Arc Flash label requirements in 2011 NEC section 110.16

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mull982

Senior Member
I dont have the 2011 NEC in front of me but can anyone tell me or explain to me the requirements of section 110.16 in the new 2011 code? In the 2008 version of the code the section required panels, enclosures, etc.. to be field marked or labeled with a generic label warning of an Arc Flash hazard but did not require this label to have specifics such as the amnount of Incident Energy, Specific Flash Boundary, or Category that you find on lablels produced from an AF study.

I thought I overheard someone saying that the new 2011 code required specific Arc Flash labels on equipment with specific information as a result of an AF study. Can anyone verify this or explain what is required in the 2011 code?

Thanks
 

jumper

Senior Member
110.16 is the same, it is 110.24 that is new.

Here it is:

110.24 Available Fault Current.
(A) Field Marking. Service equipment in other than
dwelling units shall be legibly marked in the field with the
maximum available fault current. The field marking(s) shall
include the date the fault current calculation was performed
and be of sufficient durability to withstand the environment
involved.
(B) Modifications. When modifications to the electrical
installation occur that affect the maximum available fault
current at the service, the maximum available fault current
shall be verified or recalculated as necessary to ensure the
service equipment ratings are sufficient for the maximum
available fault current at the line terminals of the equipment.
The required field marking(s) in 110.24(A) shall be
adjusted to reflect the new level of maximum available
fault current.
Exception: The field marking requirements in 110.24(A)
and 110.24(B) shall not be required in industrial installations
where conditions of maintenance and supervision ensure
that only qualified persons service the equipment.
 

raider1

Senior Member
Staff member
Location
Logan, Utah
Derek pointed out the new requirement in the 2011 NEC that requires the available fault current to be marked on the service equipment.

Now do not confuse this requirement with arc flash incident energy marking requirements from NFPA 70E. The requirements are very different.

The available fault current that is required to be marked on the service equipment is used to comply with 110.9 and 110.10 for making sure that the AIC rating of overcurrent devices and the SCCR rating of other equipment is adequate to handle the available fault current.

The arc flash labeling requirements from 70E are not mandated by the NEC.

Chris
 

mull982

Senior Member
Thanks guys

Raider

Yes I am aware of the differences between the two different types of labels. I was just curious weather or not the new NEC required anything other than the generic Arc Flash warning label on equipment in regards to Arc Flash. Apparently only the generic Arc Flash label is still required.

It also looks like a label for avaliable SS current is also required with the new code.

I know that 70E requires Arc Flash labels, but cant recall what section this is in. Can anyone help with this?

Also does the NEC require in any way that that requirements of 70E are followed thus ensuring that specific Arc Flash labels are required? Or does the NEC simply only reference 70E but does not specifically require it to be followed.
 

skeshesh

Senior Member
Location
Los Angeles, Ca
110.24 Available Fault Current.
(A) Field Marking. Service equipment in other than
dwelling units shall be legibly marked in the field with the
maximum available fault current. The field marking(s) shall
include the date the fault current calculation was performed
and be of sufficient durability to withstand the environment
involved.

Does "maximum" imply that a less accurate method like assuming an infinite bus and just using xfmr impedance is acceptable? For smaller projects obtaining available fault at the transformer could be a pain and also impact the schedule. I'm guessing infinite bus is fine since it is a conservative scenario and NEC's intent is safety.
 

raider1

Senior Member
Staff member
Location
Logan, Utah
Does "maximum" imply that a less accurate method like assuming an infinite bus and just using xfmr impedance is acceptable? For smaller projects obtaining available fault at the transformer could be a pain and also impact the schedule. I'm guessing infinite bus is fine since it is a conservative scenario and NEC's intent is safety.

Correct, the infinite bus method is acceptable for the requirements in 110.24.

Chris
 
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