Aluminum wiring in homes have some rules that must be adhered to that you don't have to worry about when using copper wire. If you have to replace switches or outlet receptacles you need to find the type that is for use with your mobile homes aluminum wiring. They will be designated AL, AL/CU or CO/ALR. Most that you find are for CU or copper wire only. When stripping the wire do not scratch or groove the wire as this will cause weak spots and invite corrosion problems. I strongly recommend that you use an anti-oxidant compound. This is a corrosion inhibitor that you would sparingly apply to the bare wire before attaching to the screw down terminals (follow package directions). This compound can be found at most homes supply and hardware stores. I have a 1 once tube that has lasted a long time. It is also a good idea to apply it to aluminum wires that are attached to circuit breakers and is required by code. The use of aluminum wire was discontinued in 1976 in site built and manufactured mobile homes as small branch circuit conductors. Aluminum conductors are still widely used for main services and appliance circuits. Electrical service main wiring is usually aluminum to save costs.
Problems and Dangers of Aluminum Wiring in Homes
The biggest problems of aluminum house wire is that it is very soft and this tends to cause the bulk of problems. Aluminum wires in the breaker box, receptacle outlets and switches will eventually get loose. Therefore the connections need to be remade. Do not just tighten the the lug screw on the circuit breaker or the terminal screws on an outlet or switch. The best thing to do is to cut off the end of the wire and strip the end to get a new connection. Again I recommend using, and it is required by most local codes, to use anti-oxidant compound on the connection point. Be sure not to over tighten the screw and damage the wire. I strongly advise against using the quick wire holes on the back of any outlet or switches, use the screw terminals. Aluminum wiring also requires that when capping any junctions you make that wire nuts made for use with aluminum wire be used.
Aluminum Wire Sizes
As a general rule of thumb aluminum conductors have to be one size larger than copper wire to carry the same amount of current. As an example #14 copper can carry 15 amps it would take a #12 aluminum wire to carry 15 amps. As the current demand gets higher this changes. In the case of service entrance wiring a 2/0 copper wire will handle a 200 amp service a 4/0 aluminum wire is needed to carry the same current, this is double the size. Almost every service entrance job I have done has been with aluminum conductors unless it was specified copper in the homes architectural specifications. Aluminum is a lot cheaper and easier to work with than copper wiring on large appliance circuits.