I have ran into several conductors that are old enough that the size can not be read on the insulation. How do you tell what size the wire is? I am unable to disconnect and actually measure it.

One method is to assume that the conductor is sized properly for the protective device it is connected to (or vice versa). Then knowing the length of the conductor, you can input one size up or down in the software and see how much of a difference it makes on the arc flash. This will of course not tell you if you are code compliant for protecting the conductor.

That is what I am doing now, but with the age of the plants I am responsible for, assuming code compliance is a stretch.

I understand that but just document your assumptions and I think for the most part even going up or down 2 sizes will not make significant difference.

Why do you think that?
What percentage of your identified conductors have been misapplied?

Another option is to purchase a set of non-metallic digital calipers and measure the conductor diameter. Then you look up the conductor diameter and make a logical assumption of the wire size. This will at least give you a pretty sound basis for your assumptions and you should be able to identify conductors that are not protected in accordance with the NEC. We did this for several old plants and the work goes pretty quickly. In our case, all of the measurements were made with the 40 cal. flash suit on due to the nature of the work and the location of the measurements. Some areas will be too dangerous to do this type of work, even with the 40 cal. suit.

Thank you.
I understand a size up or down has the potential to make very little difference, but it goes against my perfectionism. I put in a request for some non-conductive calipers.
Again Thank You

I can understand that but I don't like the risk with sticking something into a panel and then you risk the possibility of encountering a loose wire and possibility creating an arc flash.

If you can de-energize the circuit, you could use a very handy device called a "Wire Mike". It is a "Burndy" product. Part # RK194-2. I have carried one in my tool pouch for years.

I would consider removing and replacing the conductors if the insulation is old and has deteorated.

WBD, I agree that you must be extremely careful when doing this type of investigation. We weren't checking small gauge wires that are more likely to come loose. These were large gauge conductors in switchgear with visibly well-crimped lugs. We were also very careful to measure the cables in a manner where we didn't have to disturb their positioning. That said, Steve makes an excellent point; deenergizing is your safest bet!