Code limitation on the use of aluminum for bonding jumper?

[elec_eng]

Is there such thing on NEC? We are trying to use Aluminum conductors in favor of cost savings in a project we are working on and one of comments from the 3rd party reviewer is that all bonding jumpers have to be copper due to the code limitation on the use of aluminum for bonding jumpers.

I don?t recall such limitation on the code but I don?t use aluminum conductors very open so I may have overlooked this. Is he correct?

 

[Gregg Harris]

Is there such thing on NEC? We are trying to use Aluminum conductors in favor of cost savings in a project we are working on and one of comments from the 3rd party reviewer is that all bonding jumpers have to be copper due to the code limitation on the use of aluminum for bonding jumpers.

I don?t recall such limitation on the code but I don?t use aluminum conductors very open so I may have overlooked this. Is he correct?

250.102 Bonding Conductors and Jumpers. (A) Material. Bonding jumpers shall be of copper or other corrosion-resistant material. A bonding jumper shall be a wire, bus, screw, or similar suitable conductor.

 

[elec_eng]

Does that eliminate aluminum conductor? Aluminum is not qualified for other corrosion-resistant material?

 

[GoldDigger]

Does that eliminate aluminum conductor? Aluminum is not qualified for other corrosion-resistant material?

Aluminum, in isolation, is corrosion resistant. But the corrosion-resistant oxide coating is also an electrical insulator.
Aluminum in contact with other metals, notably copper and steel, in a damp environment can develop galvanic (electrolytic) corrosion.
Since the function of a bonding jumper is to provide electrical continuity, all of the recognized problems with Al-Cu connections in wiring devices will apply equally to use of Al for the bonding jumper.
Conclusion 1: Al is not suitable for use as a bonding jumper without similar requirements for listed fasteners, anti-oxidant coatings, etc to those for general wiring and interconnections.
Conclusion 2: If the corrosion resistant material clause is not sufficient to prevent use of Al for bonding jumpers and the general restrictions on use of Al in wiring do not prohibit this use, there should be explicit language added to the code to do so.

PS: The mental image of an aluminum screw as a bonding jumper cracks me up.

 

[Gregg Harris]

Does that eliminate aluminum conductor? Aluminum is not qualified for other corrosion-resistant material?

No it does not eliminate aluminum conductors. Aluminum is only exclude in a corrosive atmosphere or within 18 inches of the ground.

 

[infinity]

No it does not eliminate aluminum conductors. Aluminum is only exclude in a corrosive atmosphere or within 18 inches of the ground.

I agree and Table 250.66 used to size GEC's and bonding jumpers lists Aluminum as a permitted conductor.