What is the key technology for connecting aluminum?

wrote:


That is why CO/ALr devices us a screw that tracks aluminum's expansion rate.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

The biggest change in the "new" wire is it is harder but the expansion rate is virtually the same
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

So one thought is why don't they make a device where the screw terminals are backed by some form of spring, like Belleville washers. A properly sized spring would just allow the Al to expand/contract but maintain a suitable compression for good contact.
Such 'lock washers' and 'precompression washers' have been around for years in mechanical fasteners, can't imagine why it wouldn't work with simple wire terminal screws.
Of course this doesn't address oxide or wire-nuts, but it seems like it would fix problems with screw-terminals.
I know the stab-holes on the back of many devices are *not* listed for use with Al, but it seems a properly designed, spring-loaded contact for Al wouldn't be impossible. The sliding action when inserting could scrape off the oxide and a paste would ensure further oxidation is prevented.
Again, I don't know of any such equipment on the market, but it seems perfectly possible to build such devices. Maybe when copper prices get too expensive, we'll all be relearning Al wiring again :-)
daestrom
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
bud-- wrote:

You make a good point. I wasn't addressing screw terminal connections, so it is different, but it needed to be said.
Ed
<snip>
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Exposed Al oxidizes almost instantaneously. Does the paste remove the oxide thereby making a metal to metal contact possible? Why don't copper oxides (CuO and Cu2O) pose the same problem as Al2O3 does?

Bill
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Cupric oxides have good conductivity. I understand there is one oxide that has poor conductivity, but it only forms in very high heat, like fire.
j

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Salmon Egg wrote:

Pastes do not remove oxide. Pastes prevent further oxidation. Some pastes have?had metal particles that allegedly contact through the oxide. Some manufacturers, like Ilsco, want you to wire brush wire to remove oxides (large wire, not 15/20A stuff). As posted before, the recommended procedure for 15/20A wire, based on research, is to apply paste, abrade the wire, and use paste in the connection. See: http://www.inspect-ny.com/aluminum/alreduce.pdf

--
bud--

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
| snipped-for-privacy@ipal.net wrote: |> On Sun, 13 Apr 2008 14:54:40 -0400 Michael A. Terrell
|> |
|> |>
|> |> | |> |> | #14 Al wire has never been allowed for US branch circuits. |> |> |> |> But I was referring to an idiot's choice of wire. Likely he'll find that #14 |> |> Al is nearly impossible to find. And that would be sad because we'll lose the |> |> chance to remove that idiot gene from the pool. |> | |> | |> | Not if it's someone elses's home, or it lasts long enough to sell it. |> |> If you hire an idiot as an electrician, you get what you deserve. This is |> what inspectors are for (among other things). |> |> If you buy a home from an idiot (and don't inspect it to discover this error), |> you get what you deserve. |> | | A bit unrealistic. | | Most people who hire an electrician don't know enough to | determine that he/she is incompetant. | | A normal pre-sale inspection will not include disassembly | of the electrical system to determine wire size.
An electrician so dumb as to install wrong size aluminum wire is likely to be rather obvious in many aspects. Sure, some people are still too dumb to be able to recognize this. Back to my original statement.
The inspection of the work done by the electrician should determine wire size. If the work is of the type that requires new wire be installed, then it is likely to require inspection. Of course it depends on the local AHJ, and whether it is trying to avoid idiot electricians.
You can get good or bad pre-sales inspection services. Insurance requires a certain minimum. If you get what they require, and the house still burns down as a result, maybe you have a case against the insurance company. You might against the inspection service depending on the level of service contracted.
--
|WARNING: Due to extreme spam, I no longer see any articles originating from |
| Google Groups. If you want your postings to be seen by more readers |
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@isp.com says...

I thought the issue was #14-only back-stabs (on Cu, even). Personally, I'd rather they get rid of back-stabs entirely. Clamps, OTOH...
--
Keith

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 10 Apr 2008 20:10:45 -0700, Salmon Egg

Virtually all of the "aluminum" problems were workmanship related. There was a problem with the binder screw devices and the expansion rate of the screw metal vs the wire. That was fixed with the CO/ALr device which uses a screw wityh a bigger head and an alloy that matches the wire expansion rate. When aluminum wire is used in an aluminum lug all of this is eliminated and it will actually perform better than copper. Most lugs are aluminum. That is why it hasn't been a problem in larger wire sizes. The Noalox is mostly a fewel good prodfuct and it is not required in the listing of any lug I know of but it is "recomended" by some. There are currently 3 principle devices on the market for splicing aluminum or aluminum to copper. You have the high end "Copalum" one time crimp system that requires a certified installer, special tools and is very expensive. There is the Ideal 65 purple wirenut that is /L listed but has a bad rep in a 30 year old CPSC article, still widely circulated. It is suspicious because it lools like it was really written by the Copalum people. (CPSC is a political organization so draw your own conclusions) Recently King Innovation has come out with the Alumiconn device that is an aluminum lug style device and I haven't heard anything bad about it yet. Since this is basically the same technology as we had in aluminum lugs for years it should work fine and you don't need any special tools or training.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 12 Apr 2008 10:50:37 -0400 snipped-for-privacy@aol.com wrote:
| Virtually all of the "aluminum" problems were workmanship related. | There was a problem with the binder screw devices and the expansion | rate of the screw metal vs the wire. That was fixed with the CO/ALr | device which uses a screw wityh a bigger head and an alloy that | matches the wire expansion rate. When aluminum wire is used in an | aluminum lug all of this is eliminated and it will actually perform | better than copper. Most lugs are aluminum. That is why it hasn't been | a problem in larger wire sizes. The Noalox is mostly a fewel good | prodfuct and it is not required in the listing of any lug I know of | but it is "recomended" by some.
So does that mean Co/Alr devices will have a _different_ expansion rate than copper?
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 12 Apr 2008 18:43:10 GMT, snipped-for-privacy@ipal.net wrote:

Yup, but I doubt it will be a problem. Copper is more forgiving
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@aol.com wrote:

Comments apply only to US 15 & 20A branch circuits.
After known problems with aluminum wire connections (which resulted in UL delisting of aluminum wire and devices until new standards were written) the Consumer Product Safety Commission contracted with an *independent laboratory* to do extensive tests of aluminum connections. Over 7000 connections were tested. The testing showed properly made connections could fail.

CO/ALR devices used with the new alloy wire, required in the revised UL standard, eliminates expansion problems. Most of the aluminum branch circuits are "old technology" wire with a higher expansion rate. The CO/ALR devices are not tested with "old technology" wire.

The extensive testing of aluminum connections resulted in a recommendation to apply antioxide paste then abrade the wire. Oxide was a cause of failure of aluminum connections. Antioxide paste is an important element of reliable connections (15 & 20A).

The testing done under a *professional engineer* by an *independent laboratory* found that Ideal65 wire nuts were not any better than other wire nuts used with antioxide paste.
I have not seen a "30 year old CPSC article".
There is a paper, revised in 2007, at on options for aluminum wire: http://www.inspect-ny.com/aluminum/alreduce.pdf This paper was written by the *professional engineer* involved in the testing by the *indent laboratory* and is based on those tests. I know of no equivalent testing. The paper has never been published by the CPSC.
There is further information on Ideal65 wire nuts in the paper. Ideal65 does not solve oxide problems.

Preliminary independent testing looks like these are reliable, for the reasons you give.
--
bud--

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.