Part 2: Aluminum vs. Copper Conductors-What’s Best for Your Facility?


Overcoming Installation and Design Challenges

Installation

As with any material, particular challenges come with installing aluminum in your facilities. Installation criteria exist to ensure the proper operation of the electrical distribution system. Connections for aluminum are more critical than for copper. Although these installation steps are not complicated, they are indeed different from copper installation and need to be followed per instructions. When connections are made correctly, aluminum conductors run at a lower resistance and, therefore, at a lower temperature than copper conductors.

These steps can help you achieve proper installation when using aluminum:

  • A proper stripping tool should be used to avoid damage to the conductor.
  • The installer should be aware that aluminum is prone to forming a very thin oxide layer that is created within a few seconds of air exposure. For this reason, the conductor must be cleaned with a wire brush to remove this oxide layer. Then an antioxidant joint compound such as NO-OX or Penetrox must be applied to keep the oxide layer from forming.
  • The connections must be torqued to the manufacturer's recommendations. Failure to tighten the connections properly could result in an open circuit or arcing problems. However, terminations must also not be over-torqued, and they should not be tightened annually. Doing so reduces the current carrying capacity through deformation and causes a hot termination.
  • Make sure to use aluminum-rated, two-hole compression connectors. Mechanical connections are not a suitable connection type because of the expansion properties of aluminum. However, some vendors disagree, claiming field electricians have more trouble using the wrong dyes in crimpers than with misusing the mechanical connectors. In either case, pay close attention to the details of lug installation. This design may cause some spatial concerns with some equipment, e.g., panelboards.
Design Criteria

Another design issue challenge is that aluminum cannot directly terminate to motors due to the current UL listing limitation on motors. This limitation can be overcome by running aluminum to the disconnecting means and running copper to the motor. Using a pigtail or adapter from aluminum to copper and vice versa is also a viable option. However, this technique probably requires additional space at the motor junction box.

Although the improved design of newer aluminum alloys has allowed their conductivity properties to increase, the conductivity of aluminum is still only about 80 percent of copper's. Because of this, aluminum cables must be larger to allow for the same current-carrying capacity as its equivalent in copper wire. Raceway sizes need to be checked and often increased; it is usually necessary to increase the conduit sizes on about 5 to 7 percent of runs. The conduit size often remains the same, but it still must be checked on a case-by-case basis.

Today, aluminum cable is commonly compact stranded, compensating for some of this loss in conductivity due to a tighter packing of aluminum strands per cable diameter. Therefore, the aluminum wire can be made smaller than usual to meet ampacity requirements. Also, conduit sizes do not need to be increased as often, explaining the relatively low figure of only 5 to 7 percent of runs being increased.

Quality Control Procedures

Implementing quality control procedures and thorough documentation is vital when using aluminum in your facilities. Good, non-destructive infrared testing and inspection are essential for any electrical distribution system, whether aluminum or copper. Systems should be inspected by qualified personnel at energization and again at 30 to 60 days after startup to determine early problems under full load. Annual follow-up inspections are also an excellent practice to employ.

Conclusion

As with any significant change, there are risks involved in selecting aluminum for your design. You must weigh the pros and cons of aluminum vs. copper and ultimately decide based on each of their propositions. Finding an experienced electrical construction and engineering company like Interstates will help you make an informed decision. Further, using a trusted installer means having properly trained field personnel who make good connections, reducing service calls and potential downtime.

We don't recommend that every project utilize aluminum conductors. The research we performed is aimed at helping our clients evaluate the opportunity and decide for their specific situation based on solid information and our recommendations. We want clients to know that there are financially beneficial options available to them, and one of those just may be using aluminum in their facilities.

Using aluminum at all in industrial projects may be a significant change for some, but every project can be evaluated for this cost-effective option. The availability of alternative materials, at the very least, is an opportunity to examine the marketplace and make specific decisions about value for each unique facility.

Where Can I Learn More?

Interstates can help you make informed decisions if you're interested in using aluminum. If you have any questions about the best materials to use in your facilities, contact us.

Find Part 1 of this blog here to learn about the potential benefits of using aluminum in your plants.

Brent Kooiman, Senior Project Engineer


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