Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Grounding Rods (Galvenized or Copper)  (Read 2859 times)
KD7ZVL
Member

Posts: 123




Ignore
« on: April 16, 2004, 02:03:27 AM »

Hello,

I am going to be putting some 8 foot grounding rods into the earth, and I am wondering if I should go with galvenized, or copper rods?  The other day I bought a couple of galvenized ones, but a couple of local hams told me I would be better off with copper ones because of better conductivity.

Should I be concderned with what I have already purchased or not?

73

Bill
Logged
K0ZN
Member

Posts: 1547




Ignore
« Reply #1 on: April 16, 2004, 02:37:33 AM »

Hi, Bill.

Interestingly, a few weeks ago there was a good deal of discussion on this topic, but it was related to dissimiliar metal corrosion between copper and galvanized ground rods. There were some knowledgeable comments on the subject. The bottomline is this: in terms of GROUNDING, the galvanized will work as well as the copper. There is very slightly more DC resistance in the galvanized coating than a copper coating, but it is insignificant to real world applications, especially for static electricity and lightning protection grounding. Your radio will NEVER know the difference between the two types of plating. You can put an ohm meter on the two and see for your self if you are curious. Keep in mind the ENTIRE surface of the ground rod is the contact area, which is a big "patch" for contact, which further reduces the difference between copper and galvanized.

HOWEVER !!!! There IS a real and serious problem with corrosion between a copper and galvanizing (which is Zinc, essentially). You CANNOT connect a copper ground cable directly to the galvanized rod or it it WILL corrode and you WILL end up with a high resistance connection. The solution to this is to get a piece of thin stainless steel "sheet stock" at a hardware store, and roll it into a "scroll" and place it over the galvanized rod and then connect your bronze ground clamp and copper cable to the STAINLESS STEEL. This is not an ideal situation, but it is quite "adequate", especially for static and lightning protection.

I had been using copper rods, but happened to pick up some galvanized rods on sale the other day, I knew of the corrosion problem between the two metals, but just didn't think about it... so I had to go through this exact thing about two weeks ago!

The difference between copper and galvanized ground rods is kind of a "hell if you do, and hell if you don't" deal. The copper is a fracionally better conductor and a copper cable can be connected directly to it, BUT... the copper coating doesn't protect the steel in the rod all that well, and EVENTUALLY, a copper coated rod WILL rust way to nothing. Some soils are pretty bad about this. Galvanizing on the other hand has some "sacrificial" properties and really does offer some protection to the steel rod, allowing it to last longer. NO ground rod will last "forever", and in a long term situation, they should be checked after a few years.

Knowing what I know now, I probably would not buy galvanized rods again, but I would (and did) use the ones I had.

There is one other alternative: If you have relatively soft and rock free soil, you can sink a length of pure copper water pipe by making a hose adapter for it, forcing water through the pipe and "water drilling" it into the ground. Kind of messy, and slow, but it does work. The pure copper pipe (typically 1/2" water pipe) will last "forever" compared to a steel rod. I have done this and it works very well.

FYI: The U.S.Army Signal Corp did some research a number of years ago, and came to the conclusion that ground rods connected in series were slighly more effective than rods connected in parallel. Since you (wisely) were going to install two rods, I thought I'd pass this tid bit along...

Many hams "cut corners" on their station ground system and it is a bad mistake. A really good, low resistance earth ground is WELL worth the effort.

73 and good luck.     --  K0ZN
Logged
K9KJM
Member

Posts: 2415




Ignore
« Reply #2 on: April 16, 2004, 07:01:49 AM »

Good answers from K0ZN. For lots of good information on lightning protection grounding, See the tech notes on the Polyphaser website:
http://www.polyphaser.com/ppc_pen_home.asp
As a general rule, Ground rods should be space about twice the distance apart as the depth (8' deep rods spaced 16' apart)
Two rods is a start......    Depending on local conditions, Lots more may be needed for a real lightning ground.......  
Logged
AC5E
Member

Posts: 3585




Ignore
« Reply #3 on: April 16, 2004, 08:35:24 AM »

Good answers - one slight correction.

The stuff you want between copper and anything galvanized is stainless steel "SHIM" stock - usually available at the professional auto parts stores such as NAPA and at most industrial supply stores. I use the .002 stuff myself and usually take two wraps.

If you have a choice your local NAPA store is usually cheapest.

73  Pete Allen  AC5E
Logged
N7NBB
Member

Posts: 380


WWW

Ignore
« Reply #4 on: April 16, 2004, 10:53:39 AM »

Be sure to SPACE THE GROUNDRODS AT LEAST 16 to 18 FEET APART (NEC)
any closer and you are esentially building a CAPACITOR in the earth.

Also it is now the current vougue (no pun intended) and also part of the NEC, to use FLAT STRAP rather than braided cable or large guage wire when connecting (grounding) equipment and subsequent "earthing".

73
CAM
Logged
K0IZ
Member

Posts: 737




Ignore
« Reply #5 on: April 16, 2004, 12:56:15 PM »

Some of the big box stores (Home Depot, Lowe's) are selling the 5/8 x 8ft copper plated rods for well over $10 each (Home Depot in Kansas City area has for $13+).  However the local wholesale electrical distributor (selling to contractors, etc) sells same for just over $7.  Also better quality bronze clamps.  

I would recommend copper plated to avoid the electrolysis problem, and checking out a cheaper source.  Also 10ft is better than 8ft.
Logged
N6AJR
Member

Posts: 9906




Ignore
« Reply #6 on: April 16, 2004, 05:54:15 PM »

I got some 8 foot rods from home depot and they worked fine.  go back in the chain link fence section and buy your self on of those fence post drivers  for about $16  or so.

 they are like a heavy tube  a couple inches in diameter with the top welded shut and a couple of handles on the side ( painted purple)  you slide them over the end of a fence post and slam it into the ground.  

it works great on ground rods, I did 2 in a matter of a couple of minutes.  I also use it to drive in short sections of pipe to mount my push up masts into.    question though. I wonder if a ground rod would work just as well burried in a trench 8 feet long and down about 2 feet, instead of straight up and down  Huh
Logged
K0ZN
Member

Posts: 1547




Ignore
« Reply #7 on: April 17, 2004, 01:14:53 AM »

Hi, Two quick comments.

I did look for "shim" stock, per Pete's (I think it was you, Pete) who in the earlier discussion on ground rods, recommended the stainless steel. None of our local autoparts stores had it, but I was able find a "sheet" (it was about 6" X 8") of stainless steel at a hardware store that was "very thin" and worked well to wrap around the ground rod in a couple of layers. It was in the section with brass stock and small tubing, etc. Bottomline is there are sources of this stuff.

As far as burying a rod in a trench... the main intend of the rod is to penetrate deep enough to get into moist soil. I many areas of the country (like mine!) in the summer the top few feet of soil can get bone dry and have little conductivity. If you want to dig a DEEP trench, yes, you can bury a plate or long, large diameter piece of copper pipe, etc. More surface area is better... if it is in soil with good conductivity, which is mainly good moisture.

73,    K0ZN
Logged
N5EG
Member

Posts: 246


WWW

Ignore
« Reply #8 on: April 17, 2004, 12:06:39 PM »

Most hardware stores sell clamps for connecting a ground wire to the grounding rod, and they're very inexpensive. They are also probably compliant with the code.

  -- Tom, N5EG
Logged
KB9CRY
Member

Posts: 4283


WWW

Ignore
« Reply #9 on: April 19, 2004, 11:16:53 AM »

If you go with clamps, make sure you purchase the ones with all brass parts, including the screws.  Cheaper units have steel screws which will quickly rust and corrode.  A problem though with clamps is that you must constantly retighten them.  The thermal cycling of the outdoor temps will cause them to loosen; figure you'll have to do this at least twice per year.  And, if they're buried, you'll quickly loose your connection.  The best way to go is an exothermic welding connection, CadWeld or Uniweld.  Go to erico.com to spec out CadWeld units, then go to an industrial supply house to order the units or go to the Hargar website (do a Google search) to purchase the Uniweld units.  Totally weatherproof and maintenance free.  For the cost, they are very much worth it.  Phil  KB9CRY
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!