Re: why ground an alarm panel.

[w_tom <w_tom1@xxxxxxxxxxx>]

  Every utility entering the building must connect to the same
earth ground rod before each wire (in the cable) enters the
building.  Code even defines a maximum distance for that
earthing wire.  Code since 1990 requires a dedicated earthing
electrode - cold water pipe is no longer acceptable as the
earth ground.

  A building ground system has different components for
different groundings.  They share common parts.  But the
earthing ground is that dedicated earth electrode (typically a
10 foot ground rod) that the building owner provides.
Telephone line protector and CATV wire ground block both make
a direct connection to this earth ground that is also best at
'less than 10 foot' connection from mains breaker box.

  Safety ground is where neutral wire, safety ground wires,
and connection to earth ground all meet in the same box that
contains the main disconnect circuit breaker.

  Water pipe must still connect to breaker box where pipe
enters the building.  This to remove stray currents from the
pipe - not for earthing.  Any wire that dumps current into
pipes is no longer acceptable.

  Figures from one utility demonstrate the concept of earth
grounds - wrong (bad), right, and preferred.  Notice all earth
grounds should be common - if necessary by buried a bare
copper wire that interconnects all earth grounds.  This
required for human safety and also provided for transistor
safety:
   http://www.cinergy.com/surge/ttip08.htm

  Why might the telco and cable drive their own rods?  Because
the building owner did not provide that essential single point
earth ground.  Protection of a panel is defined by the quality
of earthing and connections to it.

  Comments from Robert Bass are also important in protecting
panel electronics.  Multiple ground systems share common
components (ie wires).  One system is earth ground.  Other is
safety ground.  Earthing electrode performs both human safety
and transistor safety functions.

  BTW, why do some jurisdictions now require a dedicated
ground wire to steel bathtubs?  For same reasons that others
have posted about using pipes for grounding.  Wire to pipes is
only to remove electricity from those pipes.  No longer
acceptable (post 1990) to ground to pipes with intent of
dumping electricity into those pipes.

Mike Sokoly wrote:
>          does not permit you to "share" others' ground rods.
>          When in doubt- drive your own ground rod.
>          Note: Telco and cable TV Co.s USED to drive their own rods!