120/208 volt Arc flash
- Thread starter cornbread
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zog
Senior Member
- Location
- Charlotte, NC
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.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
zog
Senior Member
- Location
- Charlotte, NC
Thanks Jim, didn't get that update. Where did you hear that?
Found this doing a search, does this have any validity?
http://www.bnl.gov/esh/esc/PDFs/Use of Voltage-Rated Gloves - 120V Single Ph. Circuits.pdf
http://www.bnl.gov/esh/esc/PDFs/Use of Voltage-Rated Gloves - 120V Single Ph. Circuits.pdf
Sonny Boy
Member
- Location
- Washington
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.
zog
Senior Member
- Location
- Charlotte, NC
Having no study required does not mean there is not a hazard. Gross misunderstanding of the 70E by your safety people.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
As of the 2009 edition, the 10k SCA limit for reducing arc flash HRC values is no longer part of NFPA 70E. It would be interesting to see if this policy has been modified.
weressl
Esteemed Member
zog
Senior Member
- Location
- Charlotte, NC
Thats what the tables are for.
zog
Senior Member
- Location
- Charlotte, NC
Yes, IF you have the HRC from the tables on the label.
zog
Senior Member
- Location
- Charlotte, NC
Here is a good article on the subject, note the comparisions of the table values to the calculated values for a 240V 50kVA source.
http://www.etap.com/support/articles/electrical-safety-measures-2009/etap-arc-flash-esm.pdf
http://www.etap.com/support/articles/electrical-safety-measures-2009/etap-arc-flash-esm.pdf
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?
zog
Senior Member
- Location
- Charlotte, NC
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
zog
Senior Member
- Location
- Charlotte, NC
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?
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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