My question is on the interpretation of 240 volt up to 600 volt molded circuit breaker operations with covers on. There are several locations in a facility where untrained non-electrical personnel switch 277 lighting circuit breakers on and off as needed. When one reads the chart from NFPA 70 E it would seem that this would be an unacceptable practice because of the ZERO HRC/Risk category. What are your thoughts?
NFPA 70 E Table 130.7(c)(9) (a) question
- Thread starter jerryjtb
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zog
Senior Member
- Location
- Charlotte, NC
You are right, but you have 3 options.
Option 1 - Train them on the hazards associated with that specific task including the PPE required.
Option 2 - Have a qualified person operate the breakers for them
Option 3 - Conduct an arc flash hazard analysis at your facillity. You may find that there is no (or miminal) arc flash hazard that requires any PPE if the arc will not be self sustaining, the tables make several assumptions about your system and many times an actual analysis will show less of a hazard than the tables indicate.
Besides the 70E issues there may be a serious OSHA vioalation here. If they are resetting the breaker after a fault they need to ensure the circuit is safe to re-energize by testing the circuit per OSHA 1910.334(b)(2).
Option 1 - Train them on the hazards associated with that specific task including the PPE required.
Option 2 - Have a qualified person operate the breakers for them
Option 3 - Conduct an arc flash hazard analysis at your facillity. You may find that there is no (or miminal) arc flash hazard that requires any PPE if the arc will not be self sustaining, the tables make several assumptions about your system and many times an actual analysis will show less of a hazard than the tables indicate.
Besides the 70E issues there may be a serious OSHA vioalation here. If they are resetting the breaker after a fault they need to ensure the circuit is safe to re-energize by testing the circuit per OSHA 1910.334(b)(2).
- Location
- Wisconsin
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- PE (Retired) - Power Systems
Why would this be "unacceptable"? Don't you train your employess how to operate a circuit breaker and the associated hazards of performing that task?
I believe the task tables are hard to implement for most every day situations when equipment is operated as it is intended (i.e. per UL standards and manufacturers instructions). For example, article 130 is only applicable if the employee is "Working On or Near Live Parts". 130.1(A)(1) requires a permit when performing live work (unless exempted in 130.1(A)(3)). Therefore isn't a live work permit as well as PPE required to simply turn things on and off?
I believe the task tables are hard to implement for most every day situations when equipment is operated as it is intended (i.e. per UL standards and manufacturers instructions). For example, article 130 is only applicable if the employee is "Working On or Near Live Parts". 130.1(A)(1) requires a permit when performing live work (unless exempted in 130.1(A)(3)). Therefore isn't a live work permit as well as PPE required to simply turn things on and off?
zog
Senior Member
- Location
- Charlotte, NC
If the covers are on then there are no exposed live parts and an EEWp would not be required. However, PPE may still be required for arc flash protection.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
zog said:
If EEWP is not required because you are not working on or near live parts why should the task table 130.7(C)(9) be applicable? 130.7(A) says PPE is only required if a hazard exists.
For example, if you are operating a UL Listed overcurrent protective device in a UL/NEMA 12 enclosure within its SCCR/AIC rating and with the its cover closed what arc flash hazard exists? UL standards require that this equipment door stay closed and that cotton packed around the enclosure does not ignite while operating during a short circuit. Of course if the equipment is being used outside of its ratings 130.6(H) is applicable.
I am not argueing with the intent behind NFPA 70E, I simply think the task table 130.7(C)(9)(a) (which requires a flash boundary per 130.3(A)). is not as easily implemented as many people believe.
zog
Senior Member
- Location
- Charlotte, NC
Dont confuse shock hazards with arc flash hazards. If there are no exposed live parts there is not a shock hazard but still is an arc flash hazard. The arc flash boundaries and PPE requirements are in effect when you are "Interacting" with the equipment. Even with the covers on if you operate a breaker or switch that may cause an arc flash to occur, the arc flash (blast) may very well blow the doors or panel covers off.
I would really like to see this cleared up. At our facility we require arc flash PPE to operate a fused disconnect with the door closed, but do not require PPE to operate 277V switch rated breakers with all covers on.
Generally we also require arc flash rated PPE if there are "exposed energized parts."
Generally we also require arc flash rated PPE if there are "exposed energized parts."
zog
Senior Member
- Location
- Charlotte, NC
Wdean,
Are you using the tables or have you conducted an analysis?
Are you using the tables or have you conducted an analysis?
zog-
We are conducting an analysis. We are providing labels at all 480V and above panels, disconnects, switchgear, etc.
The question has come up about when to wear PPE? What tasks require it. We are trying to follow the same tasks as 70E, but generally provide caveat for "exposed energized parts."
We are conducting an analysis. We are providing labels at all 480V and above panels, disconnects, switchgear, etc.
The question has come up about when to wear PPE? What tasks require it. We are trying to follow the same tasks as 70E, but generally provide caveat for "exposed energized parts."
zog
Senior Member
- Location
- Charlotte, NC
So you are doing an analysis at 480V and above but not at less than 480V?
Then you are using the tables for equipment less than 480V?
If both answers are yes then why?
Typically if you do an analysis to a point and then use the tables the cutoff would be panels less than 240V that are supplied by a transformer less than 125kVA per the IEEE 1584.
The majority of the work (See cost) of an analysis is the S/C and coord study, your 277V equipment is (Should be) already included in the S/C study and the PDC study would involve just a little more data collection. After that it is just a matter of pushing a button to do the Arc Flash study on the 277V stuff and print the labels.
When to wear PPE?
PPE for shock protection (Rubber Gloves, etc.) is required when working inside the RAB of exposed energized parts.
PPE for arc flash protection (FR Clothing, etc.) is to be worn when "Working" on or near energized equipment, regardless of the status of the covers. Any "interaction" with energized equipment requires the use of proper PPE for arc flash protection. If you are using the tables method to operate a 277V breaker, the PPE required is HRC 0 (Long sleeve natual fiber shirt and pants and non conductive safety glasses)if you have <25kA S/C current available with a clearing time of 2 cycles or less. If you dont meet the S/C and clearing times in note 1 you cannot use the tables to select the proper PPE.
Then you are using the tables for equipment less than 480V?
If both answers are yes then why?
Typically if you do an analysis to a point and then use the tables the cutoff would be panels less than 240V that are supplied by a transformer less than 125kVA per the IEEE 1584.
The majority of the work (See cost) of an analysis is the S/C and coord study, your 277V equipment is (Should be) already included in the S/C study and the PDC study would involve just a little more data collection. After that it is just a matter of pushing a button to do the Arc Flash study on the 277V stuff and print the labels.
When to wear PPE?
PPE for shock protection (Rubber Gloves, etc.) is required when working inside the RAB of exposed energized parts.
PPE for arc flash protection (FR Clothing, etc.) is to be worn when "Working" on or near energized equipment, regardless of the status of the covers. Any "interaction" with energized equipment requires the use of proper PPE for arc flash protection. If you are using the tables method to operate a 277V breaker, the PPE required is HRC 0 (Long sleeve natual fiber shirt and pants and non conductive safety glasses)if you have <25kA S/C current available with a clearing time of 2 cycles or less. If you dont meet the S/C and clearing times in note 1 you cannot use the tables to select the proper PPE.
WDeanN said:
Having covers on and/or doors closed will decrease your level of arc flash hazard but of course, just standing a foot farther away from equipment decreases the hazard as you can see by the distance figure that's input into your arc flash calculation.
But having covers on/doors closed doesn't eliminate the arc flash risk. . Like mentioned before, a high calorie arc flash can propel a door/cover at you like a projectile. . How well is the door/cover actually bolted on ? . Does it provide any barrier protection against the flash/explosion or does it increase projectile risk ? . What is the weakest link on the cover or the attachment of the cover ? . Are the cover holes large ? . How much do the bolt heads overlap the cover steel ?
All that stuff makes a difference when a blast occurs.
David
zog
Senior Member
- Location
- Charlotte, NC
Well put David.
Now if the switchgear is arc rated switchgear that is a different story. The 2008 70E will include operation of arc rated switchgear tested IAW IEEE c37.20.7 into the tables. Arc rated switchgear is fairly common in Canada (So I hear, Eh) but just starting to show up in the US.
Now if the switchgear is arc rated switchgear that is a different story. The 2008 70E will include operation of arc rated switchgear tested IAW IEEE c37.20.7 into the tables. Arc rated switchgear is fairly common in Canada (So I hear, Eh) but just starting to show up in the US.
zog
Senior Member
- Location
- Charlotte, NC
Here is ABB's safegear (Takes a few minutes to run)
http://library.abb.com/GLOBAL/SCOT/scot235.nsf/VerityDisplay/5115147E06AB6F7385256BA600616D80/$File/arcres.mov
http://library.abb.com/GLOBAL/SCOT/scot235.nsf/VerityDisplay/5115147E06AB6F7385256BA600616D80/$File/arcres.mov
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
How about installing wall switches for the lighting? That may be more cost effective/safer.
dnem said:
David (and Zog) -
How do you support this opinion?
I don't see anything in 1584 or 70E that takes this information into account for an arc flash calculation.
There is nothing in 70E or 1584 about calculating arc flash energy levels with the doors/covers in place.
Jim's posts #3 and #5 appear to be exactly in accordance with 70E.
What you are advocating might be a good idea - might even be a great idea - just not supported by any peer reviewed literature or testing.
carl
zog
Senior Member
- Location
- Charlotte, NC
Are you asking about arc rated switchgear? You wont find that in the 70E or 1584, but there are several proposals that were accepted regarding arc rated switchgear for the 2009 70E, due out October 2008.
I think Arc Rated stuff is just too new to have been considered in any current standards.
I think Arc Rated stuff is just too new to have been considered in any current standards.
coulter said:
I was answering WdeanN who had posted in post #9 that they had already done an analysis but were debating their internal policy of treating "exposed energized parts" differently from nonexposed. . The subject was no longer the arc flash calculation but rather determining the logic or illogic of their policy. . My conclusion was:
“All that stuff makes a difference when a blast occurs.”
My point being that if you decide to allow untrained people to reset breakers in your plant without any PPE, you are making an arbitrary decision without considering either NFPA70E or thinking thru the issue. . When talking about projectile risk or weakest link or bolt heads, I was talking about thinking thru a policy, not analyzing an arc flash calculation.
WDeanN said:
WDeanN said:
You’ll see he said they had conducted the analysis and were now looking at how to apply it.
coulter said:
And that was my point. . What happens after the arc fault calculation is application of logic and the making of policy.
David
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