[londons_explore]

Notably, China seems to make use of aluminium wires which are copper plated.

They're cheaper than pure copper, and the plating means they don't have the fire problem - since it is always the copper surface that makes contact in any joint.

I don't know why we don't use them - they would make electrical jobs cheaper, and mean we can afford to upgrade in other ways - like for example having every circuit powerful enough for a dryer rather than needing a special dryer circuit.

[owenversteeg]

I built a boat partially with CCA (copper clad aluminum) wire, disregarding the recommendations to not use it. I didn't give it much thought and naively figured that as copper and aluminum are two of the most "rust-proof" materials that it would be fine. Within two years of using it - and before the boat even made it into the water - it had begun to seriously corrode to the point that resistance was significantly increased. I had to replace all the CCA wiring and terminals connected to it.

Basically, both copper and aluminum are "rust-proof" because they develop a thin, hard layer of oxide immediately upon exposure to air. However, this also means that when a new crack forms (by vibration of the wiring or thermal expansion for example) that crack will be immediately coated by an oxide layer. At the same time, moisture in the air will create a galvanic cell with the copper as cathode and aluminum as anode (because aluminum is more active, more willing to give up electrons, which is because its bond with its electrons is weaker than copper's.) As the electrons leave the aluminum it develops a positive charge, which attracts negatively charged oxygen.

It is this last effect, galvanic corrosion, which I believe to be the chief issue with CCA wiring. Copper and stainless steel, for example, are much closer in the galvanic series than copper and aluminum, so copper and aluminum corrodes significantly faster.

Unfortunately, galvanic corrosion is a tough one, because lots of modern American houses are built with poor ventilation - as you can see by the large number of homes with mold issues. That moisture is exactly what enables galvanic corrosion. I think if we used CCA wiring across America we'd see a number of house fires caused by moisture -> corrosion -> higher resistance -> heat -> fire.

[organsnyder]

I'd be concerned about what happens when the wiring gets nicked up when the connections are being made.

It seems like if we want to achieve the goal you mention, we could switch over to 240v like much of the rest of the world.

[ethbr0]

I am not an electrician, but wouldn't all US wiring already be 240v-compatible (at currently rated amperages) if the connectors were upgraded?

US residential has 240v at the home fuse box from the upstream 3-phase.

But I imagine it'd require a big adjustment at the utility level if everyone started drawing from +120v & -120v, instead of the current balance around the neutral.

[quickthrowman]

The vast majority of US homes use NM cable (romex) which is rated for 600v.

NEC 2020 edition, Article 334 Non-Metallic Sheathed Cable

334.104 Conductors.

The 600-volt insulated power conductors shall be sizes 14 AWG through 2 AWG copper conductors or sizes 12 AWG through 2 AWG aluminum or copper-clad aluminum conductors.

[ethbr0]

So the in-wall would be good, but the standard socket (NEMA 5-15) definitely isn't rated for 240v and would need upgrading.

[quickthrowman]

Correct, a residential NEMA 5-15 receptacle is only rated for 125v. There are some dual amp/dual voltage (15a/20a, 125v/250v) receptacles out there, but you almost certainly won’t see them in a house. NEMA 6-20 is rated for 20a at 250v.

More dual amp/dual volt wiring devices: https://www.plugsocketmuseum.nl/NorthAm1combi.html

[briHass]

Yes, it's the amps that matter for wire gauge (at typical voltages). Regular 12/2 or 14/2 NM cable (Romex) is used for US 240v circuits all the time. The only requirement is to color the white wire at the ends black or red to signify that it is a hot conductor with reference to ground.

[organsnyder]

I would think so, but I am also not an electrician. I'm guessing the biggest issues would be the chicken-and-egg problem of upgrading receptacles and devices, as well as the question of whether 240v is actually a prudent choice to begin with.

[ethbr0]

Isn't a big part of the problem the thermal expansion difference between aluminum and copper? (~20%)

Wouldn't that eventually cause mechanical adherence issues with dissimilar metal plating?

[londons_explore]

One would imagine so, but it seems it isn't a problem. Not sure why. Perhaps the elasticity of the metals is sufficient to absorb that change over typical temperature variations? Maybe they would fail if you poured liquid nitrogen over them?