This weeks question is actually a continuation of several discussions previously posted on the forum.

How do you label equipment with multiple sources or scenarios such as an Automatic Transfer switch or emergency panels that can be fed from a normal and alternate/emergency source?

• We use 2 labels - 1 for each source
• We use worst case label only
• Label normal source only / live work restricted in emergency mode
• Something else (please describe)

I have done both the Worst Case Label and Normal Source/Live Work Prohibited Emergency Source methods. It depends on the client and the work policies/procedures in place. I think I have only done one where both labels were placed on the equipment. Most facilities don't want that much labeling.

Regardless, the final report always contains the worst case scenario information.

Label the normal source and prohibit work when on the alternate source.

I like to know if this is in 70e or osha about prohibit work when on alternate power sources ? Are these restrictions limit to certain parts of the electrical system , as the service where a generator would be ?

Very often, the calculated IE while on generator is way higher than on utility power, because the available fault current is so much lower that the opening of protection devices is too slow to offer low IE.
So instead of having two labels on the same electrical equipment (one for the IE while on utility power, the other while on generator), some AHJ will decide to prohibit live work while on generator power to lower the exposition of their personnel.
To my knowledge, it's not a 70E or OSHA requirement, but an arguably good judgement call by some AHJ.

Worst case.