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Author Topic: Not all "copper" wire is copper  (Read 3942 times)
K0IZ
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« on: February 23, 2014, 03:44:51 PM »

I was shopping for some 18ga/2cond wire, and found several sources for 500ft at good price.  Should others be shopping for copper cable, be aware that some is now copper plated over aluminum.  Appears to be copper in photos, even stranded type.  But NOT solid copper.  The real stuff costs somewhat more, of course.  And worth it.
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KE4JOY
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« Reply #1 on: February 23, 2014, 04:07:15 PM »

Cu Clad has been around for a long time and is usually marked as such on its insulation as CCA or CCAW

I don't really get all the adversion to the use of aluminum conductors. The industry has come a long way in reducing the stability issues of the past. The biggest pitfall is the installation practices and the lack of using allox grease and over torqueing the connections.

In the past there was stability issues with aluminum conductors where the conductors would actually swell when hit with an inrush and would eventually work loose at their connection points. As I said reputable producers have made great strides in the mettalurgy to reduce this tendency.

http://en.wikipedia.org/wiki/Staballoy

Now when you get into velocity factors and Cu vs AL that argument is wide open. But my opinion is that due to skin effect and rf frequencys you should see little to no difference between solid Cu and CCA/CCW
« Last Edit: February 23, 2014, 04:09:48 PM by KE4JOY » Logged
K0IZ
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« Reply #2 on: February 23, 2014, 04:43:26 PM »

My use was not RF, but alarm sirens and other similar stuff.   So skin effect not relevant.  And I was using 18ga for lower voltage drop on some long runs vs lesser gauges.  Copper/aluminum not equal to copper.  The suppliers did not specify and photos of apparently copper stranded wire would lead one to expect copper.  Not so. 
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G3RZP
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« Reply #3 on: February 24, 2014, 03:31:03 AM »

One skin depth in copper at 1.8MHz is 0.002 inch. Usual 'rule of thumb' is that you should have 5 skin depths for the current to be below about 0.7% of the surface current - so you need about a .010 thick cladding for use at 1.8MHz. Admittedly, the aluminium isn't that bad a conductor on its own, but don't discount skin effect.
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K9MHZ
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« Reply #4 on: February 24, 2014, 05:46:57 AM »

Is there a strength and/or stretching issue to consider as well, especially for long antennas lengths?  Makes you wonder is a stronger alloy inside the wire might actually be a good thing (?)

Dunno.



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KE4JOY
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« Reply #5 on: February 24, 2014, 01:38:44 PM »

There used to be copper clad steel wire available to deal with 'stretching' it was specifically made for longwire antennas. Don't know if it is around or not.

Strangely enough NEC 310.16 does not even list an ampacity for 18ga cu clad!

http://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

But if your applications were current limited as I suspect they are it probably would not be an issue as voltage drop is directly correlated with current drawn.

Still the seller should have clearly stated that it was indeed cu clad wire but I am guessing they were probably un aware of it.

I did not even know you could get stranded 18ga in cu clad. Learn something every day!
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KE7TMA
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« Reply #6 on: February 24, 2014, 04:21:20 PM »

I don't really get all the adversion to the use of aluminum conductors.

Two words: galvanic corrosion.
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KE4JOY
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« Reply #7 on: February 26, 2014, 12:43:21 PM »

Almost all devices these days from breakers to receptacles are rated cu/al. That and the proper use of noallox along with improved materials galvanic corrosion is not the issue it once was.

Now if you put aluminum under cu only lugs with no grease yea your going to have an issue. Also exposed to the weather conditions as often seen in long wire antennas and such may also be an issue.

There is no question that pure Cu conductors are superior to Aluminum or even Cu clad. But I personally feel the aversion to aluminum is really carried over from 'the good ole days".

ps; I personally have seen the results of a plasma fire which raced up a vertical aluminum busway that was started by improper techniques at the terminations (improper torque and no grease) and al under cu only lugs. That was a sight to behold!
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AA4PB
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« Reply #8 on: February 26, 2014, 01:00:39 PM »

You should take a look at your home's electrical panel. In a modern home you'll most likely find that the kitchen stove circuit and the service drop from the power company uses aluminum wire.
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KE7TMA
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« Reply #9 on: March 12, 2014, 11:17:50 PM »

You should take a look at your home's electrical panel. In a modern home you'll most likely find that the kitchen stove circuit and the service drop from the power company uses aluminum wire.


You'll also find radioactive drywall and granite countertops from China, pressboard floors and ceilings, and carpeting that emits foul vapors which are known to cause health problems for several years while they outgas.  Aluminum wiring is simply a cheap way to get juice flowing, by sacrificing long-term reliability.  Galvanic corrosion is a heck of a beast.
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AA4PB
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« Reply #10 on: March 13, 2014, 07:18:41 AM »

The aluminum service drop and range wiring in my house have been there since 1980 without a failure. Certainly these large conductors are aluminum in lieu of copper to save money, but it doesn't sacrifice reliability if its installed correctly with the proper terminations.

The big aluminum wiring issue of years ago (I've done repairs on a number of such houses) came about because it was smaller branch circuit wiring (usually #14 for 15A service) that was connected to copper terminations with no antioxidant. Using aluminum wiring for the larger conductors today is not an issue.
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KD0REQ
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« Reply #11 on: March 13, 2014, 07:27:51 AM »

lesser conductivity means you have to upsize aluminum wire one standard gauge for the expected current capacity.

aluminum also expands and contracts more in service, which means you have to crank 'er tight and be vigilant.

for all these reasons, it is not recommended to use aluminum except for single-connection dedicated purposes inside a home.  when I was working as a hospital maintenance assistant to get through college the second time, we had Al conductors of proper size and properly treated jumping out of boiler distribution pumps in the power plant.  a great pyssedness arose, and it was all changed out to copper.  no further issues.

you don't see those issues in overhead feeds because of the monster crimp connectors used.  in the case of 300,000 volt range overhead lines, there is a steel core in the cables for strength, and they use explosive connectors that fuse splices with heat and extreme pressure.
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