On Mon, 16 Jan 2006 12:02:15 GMT, (Beachcomber)
wrote:

On Mon, 16 Jan 2006 06:03:42 -0500, "Bob" wrote:

If you secure only one wire to each screw, I don't believe it's possible to
short anything out. There is nothing internal in the design of a three-way
switch which would cause a short. (Take a look at the schematic in komobu's
link.) Secure the wires to the new switch, but let it hang out of the box
where it isn't touching anything. Turn the breaker on. Then put gloves on
and check the new switch to make sure it's wired correctly. If it is, turn
the breaker off and install the switch in the box. Then turn the breaker
back on. If your system is grounded and the new switch is hitting something,
your breaker should trip.


Make sure you understand exactly what you have there. If there are
four control points, then it is most common to have two three-way
switches (3 terminals on each) and two four-way switches (4 terminals
on each). Each extra control point may be installed using an
additional 4-way switch.

The four way switch acts as a kind of reversing switch to the two
traveler wires which are terminated at each end by the three-way
switches.

Three way (and four way) switches are mis-named but no-one ever
bothered to change the term for a better understanding of common
electrical use. A three way switch is more correctly termed a Single
Pole Double Throw switch (SPDT). Why then, is it called a three
way switch? Because it has three terminal screws on it?!

I heard it was because when such a system is installed, wires are run
to 3 places (for the 2 switches and the light).

Very
strange.


A 4-way switch could be DPDT with opposite terminals connected
internally. I'm not too sure of this, but have seen such for reversing
a small DC motor (where run direction depends of polarity).

Another mis-named electrical device.... The Current Tap.

Beachcomber

--
Mark Lloyd
http://notstupid.laughingsquid.com

"Democracy is two wolves and a lamb voting on what
to have for lunch. Liberty is a well armed lamb
contesting the vote." - Benjamin Franklin