Adding a sub-panel
So i just had my 6 fuse panel upgraded to a 100 amp 20 breaker panel. Upon finishing my electrician tells me that he ran out of breakers and he wished he added a 30 as he short a few circuits. He also mentioned that he is retiring on the 16th and I am going to need someone to add a 60 amp sub panel for the remaining circuits. The way it turned out, the previous owner had 6 fuses with multiple upon multple wires going to each one.
He said it was easy to add the sub panel and based off what he has seen me do that I could do it, just remove two single breakers add a 60 amp breaker and then run that wire to a sub panel with 10 more slots.
My question is, is it that easy? I'm pretty confident with electricity and want to attempt this project but i want to get all the info I can before I do it. Any tips, suggestions, precautions? Thanks