Aluminum vs. Copper

[bidaw]

Question - I have read that copper is prefered over aluminum for wiring up high current applications. Can someone here explain to me if this is a hard fast rule?

The reason that I ask, is that I have an opportunity to purchase upward of 300' of 3/0-4 stranded aluminum cable. So stripped, that would give me up to 1200' of cable (oh btw, at .75/ft for all or 1.00/ft for lesser quanity).

I was told not to mix in the connections - the different alloys, but if it is isolated, would there be harm?

This pricing is crazy...so I am hoping to get an answer that is favorable for purchasing!!!

Thanks in advance...

[Mike90250]

Aluminun wire is fine, as long as you use the proper connectors and AL rated anti-ox grease at the connections. I have several thousand feet of #2 and # 4 installed in various places, but all have been spliced/terminated with rated splice blocks and terminals/breakers. Modern aluminum wire alloys are much better that the alloys used for the house wires in the 60's that caused all the fires.

Just remember, the resistance of AL is higher than CU, and you need to upsize the wire gauge about 2 sizes, so while #8 wire would work for copper, you would use #6 for AL in the same application.

The wire / voltage caculator in my .sig has option for AL or CU wires.

[bidaw]

Thanks! This gives me motivation to start thinking of what type of project I would use it for, and how much of it I will need!

This really helps in the wallet.

[peakbagger]

One caveat is that I avoid aluminum in corrosive atmospheres (like seashore applications). I used to have to work at a industrial wastewater treatment plant and despite the original installers using good installation practices, junction boxes and motor control center terminations were always pretty crusty.

[Mike90250]

One caveat is that I avoid aluminum in corrosive atmospheres (like seashore applications). I used to have to work at a industrial wastewater treatment plant and despite the original installers using good installation practices, junction boxes and motor control center terminations were always pretty crusty.

And I've had the opposite experience, when working on my old house, with copper wire from the 40's, the entire body of the wire (10 ga solid) was brittle, black, and oxizded all the way through. Somehow, it was still conducting. I had to remove several sections back to the fuse box (2, 30a fuses for the whole house) and replace with new copper. (this was shortly after the aluminun wire ban, before the newer alloys.)

Aluminun develops an oxide layer within seconds of being fresh cut and exposed to air, the "grease" for connections is loaded with zinc crystals which cut through the oxide as you rub it in, and the grease prevents air contact.

Of course, seashore environs, they say to use tinned (solder or tin coated), over pure copper wire, to increase the salt resistance. Copper will corrode through quickly in salt air.

[solarpowered]

Aluminum conductor seems to be more the typical install material for solar contractors these days.

1.Its cheaper and the price doesn't fluctuate to market volatility as frequently as copper does.
2.It also doesn't get as good as a redemption value to recycle it either, less likely that thieves will steal it.
3.Maintenance is a PITA so its best to leave as little exposure to the elements as possible.
4.Lugs cost a tad more because of sizing, and enclosures would have to be larger for service loops and radius

End result is that its 1/3 the price of copper so for large scale projects there are alot of cost saving benefits