Voltage levels for category rating

Status
Not open for further replies.

Chev

Master Electrician @ Retired
Location
Mid-Michigan
Occupation
Retired Master Electrician, Formerly at Twin Lakes Electric and GMC
I found out today that NFPA 70E Table 310.7(c)(10) 2009 says we have to wear a balaclava and face shield for category 1 "live" work and it needs to be a 4 cal. face shield, category 2 needs to be an 8 cal. face shield. I have no difinative listing for the voltages and am assuming that >50-<240 would be category 1 >240-<600 would be category 2. Where would I find if I'm right or wrong?
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
You are confusing the danger of coming into contact with an energized metal component with the danger of being in the vicinity of (but not necessarily in contact with) an energized component that experiences a short circuit event that engulfs the surrounding air in a fire ball (i.e., an "arc flash" event). The voltage level will tell you the minimum distance you must remain away from energized components, unless you have been trained and qualified to work on live parts, and have received the proper permissions to work on live parts, and unless you are wearing the proper insulating clothing. Separate from that consideration, the amount of arc flash energy that the component is capable of releasing will determine the arc flash catagory, and that will establish the minimum protective clothing needed to approach the component.
 

Chev

Master Electrician @ Retired
Location
Mid-Michigan
Occupation
Retired Master Electrician, Formerly at Twin Lakes Electric and GMC
Sorry Charlie, but that is not what I was looking for. PPE is determined by the voltage and amperage where I'm at, and I need to be able to put it in simple terms for the masses here.
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
I agree that voltage level has a bearing on the minimum PPE requirements. Amperage, however, is absolutely irrelevant. But your question used the terms "category 1, category 2" and "calories." Those terms are related to arc flash, and the voltage level does not determine the category or the PPE requirements. You can have a 4160 volt board that has a "category 0" (lowest level) arc flash risk, and you can have a 208 volt panel that has a "category 4" arc flash risk.
 

Chev

Master Electrician @ Retired
Location
Mid-Michigan
Occupation
Retired Master Electrician, Formerly at Twin Lakes Electric and GMC
Therein lies my problem Charlie, every floor level SQ-D enclosure in this plant is labeled category 0, but that is with the door closed and properly latched. That is in a range from 120/208/240-125 amps through 480 volts 400 amps. They can't all be cat. 0 with the covers off, so I'm as confused as the day is long!
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
First lets get some focus.

Did you have a professional arc flash study done or are you trying to use the 'task tables' in 70E?

Have you had any instructor led training on 70E?

Does your facility have a written Electrical Safe Work Practices program that is based on the current edition of 70E?
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
. . . every . . . enclosure . . . is labeled category 0, but that is with the door closed and properly latched.
I would be surprised if the label actually said that the category 0 only applies with the door closed and latched. Are those words actually written on each label? If so, I would be inclined to guess (and it is only a guess) that the labels were installed at the factory, and are not based on an arc flash calculation (as Jim alluded to).
They can't all be cat. 0 with the covers off
Well, actually, yes they can. I don't know if they are, but it is not impossible for them to all be category 0. Everything depends on such factors as the impedance of the incoming source transformer and any step down transformers, the sizes and distances of the various feeders, and most importantly the settings of the overcurrent protection devices. Without a formal calculation, it is not possible to know for certain.


 

Chev

Master Electrician @ Retired
Location
Mid-Michigan
Occupation
Retired Master Electrician, Formerly at Twin Lakes Electric and GMC
Did you have a professional arc flash study done or are you trying to use the 'task tables' in 70E? I'm not sure, but I think they used the tables

Have you had any instructor led training on 70E? No

Does your facility have a written Electrical Safe Work Practices program that is based on the current edition of 70E? No, I'm the site trainer for ESWP and I got my training in 2008 which was based on 2004 70E. They just ordered me a copy of 70E for 2009. I'm waiting to see when they will come up with a refresher, but I'm also not wanting to wait for them to get a course going.

I'm pretty much on my own, and I'm learning as I go. Prior to my taking this position things were pretty sloppy around here, I'm trying to get them to follow the NEC 70, and also 70E, OSHA, AND NFPA 79. It has been a slow process with me dealing with 4 different salaried "safety reps" with different agendas over the last 2 years. I finally have one who wants to do the right thing, coupled with an EE who also wants to turn this place around.

Charlie, Those are factory labels. What I'm doing is taking the survey information and making ESWP labels with the necessary info on them for the PPE and boundaries.
 
Last edited:

zog

Senior Member
Location
Charlotte, NC
Chev, please don't take this the wrong way but your posts show some misunderstanding of the requirements and basis of PPE. If you are the ESWP trainer at your facility you really need to get some "train the trainer" training, I used to offer these in Michigan but no longer do that stuff but I can recommend some people if you like. I understand the difficult position you are in, seen the same thing many times.

The other guys addressed your questions already, keep in mind there are 2 types of PPE, shock and arc flash. Shock PPE, such as rubber gloves will be dependant on voltages, but arc flash PPE has little to do with voltages. If your facility used the tables there should be different HRC's for doors open and closed and different tasks, which makes it all confusing for the operator. The limitations of the tables changed with the 2009 70E so that should be looked at and many of the HRC's from the task tables changed also.

Your best bet it to get some good compliance training, sounds like your facility needs to start from square 1. Again, I really don't want this to come off the wrong way and will be happy to help, as will many others here.
 

Chev

Master Electrician @ Retired
Location
Mid-Michigan
Occupation
Retired Master Electrician, Formerly at Twin Lakes Electric and GMC
Thanks zog, my training was very limited, I figure you know where I got it. Questions I have been asking are as you imply...no offence taken, my ego isn't that big!:)
 
Status
Not open for further replies.
Top