FW: [TowerTalk] Unique RFI/Grounding system

[Steven Gehring]

Steven J. Gehring
19713 26th Drive SE
Bothell, WA  98012-7252
Mobile: 206-849-1218
E-mail: stevenkz9g at speakeasy.net
 


-----Original Message-----
From: Steven Gehring [mailto:stevekz9g at speakeasy.net] 
Sent: Monday, June 02, 2003 4:45 PM
To: 'Jim Lux'
Subject: RE: [TowerTalk] Unique RFI/Grounding system


Hi Jim,

I wasn't aware that my home's building ground was a specially designed,
rebar welded ground spread throughout a building foundation.  I thought it
was a just a ground rod here in WA (my house is 25 years old).  Check out
these links:

http://www.psihq.com/iread/ufergrnd.htm

http://lists.contesting.com/_towertalk/1997-September/009267.html

http://www.spgs-ground.com/typesA.html#anchor1772206

Maybe in California the UFER ground is more standard. Reference:

Ufer Ground

INTRODUCTION

As stated in Article 250 - Fine Print Note No. 1 of the 2001 California
Electrical Code (CEC), “Systems and circuit conductors are grounded to limit
voltages due to lighting, line surges, or unintentional contact with higher
voltage lines, and to stabilize the voltage to ground during normal
operation. Equipment grounding conductors are bonded to the system grounded
conductor (neutral) to provide a low impedance path for fault current that
will facilitate the operation of over current devices under ground-fault
conditions.”

The Grounding Electrode System is installed to provide surge protection and
voltage to ground stabilization. This system is required at each building or
structure on the premises. There are numerous methods described in the code.
The most common is the Concrete Encased Electrode or UFER and the Driven Rod
Electrode. The CEC allows the use of metal underground water pipe. This
method requires a supplemental electrode be provided. This requirement is
based on the practice of using plastic pipe for replacement when the
original water pipe fails.


TECHNICAL DETAILS

When available the building reinforcing steel (rebar) is the preferred
method for providing an electrode. Concrete Encased Electrodes (UFER) can
consist of either a minimum of 20' of No. 4 copper wire or two or more No. 4
or larger rebar installed in the foundation with a minimum of 2" of concrete
cover. When using rebar, it must be spliced a minimum of 40 bar diameters,
ex. 40bd x 1/2"=20" min splice length. 

When a UFER ground is installed in a pier and grade beam foundation system a
number of methods are available:

Use the rebar in the pier if 20' deep or more. 
Install 20' of No. 4 copper in the pier if less than 20' deep.

Bond two or more pier rebars together with either copper or rebar connectors
if less than 20' deep. 
Grade beams intended to retain a minimum earth contact of 2" or more can be
treated as a standard T foundation system and ground accordingly. Grade
beams without a minimum 2" of earth contact should follow items i., ii, or
iii above.
 
A Driven Rod Electrode must be installed so that at least 8' of its length
is in contact with the soil. It can be driven at an oblique angle not
greater than 45 degrees from the vertical or buried in a trench at least 30"
deep. The most common type is a listed ½" copper rod. 

The grounding electrode is connected to the system with a Grounding
Electrode Conductor. This must be run unbroken to the bonding bus bar at the
service disconnect enclosure. It may only be spliced with a listed
connector. It must be protected from physical damage and securely fastened
in place. When ground clamps are used for terminations they must be listed
for the type of materials used and approved for direct burial.




REFERENCES
2001 California Electrical Code Article 250-81 through 86 Sonoma County
Residential Construction Handbook Section 17.7 


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E 250-81 through 86

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Effective: 9/01/01
Revised: 12/31/01

Steven J. Gehring
19713 26th Drive SE
Bothell, WA  98012-7252
Mobile: 206-849-1218
E-mail: stevenkz9g at speakeasy.net
 


-----Original Message-----
From: Jim Lux [mailto:jimlux at earthlink.net] 
Sent: Monday, June 02, 2003 4:17 PM
To: Steven Gehring; 'Mark Pride'; towertalk at contesting.com
Subject: RE: [TowerTalk] Unique RFI/Grounding system


At 03:44 PM 6/2/2003 -0700, Steven Gehring wrote:
>Hi Mark,
>
>Do a search on the internet (Google) for what is called a UFER Ground.
>There are many hits on this type of cement foundation grounding method.  
>I hope this helps...
>
>Besides following the NEC, I'd like to employ this method the next time
>I build a new house.  I suppose this UFER ground could be bonded to the 
>building ground and a single point ground panel.


The UFER ground IS the building ground. You wouldn't generally see a 
conventional ground stake tied to a UFER ground (if only because the UFER 
is a better ground.. lots of contact area, low impedance, etc.)

One could use a UFER ground at the tower and at the shack, and tie them 
together per the NEC...

Jim, W6RMK