ARC FLASH LABELING - MAIN CIRCUIT BREAKER AND MAIN DISTRIBUTION SECTION

[PE (always learning)]

Hey everyone,

I have a question pertaining to a main distribution panel with several sections. We have a main section and then a distribution section. The main and the distribution section are attached and the main section says that it has a barrier separating it from the distribution section. My question is if my arc flash incident energy on the main section is above 40 cal/cm^2 does this also apply to the distribution section even though my breaker on the main mitigates the arc flash incident energy down to below 40 cal/cm^2 for the downstream breakers at the distribution section. Would I just apply one label that says not to work on this equipment live or could I put a label on the main section saying not to work on live and a label on the distribution section saying to apply the proper PPE?

Best Regards,
Engineer in training

 

[MyCleveland]

I would say the later is your solution, but I do not know the correct language for the label on the MAIN device section.

Question for you....how did you determine the MAIN section was over 40 ?
You asked the utility for TCC of there primary device and pulled your trip time from that ?

 

[JoeStillman]

Hey everyone,

I have a question pertaining to a main distribution panel with several sections. We have a main section and then a distribution section. The main and the distribution section are attached and the main section says that it has a barrier separating it from the distribution section. My question is if my arc flash incident energy on the main section is above 40 cal/cm^2 does this also apply to the distribution section even though my breaker on the main mitigates the arc flash incident energy down to below 40 cal/cm^2 for the downstream breakers at the distribution section. Would I just apply one label that says not to work on this equipment live or could I put a label on the main section saying not to work on live and a label on the distribution section saying to apply the proper PPE?

Best Regards,
Engineer in training

The first rule about working on live equipment is Never Work on Live Equipment.

I am no longer reluctant to tell people it can't be done. Use a red sticker.

Sent from my SM-G900V using Tapatalk

 

[wbdvt]

I assume the values you re citing are from a study? There may be some inside contained in the study. Even though there may be some sort of panel separating the main from the dist section, most people are wary about takiing credit for that blocking hot gases, plasma, etc from engulfing the main breaker without it being tested and deemed arc resistant.

 

[Strathead]

I question this as well. I have a main disconnecting means that I am told has 80 cal on the incoming secondaries. There is a barrier that prevents things from falling in to the incoming and shorting the phases together. I find it hard to accept that I can't turn off the main breaker and open up the enclosure in lieu of having the utility company come out and kill the service at the pole. The energy on the load side of the main is below 20 cal

 

[Sunny_92]

I question this as well. I have a main disconnecting means that I am told has 80 cal on the incoming secondaries. There is a barrier that prevents things from falling in to the incoming and shorting the phases together. I find it hard to accept that I can't turn off the main breaker and open up the enclosure in lieu of having the utility company come out and kill the service at the pole. The energy on the load side of the main is below 20 cal

I believe this is slightly different than what the OP is talking about. Here is how I would handle these situations:

For energized work when there is a barrier between the main section and distribution section - I believe the distribution section be labeled with the same incident energy rating as the main section. Reason being, if an arc flash were to occur in the distribution section, I would not trust the section barrier (likely plastic or non-arc rated metal) to prevent the arc from propagating into the main section and to the line side terminals.

For de-energized work when there is a barrier between the main section and distribution section - If the main breaker is turned off, there would be no exposed energized parts in the distribution section, so I believe de-energized work in the distribution section is acceptable. The tricky part with this would be protecting yourself appropriately when removing covers and verifying the absence of voltage.