[sctdaily]

As a commercial electrician I was taught that terminations of Aluminum feeders had to be periodically checked for tightness due to 'creep' (the wire expanding and contracting due to changes in temperature). Is this a real problem? What is the recommended interval for checking the proper torque of the terminations?

[tkrussell]

All electrical equipment, including copper cable mechanical connections, bus bar bolted connections, circuit breaker bolted connections, etc. are recommended to be inspected and checked for proper torque values, periodically, usually annually.

This recommendation is from NEMA, IEEE, ANSI, and every manufacturer of electrical distribution equipment.n

Loose connections wire is not unique to aluminum. What is unique to aluminum is the soft characteristic of the metal, which gives the wire the false impression that it needs to be tightened frequently.

If you tighten a connection today, you surely can get a few more turns on the bolt or screw a few days later. All you are doing is crushing the wire, causing the metal to be pressed into any voids that may be in the mechanical connector.

This softness is not as noticeable with copper, so the impression is that copper is less apt to loosen while aluminum is more apt to loosen. If connections are torqued to the value listed on the mechanical connector, no more tightening is necessary.

High current loads create heat, which causes any metal to expand, and ultimately there is cooling, so the temperature changes of connections , along with vibration of equipment and just the nature of these metals cause any connection to loosen over time.

I manage a crew of electricians/technicians that perform these annual inspections using some high tech equipment, such as infrared cameras, ultrasound detectors, DLRO, (Digital low resistance ohmmeter), and millivolt DVM, to locate and quantify loose connections while equipment is both energized and de-energized. We have done this in paper mills, hospitals, data centers, foundries, office buildings, shopping plazas, etc, etc.

We even have one customer that hires a helicopter for us to inspect their couple hundred miles of power lines Which those by the way are all aluminum wire, and we find few problems.

While aluminum cable and bus is very popular, you may be surprised that most loose connections are found with copper wire and bus, and the typical brass,copper and copper alloy mechanical connectors. And you may be surprised that tightening a connection too much can be worse than a loose connection, review this page: The Loose Electrical Connection Myth