Maybe - If your equipment is grounded via the green AC wire (third pin)
AND to a separate ground, then you have to expect some current will
flow from one "ground" to the other under various fault or surge
scenarios.
A lot of rigs now don't have a 3-wire power connection, but rely on
external 12 volt supplies, whose outputs could be floating with respect
to the AC third wire ground. Potentially (no pun), that's a good thing
if you want an isolated system.
My old TS-520S has a 2-wire AC cord, which I always thought was the
right way to do it, if you can trust the user to attach his/her own
ground system.
73, Martin
--- Keith Dutson <kjdutson@earthlink.net> wrote:
> >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@contesting.com
> [mailto:towertalk-bounces@contesting.com] On Behalf Of Martin AA6E
> Sent: Friday, February 25, 2005 3:11 PM
> To: keith@dutson.net; towertalk@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@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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