NFPA 70E

Electriman

Senior Member
Location
TX
Greetings,

Per NEC and NFPA 70E latest edition, which panels do they need to have:
(1) No arc flash label
(2) Basic AF label to warn about the AF hazard
(3) A detail AF label with calculated incident energy
 

paulengr

Senior Member
NEC has a list but it is just EXAMPLES, not an exact list. Essentially anything that is “frequently” accessed. Also not in either one but a suggested test for “frequently” is once per year or more often. So disconnects, panelboards, switchboards and switchgear count but say motor peckerheads don’t. But if say you have a conveyor and the easiest way to reverse it is through the peckerhead, the peckerhead gets a label even though it’s not on the examples list in NEC. As I said it only lists examples not a hard and fast list.

NEC only requires a label. Or equivalent. It says nothing of what’s on it. So the “generic” “warning — arc flash hazard” is all you are required to label. The label must be field applied although some distribution panels come with a factory generic label,

70E is 100% voluntary. You don’t have to follow it or follow it to the letter. For example in steel mills, power plants, and refineries FR is required and OSHA starts with 4 cal for basically everywhere for utilities. So many plants just start labels above that point and have procedures to cover everything else.

Arc flash in utilization equipment falls under the general duty clause of OSHA. You can do ANYTHING you want as long as you have some standard. With generation, transmission, and distribution equipment OSHA has specific arc flash rules under 1910.269 that are different from and conflict with both 70E and NESC. NEC references 70E but does not require it (it’s in an informational note).

70E requires a lot of specific information on the label but they support two systems. You can either use the table method in 70E or what they call the engineering method. Under the engineering method the assumption is to use IEEE 1584 but realistically you can use anything you want provided it is justifiable. Since 70E is voluntary it is a recommendation, not a requirement. You can do anything you want on the labels. The only danger here is can you explain what you are doing to an OSHA inspector?

For instance 1584 is very generic and does not take equipment specific conditions into account. They literally just hang three bus bars inside a cabinet and create an arc flash. So it only really simulates junction boxes. As soon as you add equipment into the box, it shields some of the heat and absorbs some of it. This causes the incident energy to drop off a lot. So say with MCC do we calculate the arc flash from an empty bucket (prepared space) or any empty section? Calculating with a section filled with buckets is impossible. Actual MCC tests have arc flash that is vastly less than what IEEE 1584 predicts.

IEEE 1584 is known to way over predict all 240 V and below equipment as an example. NESC says it’s 4 cal/cm2 regardless of other factors. This is based on the highest measured incident energy under the most extreme circumstances (3.2 cal/cm2). The highest incident energy ever measured on a 125 VDC battery system simulation is 1.2 cal/cm2. So not labeling this stuff if you are in an “FR mandatory” plant is well justified, or using the “generic” label.

So do not make the mistake of thinking NEC and 70E are identical. NEC depending on where you are working may be legally required. 70E is a recommendation.
 

Electriman

Senior Member
Location
TX
NEC has a list but it is just EXAMPLES, not an exact list. Essentially anything that is “frequently” accessed. Also not in either one but a suggested test for “frequently” is once per year or more often. So disconnects, panelboards, switchboards and switchgear count but say motor peckerheads don’t. But if say you have a conveyor and the easiest way to reverse it is through the peckerhead, the peckerhead gets a label even though it’s not on the examples list in NEC. As I said it only lists examples not a hard and fast list.

NEC only requires a label. Or equivalent. It says nothing of what’s on it. So the “generic” “warning — arc flash hazard” is all you are required to label. The label must be field applied although some distribution panels come with a factory generic label,

70E is 100% voluntary. You don’t have to follow it or follow it to the letter. For example in steel mills, power plants, and refineries FR is required and OSHA starts with 4 cal for basically everywhere for utilities. So many plants just start labels above that point and have procedures to cover everything else.

Arc flash in utilization equipment falls under the general duty clause of OSHA. You can do ANYTHING you want as long as you have some standard. With generation, transmission, and distribution equipment OSHA has specific arc flash rules under 1910.269 that are different from and conflict with both 70E and NESC. NEC references 70E but does not require it (it’s in an informational note).

70E requires a lot of specific information on the label but they support two systems. You can either use the table method in 70E or what they call the engineering method. Under the engineering method the assumption is to use IEEE 1584 but realistically you can use anything you want provided it is justifiable. Since 70E is voluntary it is a recommendation, not a requirement. You can do anything you want on the labels. The only danger here is can you explain what you are doing to an OSHA inspector?

For instance 1584 is very generic and does not take equipment specific conditions into account. They literally just hang three bus bars inside a cabinet and create an arc flash. So it only really simulates junction boxes. As soon as you add equipment into the box, it shields some of the heat and absorbs some of it. This causes the incident energy to drop off a lot. So say with MCC do we calculate the arc flash from an empty bucket (prepared space) or any empty section? Calculating with a section filled with buckets is impossible. Actual MCC tests have arc flash that is vastly less than what IEEE 1584 predicts.

IEEE 1584 is known to way over predict all 240 V and below equipment as an example. NESC says it’s 4 cal/cm2 regardless of other factors. This is based on the highest measured incident energy under the most extreme circumstances (3.2 cal/cm2). The highest incident energy ever measured on a 125 VDC battery system simulation is 1.2 cal/cm2. So not labeling this stuff if you are in an “FR mandatory” plant is well justified, or using the “generic” label.

So do not make the mistake of thinking NEC and 70E are identical. NEC depending on where you are working may be legally required. 70E is a recommendation.
Well explained. Thanks
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
While it is true that NFPA 70E is not an "enforceable" standard, OSHA does REQUIRE that all employers have a written policy/program of electrical safety, that all employees are trained on it, and that qualified electrical workers are trained in specific minimum intervals. That program CAN be a "roll your own" policy, but OSHA highly suggests using NFPA 70E as the template.

But here's how it works in reality. IF there is an accident involving electrical equipment and someone is hurt, OSHA will come in and the first thing they will want is a copy of the company's safe electrical work policy, along with records of every electrical worker having received the minimum required training. If the manager / supervisor responds "What policy?", they may end up going to jail (ignorance of the law is no excuse). If you DO have a policy, it had better look an awful lot like NFPA 70E, because that is the standard that OSHA recommends. In other words your company can ignore NFPA 70E at their own risk, including civil and criminal liability. Most companies just find it simpler to adopt NFPA 70E as their policy, it makes OSHA a lot less adversarial if they have to come in to investigate an accident.

Per the NEC though, per 110.16 Arc Flash Hazard labels are required for all panels that are "likely to require examination, adjustment, servicing, or maintenance while energized...", which is basically anything with a breaker, fuse or controller. The label might just say there is no hazard because the kCal is so low, but it needs the label anyway.
 
Last edited:

Electriman

Senior Member
Location
TX
While it is true that NFPA 70E is not an "enforceable" standard, OSHA does REQUIRE that all employers have a written policy/program of electrical safety, that all employees are trained on it, and that qualified electrical workers are trained in specific minimum intervals. That program CAN be a "roll your own" policy, but OSHA highly suggests using NFPA 70E as the template.

But here's how it works in reality. IF there is an accident involving electrical equipment and someone is hurt, OSHA will come in and the first thing they will want is a copy of the company's safe electrical work policy, along with records of every electrical worker having received the minimum required training. If the manager / supervisor responds "What policy?", they may end up going to jail (ignorance of the law is no excuse). If you DO have a policy, it had better look an awful lot like NFPA 70E, because that is the standard that OSHA recommends. In other words your company can ignore NFPA 70E at their own risk, including civil and criminal liability. Most companies just find it simpler to adopt NFPA 70E as their policy, it makes OSHA a lot less adversarial if they have to come in to investigate an accident.

Per the NEC though, per 110.16 Arc Flash Hazard labels are required for all panels that are "likely to require examination, adjustment, servicing, or maintenance while energized...", which is basically anything with a breaker, fuse or controller. The label might just say there is no hazard because the kCal is so low, but it needs the label anyway.
Thanks.

So If we want to implement OSHA and NFPA 70E, what is the requirements (information) as far as AF labels for each voltage level on switchboard, switchgear, MCC, panel boards subpanels and load centers based on the latest edition?
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
... what is the requirements (information) as far as AF labels for each voltage level on switchboard, switchgear, MCC, panel boards subpanels and load centers based on the latest edition?
Effectively the label needs to provide information on the maximum voltage hazard so the worker can select the proper PPE (per your safe work policy). The label needs to provide the AF incident energy level, again so the proper PPE can be chosen. There are a few other mandatory items and some suggestions, but actual specific layout and content is up to your company.

All workers need to be trained in how to read the label and it should be explained in your safe work policy.
 
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