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Re: Double-pole single toggle switch vs. 3-way switch?


John Gilmer

Jan 1, 1970
East Coast said:
I have looked in a couple of wiring books and I don't see double-pole
single toggle switches addressed. What is the difference between a
Double-pole single toggle switch and a 3-way switch?

A Three-Way switch is identical to a SPDT switch in every respect. If they
are listed separately it might be because one is generally intended for a
particular application.

The three say switches are routinely used in homes to permit, for example, a
hall lighting fixture to be controlled from both the top and the bottom of
the stairway. Any "home center" type store will carry this type of switch.

Double pole (DPST) switches are ofen used to switch 240 volt loads (I use
one at my water heater as a "vacation" switch.) These switches are also
carried by Lowe's and Home Depot type stores.

There is another switch call the Four Way switch. Internally, it is a DPDT
switch which is internally connected as a 2 pole reversing switch. The
4-way switch is used in combination with 2 three way switches (above) to
switch a light fixture from 3 separate locations. Actually, you can add
as many 4-way switches as you care and any switch will turn the light on or
off. These switches (4-way) are a little harder to find but they are out

A true DPDT switch with reasonable ratings (240 volts, 20 amps) is hard to
find. They have an obvious application is switching a load between two
power sources. When sold as "transfer switches" they are quite expensive.
Some power panel makers use mechanical interlocks to cause two circuit
breakes to act as a transfer switch.

I see in the
Leviton catalog these are two different items.

If you have a single light, like in a hallway, and want to be able to
switch it on and off from two different locations, you use a 3-way
switch I've been told. How is a double-pole single toggle switch used?

The 4-way (reversing switch) is placed BETWEEN the two 3-way switches.
Operation of the 4-way has the same effect as operating one of the 3-ways.
As mentioned above, you can put in a many 4-ways as you care.