Martin AA6E wrote:
> 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.
>
This is why the NEC requires ALL ground systems be bonded together.
This is exactly why I said you should run a wire from your new ground
system for the radio, over to the AC original ground system.
> 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.
It is not a good thing if you are looking for lightning protection. You
do not want an additional path to ground at the radio. You would have
one with an arc from radio to AC ground if it is not tied to it.
73
Gary K4FMX
>
> 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.
>>>...
>>
>>_______________________________________________
>>
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
> Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
> questions and ask for Sherman, W2FLA.
>
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>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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