EC grade copper and other metals for electrical and power distribution work

EC stands for electrical conductor. In practice it means electrolytic tough pitch copper with a minimum of 99.90% copper (silver counted as copper) and conductivity close to 100% IACS in the annealed condition. Lower 'commercial' copper with more impurities can lose several points of conductivity, which is invisible to the eye and obvious on a thermal camera. Our EC grade copper comes with a test certificate showing the chemistry.

EC copper flats and bars are the standard bus bar material in LT panels, MCCs, PCCs and bus ducts. Rods and strips go into transformer leads, links and windings.

The same copper comes in different tempers and finishes, and each does a different job.

• Hard drawn copper keeps its shape and strength, so it suits bus bars, overhead conductors and earth rods that must not sag.
• Soft annealed copper bends easily without cracking, for flexible links, braids and windings.
• Tinned copper resists oxidation and sulphide tarnish, so joints stay low-resistance in humid or polluted air, and it is the usual choice where copper meets aluminium.
• Nickel-plated copper holds up at higher temperatures and in corrosive atmospheres, for terminals near heating elements, furnaces and chemical plants.

Aluminium bus bar has around 61% of copper's conductivity, so it needs about 1.6 times the cross-section to carry the same current. Because aluminium is less than a third as dense, that larger bar still weighs roughly half as much as the copper one, and usually costs less. Bus ducts and large distribution panels often use aluminium for this reason. Copper wins where space is tight, short-circuit forces are high or joints are frequent, because aluminium joints need more care to stay tight.

Mixed systems are common too: aluminium bus duct feeding a copper-busbar panel, or aluminium cable lugged onto copper bars. At every such junction use bimetallic lugs or tinned copper with the right washers, and torque the bolts to the panel maker's values. Most hot joints found during thermography surveys are bimetallic joints that were assembled like copper-to-copper ones.