Working on equipment with no arc flash analysis and that doesn't fit in the NFPA 70E tables

I have to access equipment at various customer sites that don't have arc flash analysis so I use the tables to determine the required PPE and I don't access anything that requires PPE higher than Cat 2. I need to connect a power logger to a switchgear that is rated 208Y/120V, 3 phase, 800 amp, 42 kAIC. It doesn't have an arc flash analysis and I can't use the NFPA 70E tables to select the PPE since its AIC rating exceeds 25 kA. I work with electricians that have the "get-it-done" attitude and don't wear PPE unless told to so they aren't any help.

Therefore, I'm trying to find out how others handle this situation. Is it typical to order a full arc flash analysis of the facility before opening up the switchgear? Is there a quick calculation that is typically done in the field? Is there something in between?
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
What does the AIC rating of the equipment have to do with selecting PPE? The 'task tables' depend on the amount of available bolted fault current.

What do you know about the feeder to this equipment.
 
I've always gone by the rating of the equipment since I work on panels without having the short circuit information. Is it typical to do a short circuit analysis on each panel before opening it?

In some locations that's not a simple task.
 

wbdvt

Senior Member
Location
Rutland, VT, USA
Occupation
Electrical Engineer, PE
As noted by Jim, the AIC and SCCR ratings have nothing to do with the parameters of the table in NFPA 70E. You need to determine the actual short circuit current and the protective device clearing time to be able to use the tables. One way to do that is to have a short circuit study done on the system but if that is done, then it would have been easy to do an incident energy analysis.

Another way is to build a simplistic model of the system from the transformer feeding your panel and use 100%, 75%, 50% and 25% of the infinite bus fault current and look at the protective device that would clear that fault and see if under all those conditions, you meet the parameters of the table. Remember that you cannot use the main breaker in the panel you are working on as the clearing device, it has to be the next upstream device, which may be on the transformer primary. If this is the case, I highly doubt that you would satisfy the clearing time parameter in the table.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
It is the EMPLOYER'S or OWNER'S responsibility to provide a safe work environment and instruct EVERYONE on safe work practices at their facility. Ignorance of that is no excuse and they cannot "farm out" the responsibility to outside contractors. Owners, managers and supervisors can be held CRIMINALLY responsible if there is an accident and there was no established safety program. That usually gets people's attention higher up the chain.
 
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