Copper Wire & Aluminium Wire ???

[ahmed osama]

mix of aluminum and copper wire

hi all

in some countries , the code saying that al. wire used in underground cables but the wires inside building must be copper

So i am asking why , what the diff. between the al. & copper wire??

what i know that the al wire have dia. greater than the copper wire at the same current

i want to know what about the safety & aging ..etc??


thx all

 

[flatulent]

The problem comes from the hardware inside buildings. They usually have copper contacts with the wiring. The bimetal contacts can cause heat and then fires.

 

[sigint]

To expand on Flatulent's comments, aluminum used with compression fittings is not safe, thermal expansion and subsequent contraction leaves voids in the connection that immediately oxidize - over time this repeated occurance creates a high resistance and resultant heat then sometimes fire - aluminum was used in residential housing for a short while with often disasterous results. It is now used in some applications with many precautions, making it too expensive for everyday use in buildings.

SiGiNT

 

[funster]

with same diameter, a copper wire has much less resistance than al. wire,

at the same time, copper's melting point is high than al.

so I think that's the reason.


best regards

hi all

in some countries , the code saying that al. wire used in underground cables but the wires inside building must be copper

So i am asking why , what the diff. between the al. & copper wire??

what i know that the al wire have dia. greater than the copper wire at the same current

i want to know what about the safety & aging ..etc??


thx all

 

[aland]

Size for size Cu beats Al any day. But weight for weight Al beats Cu. Thats why aerial conductors are Al -usually with a steel core so that it doesn't stretch under its own weight as its very ductile.

Al problem is that it oxidises very quickly, so joints are a big problem. Even the Al-Cu joint has to be set up correctly if exposed to weather, the Cu wire *must* be placed below the Al *or* Cu salts from corrosion will eat into the Al.

 

[gizzmo]

I owned a house that had aluminum wiring. It's possible to mix copper and al on a branch circuit, but you must use gray anti-oxidant paste + Cu-Al marrette connectors to avoid the risk of a house fire. The marrette connectors are very hard to find in the marketplace now, so it is best to avoid aluminum altogether, as it will eventually have to meet copper somewhere !