The construction' drawings are done, the specifications are complete, and bidding has commenced.  A few days before bids are due, however, the contractor suggests replacing copper conductors with aluminum conductors – a suggestion that may be a value-engineering line item, or a qualification item within the bid.  But what are the technical aspects of making this switch?

Is copper better than aluminum for conductors? If the performance is considered identical, why wasn’t the less expensive conductor specified? 

Both copper and aluminum are publicly traded commodities that are subject to price fluctuations on the open market.  

Therefore, on any given day, the price difference between aluminum and copper varies.

Generally, aluminum pricing is lower than copper―sometimes significantly, as shown in the following example for a 400 amp service:

Both materials are electrically conductive.  Aluminum, however, is approximately 60% as conductive as copper - requiring larger aluminum conductors to carry the same amount of electricity as copper conductors.

Historically, aluminum connections deteriorate over time because aluminum expands and contracts more than copper due to greater electrical resistance and resulting heat.  The conductor expansion and contraction may cause loose connections that, in extreme cases, lead to fires.  Utilizing special connections, paying extra attention during installation, and periodic maintenance will help avoid these problems.

In larger sizes (for relatively steady electrical loads and minimal connections) aluminum may be an acceptable alternative to copper conductors. Initial cost savings is only part of the equation. Proper installation, connections, inspections, and ongoing maintenance should be considered, as well.  As an example, since the early 1900s, utility companies have successfully used aluminum wire for transmission of electricity within their power grids.

Recommendations

For uses below 200 amps –

Copper is the better choice because there is minor cost saving (if any) by using the alternative: aluminum conductors.  Additionally, breakers, fuse blocks, and receptacles are listed to only terminate with copper and will not accept aluminum connections.

Between 200 and 800 amps –

Complete case-by-case study and evaluate the building characteristics such as voltage, distance, load variations and type of load.  Within installations of this size, aluminum can often be used from the utility transformer to the building distribution, then from the building distribution to the house distribution panel.  Significant savings can be achieved based on the distances involved.

Aluminum conductors often offer larger cost savings above 800 amps. For example, in one large multi-building lifestyle center project, the estimated savings to use aluminum instead of copper building service conductor was $100,000.

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For more information on determining Copper vs. Aluminum conductors, please contact CAHE Electric: info@ahecable.com