On Fri, 17 Jan 2014 13:52:41 -0600, SteveF wrote:

On 1/17/2014 12:57 PM, (PeteCresswell) wrote:
Per Stormin Mormon:
Though, others would see the metal
work boxes, and insist on grounded 14 AWG
Romex. Sigh.

At the risk of sounding inane - but just to be sure - the reason for
grounding the metal boxes is to protect somebody touching the box from
electrical shock in case one of the hot wires contacted the box.... have
I got it right?


A short in the box will trip the breaker. The primary reason to do so
is to prevent a fire. "You" creating a path to ground will not trip
a breaker. A GFI breaker on the other hand...

The NEC has different methods of protection. Not all are for a human,
directly.
No, a short to the UNGROUNDED box will NOT trip the breaker - which
is why the ground is required. A ground does virtually nothing to
prevent fires. It prevents shocks from touching the box even if there
is not enough leakage to blow the breaker. You could have a high
resistance short that could supply 1 amp of current to ground through
the box - if ungrounded and you (grounded) touched it, it could kill
you. With it grounded, even though there is not enough current to trip
the breaker, it is held to ground potential, ensuring you will not
recieve a dangerous shock should you inadvertently get between the box
and ground.