wrote in message
ups.com...
FDR wrote:

Still, if the neutral is broken at the transformer, you still don't
have a
return path.

-----------------------------------------
You really ned to talk to an alectrician. I just asked my electrician
friend
frind and he siad ti is all too common.
OK lets look at it another way.
We have a 240V CT transformer.
Wiht the CT being neultral/ground.
Here we have two wires going from our house to the pole,
that join at the pole witht he center tap.

Actually, three, including neutral. Maybe you are saying it a different
way.


We cut the CT open.
We now have 240V hitting the breaker box. The old neutral
will be somewhere between on side of the 240V and the other.
If the loads are balanced, then it is possible, but not real
likely that you could have 120V across each side, from either
side of the 240V to the centern.
I hope you will agree that 240 devices don't need a newtral return.

I agree with that.


My water heater has the element, a big honking resistor from one
side of the 240V to the other.

Let's put 1 100 watt light bulb on each side of the 240 transformer
in series, with the junction being the house neutral.

Now even without connection to the pole center tap/neutral/ ground
we will ahve 120V across each bulb from common junction of the
bulbs to either side of the transformer.

I see where you are going with that.

I did the math and you are correct.


My electrician friend says that around here, most transformer failures
are caused by severe imbalance between one side of the 240V split
and the other. Around here most transformers have 4 ot 8 homes.
If all of those homes have the same imbalance, "BOOM".
The transformer fails in a ball of fire.

Properly designed installations go to great lengths to match the
current
per leg or phase.

He hates the word phase because too many people confuse the
"2 phases" of the common house transformer with the "3 phases"
of commercial installs. In the typical house your have one transformer,
energised by a single primary and the side of the 240CT are 180
degrees out. In real 3 phase, the phases are 120 degrees out.

Yep.


Draw a diagram of your pole to house circuit.
Showing the ~12KV(varies by area) primary, a 240CT transformer,
witht eh CT being ground or neutral or both, with the 3 (or 4) wires
coming nto your breaker panel. The CT/Neutral/ground forces
the sides to be 120 with refference to the CT. Without the CT, then
the common, broken neutral, will follow ohms law and form a simple
resitive divider. Motoros and non constant loads make it anything
but simple, but just visualise each breaker feeding a differnt
value resistor. Solve each side for parallel value, place the larger
resistance over the lowest and multiply that percentage by the
incoming 240V. It almost certainly won't be 120V. And when a
motor turns on, it really screws things up. The motor can't draw
enough current to get up speed, so it thermals out, and removes
it's self from the circuit. Assume that after some arbitary period
of time every thermal controlled device, fridges, heat pumps, furnace
blowers, are all trying to start and the resulting voltage swings
become very complex.

This is a good way to ruin motors, blow bulbs and is a "real bad
thing."
And it happens.


I got it.