Re: why ground an alarm panel.

["Bill" <bill190nospam@xxxxxxxxx>]

"autonut843" wrote in message
>
>  Why not just use the ground at the outlet?

I have seen building and residential electrical  wiring which could fill a
"horror story" book!

In one case an office building was "rewired" with grounded wiring everywhere
except for one thing. They NEVER connected *any* of the grounds to the main
panel! I am not kidding. (Note the main panel had an excellent cold water
pipe ground and two ground rods spaced 6 ft. apart.) Furthermore there was a
problem with a rooftop A/C unit where it was leaking hot current to the A/C
ducts. And there was a suspended ceiling with grounded (not to panel)
fluorescent fixtures...

So "hot" leaked to A/C ducts, a wire holding the ceiling up was screwed into
a piece of metal which was holding up the ductwork (so hot traveled to
suspended ceiling), then the metal suspended ceiling connected the hot to
the grounded fluorescent fixtures and thus to the entire grounding system
(which was not grounded). So basically every ground in the building was
"hot" along with the suspended ceiling and the ductwork!

Luckily this office did not have any metal grounded office equipment so no
one received any shocks.

But if you were to ground the alarm to this buildings "new wiring", you
would not be grounding it, but would be connecting to a hot. Best to run
your own ground wire back to an electrical service ground rod and use your
own separate clamp. Never trust electrical wiring to be installed properly.

Also as a matter of installing alarms in various buildings of different
ages, by always running your own ground wire, you are always assured of a
good ground and bypass electrical service grounding problems past, present,
and future. Things can happen in the future which disconnect the electrical
service ground. Do as the phone company does. They always run a good ground.

> ...if it were an install in a house from the '50's and you run the new
> dedicated wire from the panel screw to the building's common earth
> ground.   What gauge wire should that be?

At a minimum, I would use the same gauge wire as the phone company ground
wire. Larger if a long run.

> Would the wire need it's own new ground rod, bonded to the other(s)?
> If there is only one ground rod can I clamp my wire on using a new
> clamp?  Or can I just loosen the existing clamp and stick my wire in
> it?

If you are governed by local electrical codes, ask your local electrical
inspector as rules can vary for area to area. Otherwise connect to an
electrical service ground rod using your *own* separate clamp. It would be a
big no no to place two wires in the same clamp.

> If there are multiple rods (a big one for power, a small one for phone,
> a small one for CATV) all bonded together does it matter which one I
> clamp to?

I would use an electrical service ground rod. And if installing your own
ground rod, this would also need to be connected to the other ground rods
using separate clamps. (All ground rods should be interconnected.)