This depends on the pitch of the roof. For 3-4 degrees 14.6m, for 4-10 degrees 11.0m, for 10-30 degrees 9.7m and for over 30 degrees 8.1m.
There are several reasons. Firstly, the bars are more compact because copper has a higher conductivity than aluminium. Secondly, it is much easier to joint copper. A hard, highly insulating oxide grows very rapidly on the surface of aluminium, making it very difficult to make good reliable joints in the field. On the other hand, the thin oxide layer that forms, more slowly, on copper is not an insulator so jointing is simple. Finally, copper is much stronger than aluminium, less susceptible to creep and better at withstanding short circuit current forces.
Condenser coils with round copper tubes and aluminium fins have been a winning combination for ACR coils for many years. Manufacturers enjoy the assembly advantages provided by these components while technicians find it easy to join and repair copper tubing in the field. More importantly, this well established technology has a proven record of durability in the field resulting in a high level of customer satisfaction.
Smaller diameter tubes allow for more effective heat transfer.
Yes, copper is as vital as calcium, iron and zinc. An adult needs 0.9mg of copper every day to maintian good health. Nuts, seafood, wholegrain cereas and offal are good sources of copper and a balanced diet should provide adequate copper.
Yes, it has been used for many years. However the nitrous oxide fumes given off when absorbed into surrounding fabric create a fire hazard. Also energy is used in the heating process. Better to patinate cold or use prepatinated copper.
Gunmetal or dezincification resistant brass.
No. Copper is not susceptible to precipitation hardening.