Make a Tight Connection Between Stranded and Solid Wire
To install smoke alarms, light fixtures or dimmer
switches, you usually have to connect solid wire to
“stranded” wire, which is actually a bundle of tiny wires.
Often, the wire connector doesn't grab the stranded wire
but just pushes it down, creating a poor connection.
Here's how to make a reliable connection: Strip off extra
insulation so the exposed stranded wire is about 1/8 in.
longer than the exposed solid wire. Then twist the strands
together and screw the connector onto both wires.