In a message dated 10/20/2005 8:23:04 A.M. Eastern Standard Time, francis.carcia at hs.utc.com writes: Does the NEC permit connecting Cu wires with Ag-Sn solder? NO.....soldering is not allowed. exothermic welding is, but truely, a good marrying of the wires and a wire nut is a very good connection. DON'T solder them, if anything goes wrong, it is a violation.