Calvin Henry-Cotnam wrote:
Doug Miller ) said...

In article . com, "stretch"

wrote:

Ken,
If you use a ground wire for neutral current and a ground fault
happens, It may not be big enough to carry both ground and neutral
currents.

Nonsense.


Definately nonsense -- the neutral has to be the same size as the hot
conductors, so the current capability has to be there with the neutral
alone.

The issue with grounding something with the neutral is that since the
neutral carries a current, and since conductors are not "perfect" (i.e.:
they do not have zero resistance), a voltage drop will occur. Depending
on the load current and the length of the cable run, any neutral-bonded
piece of equipment will not be at ground potential, but a few volts away
from ground. In the right circumstances, contact with this and something
that is at ground potential could be very dangerous.

BZZT Wrong. The neutral can be sized for only the worst case of current
imbalance which is the failure of one leg of a split single phase
service or of one phase of a three phase service. Loads that run at the
end to end voltage of a single phase service or phase to phase of a
multi phase service need not be included when calculating the required
ampacity of the grounded current carrying conductor (neutral).

The real risk of bonding the exposed conductive frames of appliances to
the neutral is that if the neutral goes open the voltage on the frame of
the affected appliance/s will rise to the voltage to ground of the
supply source.
--
Tom H