In reference to the use of aluminum alloy lugs to connect copper ground
wires to a tower:
I am wrestling with the same problem right now. Especially since I just
found out that you can't strap anything to the legs of a crankup. (The
inside sections slide against these legs). The aluminum alloy lug
recommendation seems to me, to be better that most I have heard so far.
I know most people recommend using stainless steel shims between copper
conductors and galvanized tower legs, probably because that is the way
Polyphaser makes their clamps, but I am still trying to figure out why
stainless steel is good to use in this application.
If I can remember any basic chemistry, the object here is to minimize
the galvanic potential difference between the metals that are exposed to
the electrolyte. Another goal is to maximize the area of of most anodic
metal exposed to the electrolyte (in this case the zinc tower), compared
to the area of the cathodic metal. In the case of attaching a clamp to a
tower, the area between the clamp and tower is the same for both
materials, since the water may penetrate this junction, but the whole
thing is not going to be emerged in water. This may not be true for the
copper to clamp connection, depending upon how the clamp is made. In the
galvanic series, zinc is around -.98 to -1.03, aluminum alloys are -.76
to -1.0, copper is -.3 to -.57, and stainless steel varies a lot
depending upon the alloy and may be -.46 to 0.0. So why is it better to
insert stainless steel between the copper and zinc? Seems to me a
better choice is to use aluminum alloy between the tower (zinc) and the
copper, assuming you are trying to protect the galvanized tower. The
clamp (or intermediate material) to copper connection is still at risk
for corrosion. Am I missing something here? Comments?
In any case, when you are making a transition between two metals widely
dissimilar, such as copper and zinc, no matter which intermediate
materials you use, there is potential for galvanic corrosion. It seems
to me that the only way to really eliminate the corrosion is to use a
good antioxidant on the joint and seal it against water. Oh, and also
avoid materials which corrode badly by themselves, such as raw steel.
I'm not sure which clamp you purchased, but I also purchased a standard
electrical clamp to test (Home Depot type). I don't think it was tin
plated, it seems to be raw aluminum alloy. It tests at only 30 mv
different from raw soft aluminum. Tin is closely matched to copper, but
not so close to zinc, so I think I would choose the aluminum alloy clamp.
Jerry
William Q Meeker wrote:
>There has been previous discussion on TT about how to connect copper wires
>to a galvanized tower (e.g., for lightening ground protection or when the
>tower is to be used as a radiator).
>
>My electrician has suggested to me what appears to be an especially simple
>and inexpensive solution for this need---the use of an aluminum alloy
>"mechanical lug" that bolts to whatever and has a screw-down clamp for the
>conductor. These lugs are available at any electric supply house and come
>in two sizes. The smaller one costs a little more than a dollar handles
>down to #6 wire. The larger one costs a little more than $2 and will handle
>down to #2 copper wire). The 1/4 inch hole is perfect for the smaller bolt
>on a Rhon-25 tower leg. The ones I found locally are manufactured by Ideal
>Industries. The package says clearly "for copper or aluminum conductors"
>and in a Google search I found the following description
>
>"The Power-Connect mechanical lug line includes lugs that are UL-listed for
>600VAC for wire ranges of 6 to 14AWG through 1000 to 500kcmil cable, and
>are acceptable for use to 2000V. Lugs are dual-rated for both aluminum and
>copper conductors and are electro-tin plated, made of high-strength
>aluminum alloy. Ideal Industries, Inc."
>
>
>The instructions say to use an antioxidant (presumably on the conductor
>before it is clamped).
>
>Does anyone see a potential problem using these lugs in tower-related
>applications?
>
>73,
>
>Bill
>K0KT
>
>
>
>
>
>
>William Q. Meeker
>Department of Statistics
>304C Snedecor Hall
>Iowa State University
>Ames, Iowa 50011
>Phone: 515-294-5336
>Fax: 515-294-4040
>Home Fax: 515-232-1323
>www.public.iastate.edu/~wqmeeker
>
>_______________________________________________
>
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
>questions and ask for Sherman, W2FLA.
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|