Confused on 70E - <240V / <240V Labels

[jacknife76]

I was reading an old post in which the discussion was about an arc flash analysis for a circuit below 240V

According to 130.3 Exception No. 1, an AF hazard analysis is not required if the circuit is <240V and fed by a single xfrmr <125kVA
But that doesn't mean there isn't still a flash hazard, does it? I read that as: there is no detailed analysis required, but you then must use Table 130.7(C)(9) and use the category/PPE per task.

(I realize I just asked this question a few weeks ago, but after reading an old post, people were saying that since there is no analysis required, there is no hazard and no PPE is required. I felt that to be incorrect and I hope no one reads that post and uses the information incorrectly.)

My second question is regarding 130.3(C):
If you have a 120V lighting panel that meets the requirements of 130.3 Ex. 1 (i.e., <240V and fed from a single 125kVA), you are not required to complete an analysis. If you can use Table 130.7(C)(9), as applicable per task, how can you label the panel with a specific label (IE or PPE) if it changes according to task?

Thanks

 

[zog]

I was reading an old post in which the discussion was about an arc flash analysis for a circuit below 240V

According to 130.3 Exception No. 1, an AF hazard analysis is not required if the circuit is <240V and fed by a single xfrmr <125kVA
But that doesn't mean there isn't still a flash hazard, does it? I read that as: there is no detailed analysis required, but you then must use Table 130.7(C)(9) and use the category/PPE per task.

(I realize I just asked this question a few weeks ago, but after reading an old post, people were saying that since there is no analysis required, there is no hazard and no PPE is required. I felt that to be incorrect and I hope no one reads that post and uses the information incorrectly.)

You are correct, who ever said that is wrong. Still need PPE per the tables, just are not required to do a detailed study.

My second question is regarding 130.3(C):
If you have a 120V lighting panel that meets the requirements of 130.3 Ex. 1 (i.e., <240V and fed from a single 125kVA), you are not required to complete an analysis. If you can use Table 130.7(C)(9), as applicable per task, how can you label the panel with a specific label (IE or PPE) if it changes according to task?

Thanks

Good question that confuses a lot of people. Some plants post a "task/PPE" matrix on the equipment, but most take the safe approach and post the highest HRC for the equipment.

 

[jacknife76]

That's what I figured (labels).

Thanks.

 

[brainfiller]

The whole issue stems from attempting to copy some language from IEEE 1584 The thought behind this exemption from arc flash calculations was a fault downstream from a 125 kVA transformer at 208 V:

a) Would be a lower short circuit current since it would be transformer limited
b) Likely not sustain since it is at a very low voltage (combined with low current)

However, there is still an arc flash, just not a severe one (in theory)

I am heading up a task group of IEEE 1584 to evaluate this further. The IEEE exception will likely be changing in the future. I was involved with some arc flash testing in January and you CAN sustain an arc flash at lower currents given the right (and realistic) circumstances.

My thought is this exemption from the IEEE perspective will likely become current based rather than kVA so it can be applied on circuits that have low short circuit current rather than just based on transformer kVA alone. What I saw in the lab was arcs sustained down around 5 to 6 kA.

Hope it helps.

Jim Phillips, P.E.

 

[bob04]

<240v labels?

<240v labels?

What shock/arc flash labeling is required on remote operator pushbutton stations (120v)? Assume it is supplied from a 480v industrial control panel rated at < 1.2cals.

Has anyone had OSHA weigh in on this issue yet, inspection or training course?