mayanees
Senior Member
- Location
- Westminster, MD
- Occupation
- Electrical Engineer and Master Electrician
Hah!
Hah!
Bingo Doug. That's the same rock that hit me a couple months ago, but I think I've developed a reasonable position statement.
Your reported 160cal/cm^ which is huge given that an HRC4 PPE is listed at 40 cal, but it's not uncommon for the secondary of a 480V, 2-3 MVA transformer.
To further complicate your situation, that label has been posted. You can't go to NFPA 70 table 130.7(C)(9) to determine the appropriate PPE to wear to adjust the meters now. The incident energy has been calculated. One could make the argument that the Arc Flash Boundary (AFB) of 29.7 feet can not be safely entered into without PPE at any time.
But the fact of the matter is that with the doors closed, it won't be Arc Flash that hits you, it'll be flying debris or plasma!
And there's no calculation that I know of to tell you what to wear to protect from that.
The saving grace, IMO, is that NFPA 70E dictates that that label applies when interacting with electrical equipment. Certainly with the covers off, all the numbers apply. But with covers on, there's no need for Shock protection, so it's down to worrying about that AFB number.
The final piece of data that rationalizes our coexistence with electrical eqiupment is that there must be an Electrical Safety Program (ESP) that makes everyone in the facilty aware of the dangers listed on the label.
What that should do is force ownership of the situation, with development of practices to avoid the potential danger area. For example, if that label you've listed is for the inside of a 480V, 2500 kVA transformer, realize that there's a 30 foot AFB, and avoid occupying that area.
If it's the secondary of a PDU in a Data Center, respect the boundary (in this case it may be a 10 foot AFB) by not having a desk in that space.
There are many systems out there that have these kind of Hazard Risk Category (HRC) levels, and when an ArcFlash Analysis gets performed, and they implement the ESP, will logically rearrange their layouts to accommodate.
I don't expect there to be a prevalence of Arc Resistant 480 V gear because it must be built like a tank in order to contain the blast. That makes it too epxensive compared to other options, like: smart equipment layout; design limiters; etc.
John M
Hah!
-------------------------------------------------------------------------Well now ya'll went and turned over a rock...
The breaker shown is one of two mains, load side of my buildings sub's...
The warning label reads....
356 inches Flash Protection Boundary
160 cal/cm^2 Incident Energy at 18" Working Distance
Dangerous! Exceeds NFPA 70E-2009 PPE Categories
480VAC Shock hazard when cover is open
42 inches Limited Approach
12 inches Restricted Approach
1 inch Prohibited Approach
The fun begins...
For these OCPD on/off, do I need a 1" stick and a bomb suit, or a 30 foot stick and I can switch them in my skivvies... ?
I've got some reading to do...
Thanks,
Doug S.
Bingo Doug. That's the same rock that hit me a couple months ago, but I think I've developed a reasonable position statement.
Your reported 160cal/cm^ which is huge given that an HRC4 PPE is listed at 40 cal, but it's not uncommon for the secondary of a 480V, 2-3 MVA transformer.
To further complicate your situation, that label has been posted. You can't go to NFPA 70 table 130.7(C)(9) to determine the appropriate PPE to wear to adjust the meters now. The incident energy has been calculated. One could make the argument that the Arc Flash Boundary (AFB) of 29.7 feet can not be safely entered into without PPE at any time.
But the fact of the matter is that with the doors closed, it won't be Arc Flash that hits you, it'll be flying debris or plasma!
And there's no calculation that I know of to tell you what to wear to protect from that.
The saving grace, IMO, is that NFPA 70E dictates that that label applies when interacting with electrical equipment. Certainly with the covers off, all the numbers apply. But with covers on, there's no need for Shock protection, so it's down to worrying about that AFB number.
The final piece of data that rationalizes our coexistence with electrical eqiupment is that there must be an Electrical Safety Program (ESP) that makes everyone in the facilty aware of the dangers listed on the label.
What that should do is force ownership of the situation, with development of practices to avoid the potential danger area. For example, if that label you've listed is for the inside of a 480V, 2500 kVA transformer, realize that there's a 30 foot AFB, and avoid occupying that area.
If it's the secondary of a PDU in a Data Center, respect the boundary (in this case it may be a 10 foot AFB) by not having a desk in that space.
There are many systems out there that have these kind of Hazard Risk Category (HRC) levels, and when an ArcFlash Analysis gets performed, and they implement the ESP, will logically rearrange their layouts to accommodate.
I don't expect there to be a prevalence of Arc Resistant 480 V gear because it must be built like a tank in order to contain the blast. That makes it too epxensive compared to other options, like: smart equipment layout; design limiters; etc.
John M
