120/208 volt Arc flash

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cornbread

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70E say if a 208/120 vac is fed with 125KVA or below a arc flash study is not needed.

Is it correct to assume a hazard risk catagory or 0.

Are there any calculations that would justify this assumption?
 
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cornbread said:
70E say if a 208/120 vac is fed with 125KVA or below a arc flash study is not needed.

Is it correct to assume a hazard risk catagory or 0.

Are there any calculations that would justify this assumption?
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That note is being removed from the 70E, but as of now it is still valid. It just means you do not need to do a study, it does not mean there is not a hazard. You should defer to the HRC's from the tables.
 
zog said:
That note is being removed from the 70E, but as of now it is still valid. It just means you do not need to do a study, it does not mean there is not a hazard. You should defer to the HRC's from the tables.
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Actually the TIA for removal of this note was voted down. The exception will be re-evaluated as part of the 2012 'update' cycle.

But Zog is correct, a study is not needed however the location can not be ignored. The best practice is to continue to use the task tables.
 
cornbread said:
70E say if a 208/120 vac is fed with 125KVA or below a arc flash study is not needed.

Is it correct to assume a hazard risk catagory or 0.

Are there any calculations that would justify this assumption?
Click to expand...


We don't even use risk catergory 0 when there's no arc flash calc required. Main hazard becomes shock. We call-out voltage rated gloves and voltage rated tools.
 
Sonny Boy said:
We don't even use risk catergory 0 when there's no arc flash calc required. Main hazard becomes shock. We call-out voltage rated gloves and voltage rated tools.
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Having no study required does not mean there is not a hazard. Gross misunderstanding of the 70E by your safety people.
 
We were trying to use our standard Arc Flash sticker and those labels have a section for cal/cm^2. I don't want to leave it blank, and I don't want to buy a seperate sticker for 208/120v panels? Would N/A suffice for the cal/cm^2?
 
cornbread said:
We were trying to use our standard Arc Flash sticker and those labels have a section for cal/cm^2. I don't want to leave it blank, and I don't want to buy a seperate sticker for 208/120v panels? Would N/A suffice for the cal/cm^2?
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Yes, IF you have the HRC from the tables on the label.
 
The more I read the more confused I get. So in the case of a 120v lighting panel fed from a 25 kva xfmr would the label say Hazard/Risk catagory 0 based on our standard text "when the covers removed", however if I look at 130.7(C)(9) I think I need to have a risk catagory of 1 for voltage testing, shoot why have the covers off a energized panel if your not taking a current or voltage measurment...ok...I/R scanning? In order to keep the electrical guys safe do we default to the higher level?
 
cornbread said:
The more I read the more confused I get. So in the case of a 120v lighting panel fed from a 25 kva xfmr would the label say Hazard/Risk catagory 0 based on our standard text "when the covers removed", however if I look at 130.7(C)(9) I think I need to have a risk catagory of 1 for voltage testing, shoot why have the covers off a energized panel if your not taking a current or voltage measurment...ok...I/R scanning? In order to keep the electrical guys safe do we default to the higher level?
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You have 3 options:

Do the analysis and label the panels with the calulated Ei
Have multiple labels for different tasks (Usually just confuses people)
Label with highest task based HRC from table, in this case HRC 1
 
I did the calcs (thank to the link you provided) and came up with approx. 1.2 cal/cm^2, hazard cat 0 correct? Since the calcs say it a cat 0 does that supercede the table?
 
cornbread said:
I did the calcs (thank to the link you provided) and came up with approx. 1.2 cal/cm^2, hazard cat 0 correct? Since the calcs say it a cat 0 does that supercede the table?
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Not sure how you calulated anything from that link, it was just an overview.

Yes if you did the calcs you only need the PPE rated for that level at your working distance. An arc flash study result supersceeds the tables. Your facility may require that calculation to be signed off and stamped by a PE. Where did you get your avaiable fault current and clearing times from? Did you calulate for min and max arcing currents?
 
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120v operator station labeling?

120v operator station labeling?

I have arc flash labels on 480v machines throughout the plant that show the PPE requirements and boundaries for both shock and arc flash hazards. A detailed analysis was performed to determine the incident energy using SKM program. I don't have many complaints regarding ratings and requirements for switchgears and industrial control panels from my personnel; they seem to understand that big panels may require extensive PPE. The problems are how to address the small stuff: such as remote operator interface panels on machinery, small 240/120v receptacle panels, etc.

I've done detailed analysis to 480v industrial control panel and determined it to be <1.2 cals. Panel contains 10kva transformer for 120v control power.

1. What labeling is required for remote operator stations that have 120v pushbuttons and selector switches?

2. Should the label have the full-blown shock data?

3. If I put a 1.2 cal arc flash rating on it, doesn't the machine operator have to wear cat 0 PPE which would have to be provided by the company? This could become very costly as everyone is a machine operator.

Where does 70E address this very low energy issue?
 
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