[TowerTalk] Aluminum radials

Fri Jul 14 18:40:23 EDT 2006

Yes the Al conductor has become the most common service entrance conductor and is the most problematic. The Al creeps out from under the setscrew connections and since you can't get at the ones in the meter base, these are the ones that seem to burn up the most often. The loose connection makes heat and the thermal cycling accelerates the creep till you get arcing. its all over at that point. If it's one of the phases you just get half the panel out. If it's the neutral then things burn out in house as the loads vary on the phases allowing voltage to soar on lightly loaded side. The type of cable you described is called SE cable and can't be used after the first bonding point of the neutral because a neutral past that point must be insulated conductor. This means the feed to your tower that uses USE or any underground approved conductor must have insulated neutral but the ground can be bare.

  The setscrews may be bound up if you used too much force when you installed them.
  Try to get close to manufactures spec's which are usually on the lug or a label near by. Use of torque wrench recommended for those not familiar with torquing set screws.
  The backing up of the setscrew 1/4 turn and then resetting is how we always do it to check for cross-threaded or bound up screws. 

  This topic started with aluminum radials and the only low priced Al wire I have seen is fence wire that is bare and about AWG #16. This holds up well above ground but can be problematic under ground. I would like to hear of any other Al wire  bigger that's cheaper

  Metal thieves steal all the copper and aluminum that's visible around here. Any store that closes for a week or more they steal all the refrigeration tubing and power wire. All guard rails around here had to be changed to steel on bridges or overpasses. I just know that one morning I'm going to get up and find the experimental antennas I have on the ground will be gone or the heliax cutoff. Sure don't leave the aluminum ladder out either. Thinking about tower guards to stop climbing too. (never needed them out here in country)

  Radial material might be purchased from scrapper at a few pennies over scrap cost which is lower for insulated than bare and the #10 and #12 lower that big solid wire.
  Tell them what you are looking for and what you are using it for and they will save the most suitable for you rather than shredding it to remove insulation.

  73
  Nick
  WB7PEK.

K8RI on Tower talk <k8ri-tower at charter.net> wrote:

> Aluminum has several characteristics that make it a bad choice for any 
> current carrying conductor.
> First is the fact that when placed in soil under even the smallest 
> current it wants to return to the state it was >as a ore. Hence you get a 
> nice white powder/scale like the bauxite it was refined from.
> Second you always have a problem with migration out from under any 
> setscrew connection.(That's why its >not a common housewireing practice 
> after the fiasco in the early 70's and all the fires traces to connections 
> >that loosen up after a year) Thermal cycling with the large coefficient 
> of expansion and its natural softness of >wiring

I think you will find that it has again become common practice to use 
Aluminum at least from the meter to the breaker panel. I couldn't even find 
00 Sopper and had to settle for 0000 Aluminum. The feed for the house 
reminded me of the old #6 feed for mobile homes except it was 0000. 2 
conductor plus ground with an overall wrap with insulation. The outside of 
the stranded conductors appear to be swedged smooth so they appear as if 
they are a solid conductor until you take a closer look.

The feeds in the shop from the meter to the panel are individual 0000 
Aluminum that also have the smooth outter appearance. The go into the meter 
and panel with lots of antigalvanic compound and those connectors (allen set 
screws) are torqued down really tight. After they were as tight as we could 
get them by hand we used an Engineers 5# hammer on the over size allen 
wrench to finish tightening them. IMO 0000 Aluminum is terrible to work 
with compared to 00 Copper. We had to use pipe benders to prebend most of 
the cables as far as we could and still get them through to the connectors 
at the other end.

>grade Al explains all. When used in electrical services they either use a 
>special crimped lug of if setscrew it >must be re-tightened on a yearly 
>biases. The lack of yearly checks on Al wire is the most common service 
> >failure.

They have to be checked on a yearly basis, but after five years we've not 
found one yet where the wrench would even move. OTOH I sure wouldn't want 
to use the stuff for the wiring after the breaker box. In addition to the 
other problems the wire has to be twice the physical size of copper and I 
doubt you'd find many outlets that would even take that size wire. I don't 
belive "wire nuts" for splicing, or junction boxes would be acceptable 
either.

> Third is that Al will form aluminum oxide in minutes on freshly bared Al. 
> This is the black stuff you get on your hands putting your antennas 
> together. It is a very poor conductor and is more of a problem with 
> plumbers delight type of construction as compared with antennae that use 
> insulated from the boom elements.
>
> Aluminum is a wonderful metal, they just haven't yet figured out how to 
> make it hard and corrosion resistant

There are indeed some very hard alloys of Aluminum, but unfortunately you 
either settle for hard OR good corosion resistance. Like a high performance 
airplane that can come down or slow down you can't do/have both. Aircraft 
use alloys that are quite hard, but they are alodyned before paining. 
Alodyne works very well, but it is thin and fragile. It's not all that 
difficult to do, but it does take time and can be messy. As the first step 
is a Phosphoric Acid etch I'd not want to do it on stranded Al. The process 
it basically treat and wash, treat and wash, treat and was and this is after 
the etch. When you finish the Al should be a nice Gold color that looks 
almost transparent.

> and still high conductivity. The smelter that produced the purest Al for 
> wire was shut down due to a buyout >by competitor wire manufacturer from 
> overseas. Go figure?

Unfortunately, although pure Al is the most corosion resistant it is soft 
and has, I believe, the highest coefficient of expansion making it poor for 
connections.

Both Anodizing and Alodyining do a good job of corosion proofing, but both 
are fragile.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com
>
> Nick
> WB7PEK
>
>
>
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