I am going to be renovating the kitchen in my home that was built in 1959. Last year I had the main service box replaced and now I have plenty of room for new circuits that I now need. My question is: Can I keep some of the existing runs of the older grey cloth covered NM wire. It is in good condition and is the type with individualy plastic insulated and rubber covered copper wire with a ground. The runs to the refrigerator are 12 gauge and the lights are 14.