On Aug 25, 9:51 pm, "Percival P. Cassidy" wrote:
The advertising for some wirenuts (don't recall which) says that
twisting isn't necessary. But I have no idea whether it really does vary
from brand to brand.

Let's say wires are not twisted. Then the only reliable connection
between wires is the 'spring' inside a wire nut. If spring wires
makes contact with every copper wire, then no problem. But with heat,
expansion, oxide of copper surfaces, etc, only that wire nut spring
carries most (too much) current. Now the wire nut gets hot and wire
connection create voltage reductions.

Normally that still is not a problem ... if a wire nut 'spring' has
enough turns and makes contact with each wire in enough locations (if
wire nut does not require tape to hold it on wires). Sufficient
connection does not always happen. A hot wire nut is not a code
violation. But you don't want a hot wire nut. Potential for fire or
electrical failure increases.

With copper wire, this rarely causes a fire. With aluminum wire,
this same poor workmanship too often causes fire. See pictures and
technical explanation in:
http://www.inspect-ny.com/aluminum/pl2p8.htm
We don't want wire nuts getting hot even if the manufacture says it
is OK. If wires are twisted together, then all wires touch each other
in multiple spots without a wire nut. Then add a wire nut to make a
good connection better. Wire nut does not get hot by conducting all
current IF wires are properly twisted together.

Wire nuts on copper wire should be properly twisted as if the wire
was aluminum for a best conducting, low loss, no heat connection.

Does not matter whether code requires wires to be twisted together.
All wire connections should be sufficient without the wire nut. Then
we add a wire nut to keep that connection sufficient no matter how
much corrosion or heating might compromise the connection 80 years
from now.