ARC FLASH LABELING OF INDUSTRIAL CONTROL PANELS AND HVAC EQUIPMENT

engineerintraining12

Senior Member
Location
Saint Louis
That statement can be true for any piece of equipment with an arcing fault. An arcing fault can be very destructive with molten metal being airborne. So unless the piece of equipment is designed and tested as arc resistant, based on the statement above, an arc flash label should not be installed on any piece of equipment as one does not know what is going to happen.
Do you provide arc flash labels for equipment that is over-dutied? From what I gather, the consensus is to flag the equipment and provide suggestions for remedial action, possibly including upgrade or replacement of the affected equipment in order to comply with the NEC and NFPA 70E.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
Do you provide arc flash labels for equipment that is over-dutied? From what I gather, the consensus is to flag the equipment and provide suggestions for remedial action, possibly including upgrade or replacement of the affected equipment in order to comply with the NEC and NFPA 70E.
I provided labels.
I flagged overdutied protective devices, per NEC 110.09.
I flagged overdutied equipment per NEC 110.10.
It was not my place to dictate work practices to a customer.

A protective device AIC is based on the short circuit current available at its line side terminals. Being overdutied may have no or little impact on its ability to clear a downstream fault and therefore impact a downstream incident energy.

A piece of equipment that has an insufficient SCCR means it is likely going to be damaged by a large enough fault current, although arcing fault event is also likely to cause damage, especially with a high incident energy level.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I think you should label the control panels with the SCCR (including any that you assume to be 5 kA), what you calculated the available SCC to be, and the incident energy at the enclosure (along with the required PPE).

These are three separate items that are only somewhat related.

You might also want to label any control panels where the available SCC exceeds the SCCR as potentially dangerous due to this situation that you are calling "over dutied". I would not get real excited about it though. In the real world the calculated available SCC often exceeds the real SCC by a lot, and in most cases these things have been around a long time without it being an issue.

I would focus remediation efforts on cases where there is a really serious safety issue. Otherwise they will get overwhelmed with the scale of the problem and probably do nothing.

You may find when you start looking that a fair number of the control panels are not as unsafe as you think. Some of these control panels may have been around since long before anyone even thought of requiring a SCCR.

A typical way of handling SCCR of control panels back in the 1980s was to put in current limiting fuses and call it good. that would never fly today but it was a common practice back then and it is not like a crap load of control panels exploded.
 

wbdvt

Senior Member
Location
Rutland, VT, USA
Occupation
Electrical Engineer, PE
Do you provide arc flash labels for equipment that is over-dutied? From what I gather, the consensus is to flag the equipment and provide suggestions for remedial action, possibly including upgrade or replacement of the affected equipment in order to comply with the NEC and NFPA 70E.
For equipment where the bolted fault current exceeds it's SCCR, I do label that equipment with the incident energy level for that equipment as that is not going to change based on the SCCR of the equipment. You will have the same arc flash hazard at that location whether the SCCR is exceeded or not.

For OCPD where the AIC rating is exceeded, I ignore those devices in my analyzes and use the next upstream device. This results in, usually, a much higher IE level on the downstream equipment being protected by this device. This usually gets people to replace the OCPD's that are overdutied.

My report flags all over-dutied equipment and I provide recommendations to resolve the issues.

Note that overdutied equipment is also a violation of OSHA 1910.303 and this will sometimes get more attention than being in violation of the NEC
 
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