[TowerTalk] Ground system design, RF vs AC

[Keith Dutson]

>If you cross-connect your ham & AC power grounds, any such fault currents
will flow in your ground system too, for better or worse.

AFAIK, every piece of ham gear that uses a three prong AC cord has the
safety (green) wire securely attached to the chassis.  If you attach a
ground strip from the chassis to the ham system ground, does this meet your
definition of "cross connect"?

Keith NM5G

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Martin AA6E
Sent: Friday, February 25, 2005 3:11 PM
To: keith at dutson.net; towertalk at contesting.com
Subject: Re: [TowerTalk] Ground system design, RF vs AC

Keith,

I believe "fault" is the general electrical term for power going where it
shouldn't.  That's why we have protective system grounds in AC systems.  If
there is a short circuit in an appliance connecting the hot side to the
chassis, a fault current flows in the ground lead and the user is protected.

A GFCI detects even tiny fault currents and shuts off the circuit asap.
(It detects a difference between hot & neutral current, as you
suggest.)  That's a good thing, but old-fashioned fault protection involves
blowing the upstream fuse or breaker with an overload current.
 That's one reason why your branch circuit wiring has to be matched to your
breaker - to be sure it will trip quickly if there is a short.

If you cross-connect your ham & AC power grounds, any such fault currents
will flow in your ground system too, for better or worse.

-Martin (who is not an electrician)

--- Keith Dutson <kjdutson at earthlink.net> wrote:

> You wrote:
> >The problem with connecting the AC green wire to the radio room
> ground and
> then connecting my bulkhead "SPG" to a new ground rod or even a 
> perimeter ground connection is that my radio installation becomes part 
> of the AC protective ground system for the house.  That is, any house 
> fault or other current will partly be routed through my radio ground 
> system. Is that what we want?
> 
> When you say "house fault" I assume you are referencing a ground  
>fault  circuit interrupter (GFCI) system.  Such a system interacts with 
>the  white  neutral ground, not the green safety ground.  So the answer 
>is yes,  we do  want the safety ground connected.
>...
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