tables in 70E. That's what I instruct my guys to do, and what I personally do, if we have nothing to go with. A recent study of arc flash incidents showed that if PPE was worn properly following calculations done with IEEE 1584, they walked away. If they did it following the tables in 70E, there was a 50% chance of injury. But on the other hand, at least you have an industry consensus safety standard to back you up so you can honestly say that you were putting forth the best effort possible.
Choice #3: Go with "maximum PPE" (40 cal? Higher?) This sounds good but as the incident energy increases, there are consistently many fewer panels that meet that rating, until you get to the "off the charts" category. This is where things like breakers fed directly by large transformers and breakers with settings that are too high live. So the 40 cal suit is only going to give you marginally better protection than following the tables in 70E and won't stop any "off the charts" cases anyways. So choice #3 may sound better than choice #2 but what a slippery slope it can be.


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PostPosted: Thu Feb 27, 2014 6:16 am 

Joined: Fri May 10, 2013 5:40 am
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Thank you for the input on this. The last study I performed, I had a facility electrician walk around with me and open devices and take covers off as needed. The company policy is that they wear Level 1 PPE as a standard uniform. The electrician opened all the covers and communicated the fuse size, breaker cat. no., etc. while I stood away and recorded the information. After the study was complete, I noted mentally that in most cases, while I was recording the information, I was within the limited approach boundary that was calculated. As a company, we are trying to decide the best way to approach this. Based on what I have read here, it may be better for us that we follow the 70E tables or have a qualified person record the information for us which we cannot readily get from the outside of the equipment...which is pretty much everything in older facilities with original equipment.


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PostPosted: Thu Feb 27, 2014 7:26 am 
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Joined: Mon Jan 18, 2010 11:35 am
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Location: Wisconsin
azahua wrote:
...while I stood away and recorded the information.

Why don't you get qualified and put on the appropriate PPE?


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PostPosted: Fri Feb 28, 2014 12:59 pm 
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azahua wrote:
Thank you for the input on this. The last study I performed, I had a facility electrician walk around with me and open devices and take covers off as needed. The company policy is that they wear Level 1 PPE as a standard uniform. The electrician opened all the covers and communicated the fuse size, breaker cat. no., etc. while I stood away and recorded the information. After the study was complete, I noted mentally that in most cases, while I was recording the information, I was within the limited approach boundary that was calculated. As a company, we are trying to decide the best way to approach this. Based on what I have read here, it may be better for us that we follow the 70E tables or have a qualified person record the information for us which we cannot readily get from the outside of the equipment...which is pretty much everything in older facilities with original equipment.


Limited approach boundary applies to shock, NOT arc flash. Do NOT confuse the two. Shock is shock. Arc flash is arc flash.

If the enclosures are grounded and the doors are closed and latched, your risk of shock is very close to nothing. Thus the shock protection boundaries disappear when the doors are closed because at that point there is nothing exposed.

Not so with arc flash. The hazard MAY still be there regardless of the state of the doors. It depends on exactly what you are doing, the dequipment design, and the state of the equipment. The risk of arc flash is as low as reasonably practical if one of the following is true:
1. The voltage is under 50 volts AC (unlikely to sustain an arc).
2. The equipment is designed, installed, and maintained to industry recommendations and the task considered would be considered normal operations.
3. The incident energy is very low (under 1.2 cal/cm^2, irrespective of relying on any protective devices).
4. The task does not interact with the equipment in such a way that it can cause an arc flash.

Standing there reading information off a label probably counts as #4 for arc flash hazards. Shock hazards though may exist if equipment is exposed. Older equipment that was built with wide open bus bars and otherwise essentially not built for safety of the qualified personnel is always a problem. Newer equipment usually is not exposed even with access doors open. And if this is the case then depending on where you stick your head/flashlight/mirror, it might fall into the "interacting" category.

Second is opening and closing access doors. There have been numerous arc flash incidents while removing or attaching bolted doors. I have not found any documentation of incidents while opening or closing hinged doors. However there are numerous theoretical reasons why opening and closing doors could cause an arc flash. For instance in a case in the last 7 years an electrician was removing the cover from a lighting panel and a 6 inch piece of steel fell into the bus bars and caused an arc flash. This is unlikely to happen with a hinged door on a properly installed and maintained panel board since all the openings will be closed up, but it could happen in an MCC or a poorly maintained panelboard.


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PostPosted: Mon Mar 03, 2014 7:09 am 

Joined: Wed May 06, 2009 12:12 pm
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Location: Tennessee
Personally I would always wear a shield, light leather gloves that you can write with, ear plugs and 8 cal coveralls for any 480 volt work. If it was fed with larger wires, say #2 or above I would wear a balaclava as well. I have personally seen an upper cover fall when a lower hinged door was opened for the very reasons of which you speak. I am here today because it missed the bus bars by inches. After the study, it turns out that in this case 8 cal PPE would not have been enough.

You don't know what the situation inside is until you look. In many industry settings systems are not properly maintained or may have deteriorated since the last maintenance cycle.


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PostPosted: Mon Mar 03, 2014 8:49 am 

Joined: Mon Mar 03, 2014 8:19 am
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I agree with PaulEngr regarding the hinged door issue, with a little reservation. I teach a lot of classes about the 70E and implementing an Electrical Safety Program. Last week while teaching one to a services company that specializes in back up power (including the related ATS equipment) two specific incidents were cited, in the class, relating directly to opening of hinged doors (in this instance an ATS) and unbolting a cover (400A power panelboard). Both were 480V. I've attached a photo of the result of the panelbaord cover being opened, but I do not know the detail of what exactly happened in the panelboard case. It is still under investigation (there was an injury requiring hospitalization, no death) and I include the newspaper photo to clearly show that bad things can happen when you do not know what is behind the cover. The ATS incident resulted in no injury or official report, but the internal company report indicated that the conductors connecting the door mounted devices to ATS internal components flashed to ground when the door was opened. This caused a short duration arc flash blindness in the technician. He was not further injured.
Again, without PPE, you are risking much. Using the tables as a default to get the information directly from the breakers is probably the best fall back process....better than nothing!


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