A mechanical lug is a connector which is used to connect cables. Mechanical lugs form a crucial part of an electric system. Mechanical or bimetallic lugs are generally made up of from either of two metals – aluminum or copper.
Back in the decade of 60s, aluminum wires were generously used in the wiring system f almost every office. Since the electrical cables were made up of aluminum, it makes sense that an electrician would use an aluminum lug at the joint connections.
Misery for the electricians, they went through a lot of terminal catastrophes. Connections were started to lose at the junctions where aluminum lugs were being used. As an outcome, electrical fires started to occur consistently. Electricians were unable to know why the failure was happening. Since, in their opinion, aluminum is a good conductor of electricity.
When the fires become more frequent to happen, it was concluded that the source of failure is the use of aluminum lugs. Electricians tried to utilize copper wires with aluminum lugs and copper lugs with aluminum wires; no combination worked. Subsequently, it was agreed that aluminum is not the right element for electrical wiring. That is when copper made its way as an adequate replacement as terminal lugs.
Without going deep into the technicalities; what you need to know is the co-efficient. Higher coefficient signifies a high risk of fire. Besides, copper has a massively low coefficient of thermal expansion.
Copper lugs and bimetallic lugs, do not create much fire hazards. Wiring system based on copper is now used all around the globe. There is a reason because copper has got almost everything that is required. Aluminum happens to be inexpensive as compared to copper. However, wiring and copper lugs are a bit expensive than aluminum.
It is a fact that in early days, aluminum was not the correct choice for best terminal lugs. Since then, the preferred alternative was copper as lugs. All things taken into consideration, it is much safer to use aluminum lugs now in comparison with earlier days. Late innovations on aluminum made them as secured as copper. You can now find aluminum lugs with a copper coating. Aluminum is inexpensive but can cause danger. However, copper demands additional money.
There is not a clear cut answer. It will take time before people starting to put faith in aluminum as they now have in copper.