What is one requirement for the metal points of contact in bonding jumpers?

The requirement that the metal points of contact in bonding jumpers must be free of nonconductive coatings is crucial for ensuring electrical conductivity and maintaining effective bonding. Bonding jumpers are intended to create a low-resistance path for electrical current, which is essential for safety and for preventing the buildup of dangerous voltage differentials.

If metal points of contact were coated with nonconductive materials, this would inhibit the flow of electricity through the jumper. It could potentially create points of high resistance or even prevent current from flowing altogether, compromising the effectiveness of the bonding system. Therefore, the requirement that these points be free of any nonconductive coatings ensures that an adequate and reliable electrical connection is achieved, allowing for the proper functioning of the electrical system and enhancing safety.

On the other hand, coatings can be helpful in other aspects of electrical installations, such as protecting against corrosion, but they must not interfere with the electrical conductivity at connection points in bonding applications.