Bonding earth rods together

[VK5ZEA]

Hi Everybody,

I'm looking at ways to bond three earth rods together. The three are in a row, at 50cm spacing.
The rods are 1.6m long and are copper clad steel.

I've tried soldering 50mm wide copper strap to the rod, cleaning the copper with emery paper and prepping with flux, wrapping the strap around the rod and heating with a gas torch... but the solder just flows out of the joint and doesn't fill the gaps between the rod and strap. (damn gravity!).

I have seen installations where 1/4" thick strap is bonded to an earth rod with a thermite style welding reaction. I don't think my strap would survive a procedure like this.

I can't even think of a solution that would allow me to successfully solder the strap to the rods... so I am open to suggestions.

73

Michael.
VK5ZEA

 

[acyddrop]

My grounds are bolted in place with vice like jaws. I'm using (I believe) 2" (5cm) wide flat copper strap. There are 8, 8ft (might be 6ft?) rods they all tie back to a large solid copper bar which is then brought inside. But everything is bolted and not soldered. Bolts at the tower side as well.

Sent from my Funky EclipticRez v9

 

[BirkenVogt]

Try adjusting your soldering techinque. When soldering large objects that retain a lot of heat, you have to remove the torch and continue to feed solder as it cools and thickens. Also, try taking a full turn around the rod with the strap and then soldering the whole mess together.

You could also look for a bronze electrical grounding clamp with a large enough hole for the wire that you could make the strap round for a couple of inches and shove it in there.

The thermite device to which you refer is called "Cadweld" and is available at electrical supply houses. It is made for welding copper to ground rods and the like and I don't think it will hurt anything. It is the best way to go about it in this application, IMO.

You can also braze the rod and strap with brass filler instead of solder, which I have also seen done to copper wire and it makes a stronger bond than soft solder that can be direct buried without worry.

Finally, remember that any earth system that you make needs to be electrically bonded with a #8 copper wire or better back to your electrical ground system, either at the panel or to the ground rod or cold water pipe near the bonding clamp, to avoid any damaging currents from flowing through your radio and over your feedline in the event of a lightning strike or ground loss event of the power company.

 

[LtDoc]

Soldering is not a good way to connect things which may be hit by lightning, it tends to get 'flashed' away very quickly. A mechanical connection or 'cadwelding' is much more secure and can survive more than one strike.
- 'Doc

 

[prcguy]

I have used small stainless steel hose clamps to make large surface area connections of copper strap and braid to ground rods. You can use 3 or 4 spanning several inches to get a lot of contact area and the hose clamps will squish the strap or braid to conform to the shape of the rod.

50cm spacing between rods is unusual and there is a formula for spacing depending on the qty of rods and what your trying to ground. Going from memory about 2m is the closest spacing I have read.

The building I work in has probably 150 or more ground rods by now, mostly 10ft long with Cadweld for connections and the tops of the rods are about 4ft underground.
prcguy

 

[Rt169Radio]

Like one of the posters said, a soldered ground connection might melt during a lighting strike so its not the best to use.

 

[WA0CBW]

Not sure if this applies to your part of the world but in the US the National Electrical Code specifies either a mechanical or exothermic connections for ground rods (soldering is prohibited). If above ground the connections can be mechanical using an approved electrical clamp. If underground they must be "welded" using an exothermic method as mentioned above. If your copper strap wouldn't survive welding then it won't survive a lightning event. Ground rods should probably be a minimum of 4-foot to do any good (NEC recommends a minimum of 8-feet). They have an influence that is equal to their length. So a 4 foot ground rod has an influence of 4 feet in diameter. That means they should not be farther than 8 feet apart. Putting them closer than 8 foot does not improve their efficiency.
BB

 

[SkyPager]

While everyone says "Cadweld" remember that is a trade name for a paricular product. The proper name for the technique is "exothermic welding" You may also use the proper compression clamp provided you use the proper tool which will give 12 tons of compression.

Ground rods should spaced approximately equal to twice the length of the rod

Only proper clamps for bonding of dissimilar metals should be used.

http://www.bicsi.org/pdf/presentations/fall_2010/Grounding and Bonding Testing.pdf