There is an old (1960's) unfused 600 amp disconnect fed with parrallel 500's.
We are looking to replace the switch. I was wondering what type of insulation was used back then. I should send a picture of the wire.
For an amperage rating of these wires, can I use the left coloumb (310.15(B)(16) in the NEC (60c-TW), to play it safe?
I know that table will give it a lower rating, plus I have to derate 70%. It's 6" gal, with 6-500's, and 2-250's for the nuetral.