NFPA 70E Hazard Risk Catagory

[Data Center Electrician]

There is some confusion in the workplace about the tables 130.7(C)(9). We have clearly marked labels in some areas above catagory 4 up to 100+ Cal/CM2. Other areas lower. Some people feel that these labels can be overruled by this table. Example: 600 V Class switchgear. Voltage testing. Listed as 2*. Tell me why this isn't above a catagory 4 if the sticker says above catagory 4? Thanks.

 

[jim dungar]

The 'task tables' are only used if a study has not been performed. Once the cal/cm? have been determined, the tables are no longer applicable.

 

[eric7379]

There is some confusion in the workplace about the tables 130.7(C)(9). We have clearly marked labels in some areas above catagory 4 up to 100+ Cal/CM2. Other areas lower. Some people feel that these labels can be overruled by this table. Example: 600 V Class switchgear. Voltage testing. Listed as 2*. Tell me why this isn't above a catagory 4 if the sticker says above catagory 4? Thanks.

Did you do an arc flash analysis/ hazard risk study? If so, then you CANNOT use the tables, as Jim mentioned.

Actually, now that I think about it, if you do a study and then determine that the calculated cal/cm2 is lower than what the ratings are for the task tables, then I think that you can still use the task tables. I might be wrong about this. I don't have a copy of the 70E in front of me. If I am wrong about this, I hope someone else chimes in with a correction.

But here's the catch-22 of it all. You can't just outright say "we are going to use the task tables" because in order to use the task tables, you need to determine (i.e. a mini-analysis) whether or not you even qualify to use the tables. If you don't qualify to use the task tables, then you have to do the analysis/study. IMHO, you would be better off with just doing the analysis/study and be done with it.

My own personal opinion is that the task tables be done away with. I have my reasons for it.

 

[zog]

There is some confusion in the workplace about the tables 130.7(C)(9). We have clearly marked labels in some areas above catagory 4 up to 100+ Cal/CM2. Other areas lower. Some people feel that these labels can be overruled by this table. Example: 600 V Class switchgear. Voltage testing. Listed as 2*. Tell me why this isn't above a catagory 4 if the sticker says above catagory 4? Thanks.

Other guys are right in saying you can't gp back to the tables. Few comments:
1. You have identified the Ei from an analysis using real data, you go back to a table that uses a lot of assumptions to give you a lower HRC than your calulated value is ignoring the hazard you have already identified and if someone would become injured your company would be found negligent, seen it in court myself as a expert witness.

2. If you have calualted Ei of 100cal/cm2 you won't be able to use the tables anyways, your clearing times and/or fault currents are outside the limits of the tables. Whoever is telling you to use the tables over the stickers dosen't understand the application limits of the tables.

 

[Data Center Electrician]

NFPA 70E Ongoing effort

NFPA 70E Ongoing effort

Thanks for the input. This is an ongoing effort where we are trying to make sure that everyone understands the 70E. When people are used to getting the job done and not used to limits or constraints being set on their procedures it is easy to understand how they might read things into the 70E that do not apply.