100-ohm and 200-ohm resistor in parallel across 120V.
Current through the path of least resistance = 1.2A
Current through the 200-ohm resistor = 600mA
Since this (200-ohm resistor) is not the path of least resistance,
practical people WILL NOT be electrocuted :-)
BTW, I did not calculate 1 / ((1 / R1) + (1 / R2))
LOL, OP here. I took a couple EE courses when working on my MS
aerospace engineering and did an internship where I designed one of the
lightest 400Hz DC-AC inverter for aerospace use. I get the split phase,
peak / RMS business quite fine. I'm just not totally up to speed with
what's code and what's not -- and this rig seemed to be amiss.
I guess in the name of being pedantic, I'll point out that the two hots
probably are not exactly "180 degrees" out of phase and "mirror
images" of each other; close but in real life situations the reactive
loads will not be [perfectly] identical across both phases, making the
out-of-phase, well just a little bit different than pi radians :)
What you are calling two hots are comming from a center tapped transformer.
There is only one phase. They can not be out of phase with each other by
any ammount not counting a couple of inches of wire from the transfromer
windings to the load.
Think of the extreme where one H-N has a purely resistive load, and the
other H-N has a highly reactive (say inductive) load, and remember that
both the transformer and the wires have an inherent inductance. The
voltage peaks as measured at the load will not be exactly 180 deg out of
On Sun, 18 Jan 2009 22:04:22 -0500, "Ralph Mowery"
It depends on your point of reference. The normal point of reference
(for wiring on the transformer secondary) is in the MIDDLE
(center-tapped coil). Points are measured from that. That is, 2
What may be confusing to some, is these 2 phases are not 2 of the 3
phases being supplied to the transformer.
The wiring comming into a normal house in the US is single phase. Not two
phase. True two phase power has the phases 90 deg out instead of the so
called 180 deg .
Two phase powe can be made from a 3 phase circuit, but it requires more than
a simple center tapped transformer the normal house has.
On Mon, 19 Jan 2009 19:13:57 -0500, "Ralph Mowery"
The problem with that is that "phase" already means something.
Something that applies equally well to your (I mean the 90-deg apart
one) 2-phase system, 3-phase power, and the normal system used in
houses. Measurements are made in reference to a common point (ground)
which is in the middle of that (residential) transformer. Measuring
the ends of the transformer with a dual-trace scope will show TWO
PHASES. In this case, one leg will show 90 degrees (most positive)
while the other leg will show 270 degrees (most negative) at the same
time. That's two different phases.
At one time the National Electrical Code (USA) allowed 120/240 volt
ranges and dryers to have a shared grounding and neutral conductor if it
was being fed directly from the service equipment. Because of the
potential danger with an open neutral, the Code now requires four wires.
This used to be permitted on residential dryers and ranges on the assumption
that the robust connections would be properly made by a qualified installer
and very unlikely to come loose. This was in the time before 120V grounding
receptacles and small appliances were not grounded. There were (are?) some
dryers with a center tapped heating element to provide the 120V for the
timer. Not a very good design.
It's theoretically not as safe as having separate neutral and ground
wires. But the unbalanced current is very small, the conductor is very
large, and a 240/120V 3-wire circuit is only allowed when connected to
the main panel (not a subpanel), where the ground and neutral are bonded
to the same buss.
If the neutral wire were to inexplicably come loose, I *think* the timer
relay would open and remove power to the drum motor. So the 120V on the
chassis would be current limited by the series resistance of the timer.
(I could be way wrong on this last point)
Oddly enough, the third wire is not a neutral for the main
220 volt heater element. Since the current flows through the
black wires, or black and red. But doesn't need a neutral.
The only time the third wire behaves as a neutral, if there
is a 110 volt timer.
It's a bit strange, but seems to have worked for all these
It was acceptable when installed as others have described, it's no longer
acceptable in NEW installations, but since there aren't piles of
electrocuted housewives across the country, existing installations are still
My house was built in 2000, fwiw.
Also, BTW there is a non-trivial 120v load through that neutral -- not
just the timer motor, but also both main motors (mine is a combined
washer / dryer stacked unit)...
You are quite correct, it was not I that suggested it was only the timer
motor. Clearly there have been few incidents as a result of the wiring
method or the NEC would have demanded it be changed years ago
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