Rik,
In quick scan couldn't find anything on NEC Article 250 supporting your
statement. Did you find anything in 250? I only found a reference to "6 ft
minimum" distance, but that might be old reference and depend on length of the
ground rod. This makes sense for NEC since it's worried more about AC
electrical safety not RF grounding. In comm buildings R56 calls for using both
an underground ground ring/buss and bonded ground rods as a single system
bonded together.
However, your statement about rods closer than twice the length being
unproductive is true. It is a waste of money and has little effect on ground
resistance, but I doubt it does much harm if any overall. And the "two-times
length" maximum is also true.
I'd rather have any and all above ground, bonding connections from/to each
service (AC, cable TV, ham radio, telephone) as short of a run as possible to
the earth (e.g. buried, bonded ground rods) even if that meant the 8 ft rods
were only 6-8 ft apart. This would be required for an RF single point ground
system as I know it.
These are interesting NEC links for those with time on their hands:
http://www.necconnect.org/resource/?Id=1000027&Asset=c67370a9-8aa8-4606-a9c9-bb631a89c2e2
http://fyi.uwex.edu/mrec/files/2011/04/W4.-Biesterveld-NEC-grounding-MREC2010.pdf
73, de ed -K0iL
-----Original Message-----
From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of Rik van Riel
Sent: Saturday, January 17, 2015 11:09 AM
To: rfi@contesting.com
Subject: Re: [RFI] w7ekb & ground rods
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
On 01/15/2015 04:45 PM, EDWARDS, EDDIE J wrote:
> Excellent point Jim. All services' grounds (AC, telephone,
> television, internet and ham shack cable entry point & ham tower)
> must be bonded to a single-point ground system. There's no limit
> on number of ground rods as long as they're bonded (i.e. tied to
> the same grounding system). 8 foot ground rods need to be within
> 16 ft of each other, but can be closer if needed to shorten cable
> run to each service ground connection.
I thought NEC specified the opposite, specifically that
ground rods had to be at least twice their length apart,
in order for each rod to have its own independent
connection to ground.
In other words, ground rods spaced closer together than
twice their length will not result in as large a reduction
in ground resistance as ground rods spaced the recommended
distance.
- --
All rights reversed.
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