Copper vs. Aluminum Conductors

[jmbelectrical]

I design low-voltage (Under 600V) power/distribution systems for residential, commercial, and industrial facilities. In the spirit of cost savings, electrical contractors often propose using aluminum feeders and aluminum busing material. We always specify all copper materials by default, but are usually willing to permit the use of aluminum in lieu of copper.

While literature that I came across indicates that aluminum is safe and significantly better than it used to be, I still have some lingering concerns regarding aluminum's coefficient of thermal expansion and susceptibility to oxidation. It is my understanding that, where aluminum conductors are used, mechanical-type lugs on switchgear are required to be re-torqued on a yearly (Or other manufacturer-recommended time interval) basis - a maintenance item that I'm sure gets overlooked at most facilities. Does the use of compression-type lugs remedy this? And with regards to oxidation, it is my understanding that anti-oxidation compound is typically applied at conductor terminations. How effective is this? Does it ever need to be reapplied?

Any input is greatly appreciated.

 

[7anoter4]

We use [Power Stations] Burndy compression connectors[for copper and aluminum conductors] for many years[design!].
No problem encountered[from customer feedback].As Burndy declares:
"Compression connectors are installed with various types of installation tooling such as mechanical, hydraulic and battery actuated tools.
Designed to be a "permanent" connection, compression connectors are the installation of choice when you want your connections to last.
Offering compression connectors used in both grounding and power applications, BURNDY® connectors are designed "hand in hand"
with application tooling to provide a guaranteed and long lasting solution so that you do not have to worry about your installations.
Regardless of your conductor types (whether you are using copper, aluminum, ACSR or AAAC to name a few) BURNDY®
offers connectors and tooling to tap, terminate or splice your conductors."
See:

http://www.burndy.com/solutions/cmr-mro/connectors.aspx

May be other manufacturer [equivalent] I don't know.

 

[WoodrowJWeen]

Regarding mechanical type lugs; I've been hearing the exact opposite from the cable manufacturers. They recommend not retorquing aluminum ever. That being said, we allow aluminum as a value engineering item from contractors for larger wire sizes, but require compression lugs or compression adapters at each connection.

 

[dpc]

For larger conductor sizes, if the mechanical connector is UL marked for AL/CU and the termination is made per manufacturer's instructions, I don't have any real concerns. If there was really a major problem with these connectors, it would have come to light long ago. I think the cold flow issues were essentially solved a couple of decades ago.

I've seen some really lousy compression connections made by electricians who did not have proper equipment, did not know what they were doing, were in a hurry, or some combination of these.