Should solid copper or stranded copper be used with the pressure terminals of a duplex receptacle?

Either one can be used. Electricians prefer to use a solid wire and use the screw terminals rather that the pressure terminals. An eyelet can be formed with solid wire where as using stranded wire takes a bit more preparation to use. The stranded wire has to be wound tighter at the termination end. This is so that when the stranded wire is tightened under the screw terminal the wire does not splay into individual strands some of which do not get under the terminal screw. With some of the strands not tightened under the screw, this is the same as using a smaller size wire. The breaker feeding the receptacle is matched to a specific wire size. The now smaller wire size has a breaker greater than the ampacity of the wire. This could lead to overheating of the wire under full load and eventually cause a breakdown of the insulation. Once the insulation has broken down, the breaker will trip due to a short circuit. This wire will have to be replaced. This could involve opening the wall board to remove the burnt wiring should this happen.



Most residential wiring is done with solid copper wire. In industrial applications, stranded THHN wire is used because many wires are run through conduits from service boxes and many different colors and gauges can be run to different locations. I personally would not use stranded in a residential application.