Chris Eller wrote:
Doug Miller wrote:

In article , Chris Eller wrote:


Something that may make this a moot point; mt main electrical box has bonded
neutral and ground bus-bars. So, any improvements I make up the line won't
really help as the box is old design. Probably have to replace the box as
well.

An I on target here?


No. Your main panel is just fine. The NEC *requires* the ground and neutral
bars to be bonded at the main panel, and *prohibits* *any* connection between
ground and neutral anywhere else.


Definitely good to know. What I really need to do is take a few classes and
learn to not only read, but _understand_ the NEC.

As I understand it, the NEC changed the bonded N and G around the time my home
was built (1965), so somehow my stove was wired up with three conductor:
H,H,N/G. Would you say that running a new 4-conductor (H,H,N,G) line to the
stove would be beneficial? I certainly think it would be an improvement, but
is it necessary?

Thanks,
Chris

Let's review what happens when the neutral goes open at any point in the
circuit between the panel and the stove. The stoves 120 volt loads will
serve as rather low resistance conductors between one of the
ungrounded conductors and the frame of the stove. Another poster has
alleged that that is not a problem because you will be in series with
the load. When two impedances are in series the largest quantity of the
voltage will be reflected across the higher impedance. In the circuit
in question the higher impedance is the human being. If the voltage
applied across that human being is higher than 30 volts there is a
likelihood that that person may be injured or killed the only thing
missing is contact with another conductive surface that happens to be
grounded. The kitchen sink, refrigerator, dishwasher, and even many
kitchen floor coverings are sufficiently conductive to provide that
conductive pathway.

It has also been alleged that it makes no difference because both
conductors terminate on the bonded buss bar of the service equipment
enclosure. That position ignores the fact that since the neutral
conductor carries current it expands and contracts with each use of the
appliance. As a result of that normal thermal cycling it's connections
are under far more stress than those of the equipment grounding
(bonding) conductor.

In the older three wire configuration any failure of the neutral
conductor energizes the frame to the potential of the circuit. In the
four wire configuration the neutral opening causes the appliance to stop
functioning but the frame will remain at zero volts relative to other
grounded surfaces.

I'm only one member of the entire nations fire service and I have
attended three accidents that were secondary to failure of neutral
terminations on three wire appliances. It is true that I have been in
active service for thity plus years. One was an electrocution. the
other two were electrical injuries that were short of being fatal. One
was a working code who then spent weeks in the hospital and was provided
with an implanted defibrillator while her injured heart muscle healed.
The other suffered a dislocated shoulder and a fractured arm as a
secondary effect of the severe muscle contractions that occur during
electric shock. In all three cases the appliance in question was an
electric clothes dryer were the frame was bonded to the neutral.

It is your house and your family so which one do you think is better.
--
Tom H