On Thu, 15 Jan 2009 23:12:14 -0500, "Buerste" wrote:


"Tman" wrote in message
...
Took a look at the schematic today for the dryer (240v). I've always
wondered how they serve up 240 V with 120V components (e.g. timer motor)
on only three wires.

You see, I always thought that the grounded conductor should never be
current-carrying, in the theory that if the ground feed should break, then
the metal chassis of the appliance does not get energized.

Well looks like that "3rd" wire, is a neutral, and judging by the dryer
schematic, is both used as a chassis ground and a current-carrying
conductor for the 120V items on the dryer -- such as timer and drum motor.

OK -- am I totally wrong about the code and theory, or is this unsafe?
Seems to me that dryer would get real "hot" should their be a fault in the
neutral conductor to the breaker box.

I know I'm missing something here as this is SOP as far as I am aware.
Someone please inform me?
T

Google: "Split Phase"
In a nutshell, the two hots are 180 degrees out of phase with each other.
The potential between either phase and ground/neutral is 120v. The
potential between the two hots is 240v. A single phase of Alternating
current looks like a sine wave on an oscilloscope with the wave swinging up
and down. With split phase, it looks like 2 waves on the scope. As one
wave is bottoming out the other is topping out. They are like mirror images
of each other. If you measure the peak of either wave to ground, it is
120v

Actually, the peak is 170V (RMS * 1.414) but you don't need reality to
get in the way here :-)

if you measure the top peak of one wave to the bottom of the other, it
is 240v.

340V. Shut up, reality :-)

There, clear as mud! Any 240v device will run on just the two
hots, any 120v device will run on either hot and ground/neutral.