Copper strap

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K8MHZ

K8MHZ

Senior Member
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Michigan. It's a beautiful peninsula, I've looked
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Electrician
I need to repair a broken grounding electrode connection for a radio tower. What I am up against is 6 inch wide copper strap used as a grounding electrode conductor that needs to be attached to a 5/8 inch grounding electrode. The original installer used solder to attach the strap to a bare stranded copper wire and then Cad welded the wire to the electrode. He left it exposed and it got ran over by a vehicle and the connection broke. The inspector pointed out that the solder only connection was an NEC violation. I also pointed out that the connection was left unprotected. I need to make this repair soon and since it will be inspected it has to be code compliant.

The inspector suggested using ground clamps for a mechanical connection with solder as an addition. I would rather use something listed for this type of connection as clamps do not appear to be listed for use with strap. The inspector is being very lax and his main concern is safety and functionality. My requirements for this job have exceeded his expectations. Our company did not do the original installation. The company that did never pulled an electrical permit and I was called in to work with the inspector and pull and close out a legal permit after the fact, so to speak.

What is being protected is a 200 foot tall rotating amateur radio tower. If I did the design I would have used a different method, but it's too late for that.

Any help would be appreciated. I did put in a call to Theka (they design and install cell towers) and am waiting for a call back. The owner lives near me but is a pretty busy guy so I don't know when he will call me back.

Thanks
 
Why not buy 2 clamps,one for the rod and other on 1 of the steel legs of tower.Would suggest min of #4 but might be smart to go larger.What is the inspector trying to do here ? Ground rod will not clear any faults,just static and lightning.The motors need grounded to electrical source.
 
Now I just said in another post not to over think the question, but my thought is that it doesn't seem so much that the grounding method was wrong as that it was hit by a vehicle. I would think about installing the rod in a well.

I'm trying to picture what you have in my mind. Can you attach some kind of lug to the strap and then just run a ground wire over to the ground rod? Or is this strap more like you would see on ESD mat where it just wraps around the ground rod?
 
Jim W in Tampa said:
Why not buy 2 clamps,one for the rod and other on 1 of the steel legs of tower.Would suggest min of #4 but might be smart to go larger.What is the inspector trying to do here ? Ground rod will not clear any faults,just static and lightning.The motors need grounded to electrical source.
Click to expand...

Hello Jim,

The tower has no legs. It is a 'UniPole', a huge steel pole with a sprocket at the base. The entire tower rotates to position the large array of antennas on it. The strap is used to connect the grounding window, a copper plate in the wall where the coaxial antenna feed lines pass into the control building, to the ground field which encircles the tower and building base. The tower is 500 feet or so from the transmitter room. The copper plate is used as a low impedance ground for the surge arrestors protecting the equipment from lightning strikes. The arresters are 'Polyphasers' with replaceable cartridges that will fault to ground in a surge situation. In order to work properly they must have a very low impedance to ground connection, thus the wide copper strap and the ground field. The lightning protection is to not only keep the operator and his structure safe, but also to mitigate any damage to his station which has many thousands of dollars worth of equipment in it.

w8ss.1160010569.jpg


Believe it or not, this is a hobby station. It may very well be the best built privately owned amateur radio station in the country. It is over 150 miles from me and the owner trusts no one but me to work on it due to getting burnt by the previous contractor. I want to be able to provide him with the best of the best as not to compromise his trust in me. Not only that, my standards are pretty high and I do not like cobble jobs.

Sorry I don't have any pics of the tower right now. I shot them in film and haven't got the film developed yet. (I know, I know, film is so old school but I have a very nice Canon Elan and a bunch of film left over so I took it out to the site when I went last time)
 
cowboyjwc said:
Now I just said in another post not to over think the question, but my thought is that it doesn't seem so much that the grounding method was wrong as that it was hit by a vehicle. I would think about installing the rod in a well.

I'm trying to picture what you have in my mind. Can you attach some kind of lug to the strap and then just run a ground wire over to the ground rod? Or is this strap more like you would see on ESD mat where it just wraps around the ground rod?
Click to expand...

Hi John,

Well, I don't know what type of lug would be listed for use on a 6 inch wide copper strap. I have never seen ESD mat as you mention but I could envision wrapping the strap around the rod. My question would be how to make the mechanical attachment in a code compliant manner. The NEC does not allow solder to be used as a sole means of connection.
 
http://www.polyphaser.com/productdetail.aspx?item=58R-112S

This is described as a clamp for attaching copper strap directly to a 5/8" ground rod. It is specified for 1.5" strap, but the description says that it may be used on up to 6" strap.

Given the wide surface area for contact, I presume that the pressure is low and the connection not gas tight. I wonder if some sort of termination compound is in order, but have no idea if this is necessary.

-Jon
 
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Solder is a problem but you could braze them together. Cadweld (Erico) has a large variety of mold combinations, you may be able to cadweld right to the tower itself .
 
K8MHZ said:
Hi John,

Well, I don't know what type of lug would be listed for use on a 6 inch wide copper strap. I have never seen ESD mat as you mention but I could envision wrapping the strap around the rod. My question would be how to make the mechanical attachment in a code compliant manner. The NEC does not allow solder to be used as a sole means of connection.
Click to expand...

Electro static discharge mat. You use a special adhesive on the floor and lay this thin copper strip in it, it's almost like a copper foil then you run it over to the ground rod and simply wrap it around it using an adhesive.

If the copper strap you have is like what we you would use to connect all your grounds together in a room like we see on cell sites or when you're running your grounds from floor to floor in a high rise, I would think that any copper lug would be fine.

Is an inspector involved because it's privately owned? Ususally we don't care about the grounding of the mono poles here, and they are grounded to all get out, as it's usually the providers requirements and not ours.

Again. with out seeing it I'm just guessing as to what you have. Sorry.
 
You could also fold over each corner of the strap, making a point that is three layers thick, and drill a hole and use a nut and bolt to attach a mechanical lug.

I don't know it it's compliant, but it would work.
 
Too little too late they make them for connection to wire as well


Ground Wire to Ground Strap Clamp

Corrosion free clamps provide a good connection of ground wire to copper strap without having to build up the joint for an exothermic weld. All copper sandwich with 18-8 stainless hardware. Large contact surface smashes the strap into place. Less than .0001 ohm resistance. Can be used for 0.5" to 3.0" copper strap. Joint compound not included.
Item#
Qty/Uom Manufacturer
Mfg. P/N
Warranty Description

Wt. (lbs)
Wgt. (kg.) Price
Log in Now
33089
1 EACH PolyPhaser
1C-112S
10 Years #6 to #1 AWG Ground wire to 1.5", 3" or 6" copper strap

0.60
0.27 List$33.00


59353
1 EACH PolyPhaser
10C-112S
10 Years 1/0 to 6/0 AWG Ground wire to 1.5', 3" or 6" copper strap
 
two cents

two cents

A strap cross-section has less inductance per foot than other shapes, so I'd maintain that cross-section whenever you can.
 
zbang said:
I wouldn't do that, the heat will change the mechanical characteristics of the tower metal and very likely weaken it. Falling towers are Not Fun.
Click to expand...

Agreed and also not possible. This tower is a metal pole that rotates. I would do nothing to a tower that has any chance of compromising the metallurgical properties of the tower.

I have to thank the additional posters for their suggestions of strap connections from PolyPhaser. PolyPhaser is the best source for surge protection devices and I feel remiss for not checking them out initially.

I have to admit, this forum is a *very* valuable asset to progressive and quality minded electricians. I can't say enough good about it.

Thanks again!
 
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