This week’s question is another one about arc flash labels.

How do you label equipment that is excluded from the calculations based on the 125 kVA transformer exception found in Both IEEE 1584 and NFPA 70E.

• No label is used
• A basic warning label is used
• Minimum 4 cal/cm^2 or HRC 1 label
• Minimum 8 cal/cm^2 or HRC 2 label
• Something else (please explain)

Exception Labels

We recommend the placement of a label on all equipment that would fall under NEC 110.16 ("likely to require examination, adjustment, servicing or maintenance while energized.") because the conscientious, qualified person should not look at an unlabeled location and assume that no hazard exists. Instead, he should be asking why it was left out.

For locations that fall under the exception, we recommend a label explaining the criteria for the exception (<125kVA, <240V, etc.) and labeling the hazard as <1.2 cal (or Category 0) with an 18" Boundary and 18" working distance.

We consider this an acceptably conservative way to address a location for which the hazard "need not be considered" [IEEE Std. 1584, p.6] while providing enough information to give confidence that the location was not overlooked during an assessment of the hazards.

Wally Tinsley
http://www.eaton.com

The equipment is only exempt from examination, not from the labelling requirements. There is a default minimim HRC for anyone performing live electrical work, being HRC 0 or HRC 1. If the minimum is HRC 0 then the label says IE of 1.2 cals and PPE of HRC 0, if the minimum is HRC 1, then the label says IE of 4.0 and PPE of HRC 1. Extrapolate for HRC 2 if that is your minimum.

The fact that the actual IE is something different doesn't make a difference for the label. I keep the fact that it was not-examinated on my spreadsheet. But the personnel performing the work were trained on HRC levels and IE requirements, and that's what they understand, so that is what the label says.

I also document the fact in my policy that the label on not-examined equipment will have IE values and HRC values that are not calculated and reference the NFPA exemption.

If you have a default minimum HRC of 1 or 2, do you require using a face shield for all electrical work, even operating LV breakers or motor starters where IE is < 1.2 cal/cm²? I can see standardizing on an arc rating for clothing, but not the related protective equipment.

130.3 Exception No. 1

I chose option #5 - something else. On the breaker panels meeting the exception, I forced the AF Hazard to 1.1 cal/cm^2 in the software for each individual breaker panel so that they fall into HRC 0 and the AF boundary then defaults to 4 ft. since this value is forced, not calculated. This enables us to print a label similar to the rest of the equipment showing the HRC, required PPE, AF boundary, shock protection boundaries and what that panel is fed by.

jghrist, our arc flash requirements are only for when performing live work, or operating switchgear. We have no arc flash requirements for operating LV breakers with covers on, or performing LOTO of MCC buckets.

Does that mean you don't label this equipment?

I should have added Category 0 to this list of choices

We follow the IEEE 1584 calculation method and label all panels and MCC accordingly. My point was that while performing routine operations with covers on, except for switchgear, we don't require any HRC PPE. Operators are permitted to turn off lights via circuit breakers in lighting panels, and perform LOTO on MCC buckets in their normal work attire. Dead front only of course.

Also assuming that the gear is in a well maintained condition (ie.. Door latches work and are in use, no holes in doors, etc..)...

We have electricians and an electrical engineer on staff. We use good quality gear manufactured by the top three industry leaders. If a cover or door was left in a state of dis-repair, there would be hell to pay. Infrared all electrical annually, switchgear is high current tested and serviced every 3 years. We feel comfortable in our decisions.

I see nothing wrong with this approach. It should be defined in an Electrical Safety Procedures document and should be based on some hazard/risk evaluation. How it is documented and how the hazard/risk evaluation is done is up to the company. These kind of questions become more difficult for an outside engineer.