Re: protection

["Robert L Bass" <robertbass1@xxxxxxxxxxx>]

> Most critical is that the earthing be single point.
> Every incoming wire must earth to the same
> earth ground.  Each structure must have its
> own single point earthing...

Very true.  If every incoming service on the structure is connected to a single point ground there is a significant reduction in
damage from lightning.  This is particularly important for sensitive electronics such as security and home automation systems.

Unfortunately, even when the installer correctly earth grounds the alarm, his system may still be unprotected if other tradesmen
don't follow code.  In many areas the worst offender is the CATV company.  They were notorious in New England and they still are in
Florida for failing to ground at all, grounding improperly to metal siding, piggy backing onto the electric panel ground, etc.

I routinely discuss bonded grounds with DIYers, especially on new construction.  Just as with propfessionally installed systems,
other tradesmen are often at fault.  Most electricians get it right but plumbers, CATV and even some telco installers screw up.  I
also noticed when I first brought the subject up in this newsgroup some years ago that some alarm techs are unaware of the
importance of a bonded (aka single point) ground.

On a related subject, it bears repeating that the panel ground needs to be as short as possible.  Bends in the ground cable should
be radiused -- no hard 90 degree turns.  The best connection point it a ground rod sunk into the earth.  Never ground an alarm panel
using an electrical outlet ground.  There are a few plug-in transformer which include a ground terminal.  Do NOT use that terminal.
It will not provide proper protection for the alarm system's electronics.

Mike Holt has useful information on grounding, bonding, etc., on his website at mikeholt.com.  Note that most of his information
concerns safety grounding (keeping people alive) whereas the primary concern for alarm installation is protective grounding (keeping
electronics alive).  Nonetheless, it's a very helpful website.

--

Regards,
Robert L Bass

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