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 Post subject: What do arc flash labels mean ?
PostPosted: Sat Aug 31, 2013 6:31 pm 

Joined: Sat Aug 31, 2013 6:02 pm
Posts: 3
This is something hard for me to get across to safety and really need help with a answer , which I think I am right. We have a 300amp breaker in a panel for a motor with level 4 arc flash label on the door. Can or should this breaker be operated by some one in less than level 4 ppe with door closed ? Also is this anywhere to be found in 70e. The only thing I was able to find is in section 205 in 70e.
Some people say no arc flash because door is closed.


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PostPosted: Tue Sep 03, 2013 6:32 am 
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Joined: Mon Jan 18, 2010 11:35 am
Posts: 525
Location: Wisconsin
Doors have no affect on the choice of PPE.
The cal/cm² exist regardless of the status of the door.

About the only thing doors might do is change the Risk of an arc flash occurring.

If the interaction with the breaker is likely to cause an arcing event (e.g. history of infrequent operation) then maximum PPE is definitely a good idea.


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PostPosted: Tue Sep 03, 2013 8:43 am 

Joined: Tue Sep 03, 2013 8:39 am
Posts: 1
Location: Knoxville, TN
Informational Note #2 under Article 130.7 of NFPA-70E-2012.
States "
that normal operation of enclosed electrical equipment,
operating at 600 volts or less, that has been properly
installed and maintained by qualified persons is not likely
to expose the employee to an electrical hazard."
Therefore, Level 4 PPE is only required when accessing the breaker, for maintenance , testing etc. (Door open)


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PostPosted: Tue Sep 03, 2013 9:26 am 

Joined: Thu Jul 21, 2011 4:21 pm
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Based on the situation described (with doors closed), level 4 PPE should not be required. PPE is required if the worker is within the arc flash boundary which is a specified distance from exposed energized components. There is no exposure to energized components if the door is closed. That isn't to say that some level of PPE should not be used. The HR tables of 70E address this situation.

Let's change the scenario a little bit. Instead of a level 4, 300A breaker, let's use a 2000A main service disconnect with a rating of Danger - Do Not Touch. In this scenario, you would never be able to open or close this breaker.

I would not operate a device within a level 4 bus without some level of PPE. For many of our clients, this is handled in their safety program. For instance, where an arc flash study has been performed in accordance with 1584, a worker must be in level 0 PPE when operating a breaker in a board rated level 2 or less. Otherwise, they must be in level 2.


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PostPosted: Tue Sep 03, 2013 3:31 pm 

Joined: Sun Feb 14, 2010 9:28 pm
Posts: 21
Location: Queensland
Having a door closed does not necessarily protect you. Internal Arc Contained switchgear (IAC) is type tested to a standard to confirm its arc containment capabilities. But that does not mean that internal arcing faults will be contained in all cases. The testing is based on certain criteria. If the criteria are not met, then containment cannot be assured. Typically, this might include protection clearance time of the fault in excess of the type test time. I have photos of various HV & LV switchgear both IAC type tested and not type tested where doors have blown open and arc gases have been projected toward the operator. Generally, these relate to long fault clearance times (> 200ms). In your arc flash risk assessments, it is important to evaluate the type test results for your switchgear and consider the fault clearance times. Recall that maintenance of the protection scheme (circuit breaker & relay, fuse sizing, flash detection system etc) is required to assure its functionality. An unmaintained system may not protect you.
In those cases where there is historical evidence of fault containment, your risk assessments may give some credit to the door for similar faults. This is reflected in the tables of 70E. In cases of >40cal (isolate elsewhere), upstream isolation can permit operation of the CB (de-energised) and its use as an isolation point. Alternately, the CB may still be operated by remote means (where provided).
Your labels may stipulate PPE requirements for operation, which may differ to those for maintenance. Door open vs door closed can be different.


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PostPosted: Tue Sep 03, 2013 6:57 pm 

Joined: Sat Aug 31, 2013 6:02 pm
Posts: 3
Let me add that this panel / cb is feed upstream from a switchgear breaker [dangerous] that has not had any pm or attention in a good ten years.


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PostPosted: Wed Sep 04, 2013 1:16 am 
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I agree with GBISON in as much that there is no guarantee that the enclosure will contain the arc flash. In fact I have a similar situation whereby I have an isolator with a 19cal/cm2 rating, which warrants PPE at level 3. For switching purposes I have recommended a isolation regime whereby the upstream f/sw ( arc flash rated at 2.6cal/cm2 PPE 1) is used as initial isolation and locked off. Subsequently the local isolator is then operated and locked off. Re-energisation is just a straight reversal.
Both f/sw and isolator have an arc flash label affixed to them.
The root of the problem lies in the cable size and length. The correct solution electrically should be to increase cable size and use an alternative supply from a nearer source. This should increase the PFC and reduce the clearing time.


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PostPosted: Mon Sep 09, 2013 7:43 pm 

Joined: Wed Oct 19, 2011 12:52 pm
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Location: Vero Beach, Florida
You did not say at what voltage level this breaker was applied.

Table 130.7(C)(15)(a) indicates under "Metal clad switchgear, 1kV through 38 kV" that "CB operation with doors closed" is a Level 2 Hazard/Risk. With doors open it jumps to 4. Maybe the logic behind the Level 4 label is that the conservative approach is to assume the doors are open.

Another factor to considered is the short circuit interrupting rating of the breaker compared to the calculated short circuit current. If the breaker is over-dutied, whether the doors are closed or open may not make much difference because the breaker may explode if a short circuit occurs during the breaker operation.

My suggestion would be to calculate the maximum short circuit current at the breaker and if it is less than the breaker rating and assuming that the breaker has been maintained properly in accordance with the manufacturer's instruction, wear PPE 2 and ensure that the doors are indeed closed. Otherwise wear PPE 4.

For 600V class MCCs, switchgear or contractor with the doors closed, CB, fused contractor or starter operations are classified in the NFPA Table as PPE 0.

Hope this helps.


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PostPosted: Mon Sep 16, 2013 7:14 am 
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Joined: Mon Jun 02, 2008 11:58 am
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Location: Charlotte, NC
maintenance wrote:
Let me add that this panel / cb is feed upstream from a switchgear breaker [dangerous] that has not had any pm or attention in a good ten years.

Where did the HRC 4 on the label come from? Tables or an arc flash study?

Either way, since your equipment is not properly maintained, you are still required to use PPE, or remote switching.


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PostPosted: Mon Sep 16, 2013 7:17 am 
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Joined: Mon Jun 02, 2008 11:58 am
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Location: Charlotte, NC
tmmccauley wrote:
You did not say at what voltage level this breaker was applied.

Table 130.7(C)(15)(a) indicates under "Metal clad switchgear, 1kV through 38 kV" that "CB operation with doors closed" is a Level 2 Hazard/Risk. With doors open it jumps to 4. Maybe the logic behind the Level 4 label is that the conservative approach is to assume the doors are open.

Another factor to considered is the short circuit interrupting rating of the breaker compared to the calculated short circuit current. If the breaker is over-dutied, whether the doors are closed or open may not make much difference because the breaker may explode if a short circuit occurs during the breaker operation.

My suggestion would be to calculate the maximum short circuit current at the breaker and if it is less than the breaker rating and assuming that the breaker has been maintained properly in accordance with the manufacturer's instruction, wear PPE 2 and ensure that the doors are indeed closed. Otherwise wear PPE 4.


If you are using the tables you need to know the availble fault current anyways. If it exceeds the limits of the notes for that equipment you can't use the HRC's from the tables. If it exceeds the AIC rating of the breaker then you have much bigger problems.


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PostPosted: Wed Sep 25, 2013 1:25 am 

Joined: Sat Aug 31, 2013 6:02 pm
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They used the information supplied from the survey - study completed less then a year ago. The voltage is 480.
Apologize for not getting back quicker. Thanks to everyone for replying.


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PostPosted: Wed Sep 25, 2013 8:57 am 
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Location: Rutland, VT
Since the statement is made about this breaker being fed from an upstream switchgear breaker that has not had any maintenance in a good 10 years, I would question that the breaker in question here has not been maintained either. Aside from operating the breaker, has it been inspected for cracks in the phenolic case? Dust cleaned off it? Lugs checked for signs of overheating? etc.

I would go with the HRC 4 PPE. If this is operated frequently (have you exceeded manufacturers recommended number of operations?), you should look at the upstream breaker feeding this for improvements. For example: what is the trip unit on this breaker? Is it an old solid state or worst none solid state such as a GE EC device? You may be able to lower the hazard with a modern trip unit.

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Barry Donovan, P.E.
www.workplacesafetysolutions.com


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