- Safety Corner | May 23, 2013
Making terminations should be high on the list of good examples for the meaning behind the statement "the devil is in the details.” This task may seem simple but mistakes here could cause hours of troubleshooting or other types of problems after continued hours of use and aging of the installation. Let’s explore, from a high level, what you must concern yourself with when terminating conductors. I think you may see that this task, which quite often is left to the most inexperienced on the job, may need closer attention.
There may not be an immediate cause and effect when it comes to terminations gone wrong, as some problems may take quite some time to manifest themselves. Take the problem in Figure 1 as an example. This picture shows the use of an incorrect lug on a Photovoltaic panel. The dissimilar metals have caused corrosion to occur over time. I am quite sure that when it was first installed it looked great, but time has revealed the problem. The following are some, not all, of identifiable problems that poor terminations can cause.
Heat: Loose connections due to not being torqued properly can introduce impedance that reacts with the current to cause heat. The heat only acts to further degrade the connection point. Excessive heat at a termination can damage equipment on either side of the termination whether it be the insulation of the conductor or the equipment to which the conductor is attached.
Oxidation: Aluminum quickly develops a layer of oxide when exposed to air. This oxidation is highly resistive. Proper plating is required or the use of other paste-type products applied on the termination.
Corrosion: Dissimilar metals can introduce corrosion as shown in Figure 1. This acts to introduce more impedance into the circuit and if this connection is your ground return path or an equipment grounding system, your path of least resistance can be com-promised and your grounding system is not quite as effective as you had hoped. Corrosion can occur in aluminum conductors due to galvanic action, which occurs if dissimilar metals are used in an electrolytic solution.
Thermal Linear Expansion Coefficient: The fractional change in length of a particular material, for each degree of temperature change, can cause loose connections, which could result in heating.
Creep: Creep is the continued deformation of material under stress.
Voltage (Over/Under): If a termination is not made correctly and the wire to the load or from the source does not make the connection needed, you may experience a reduced voltage or even an overvoltage. Your overvoltage condition is a good example of losing the neutral on the line side of a residential home’s main loadcenter. I have had seen a handful of examples of this on homes where the neutral from the utility either in the meter or even at the transformer caused an overvoltage in the home, damaging electronics.
Arcing: Arcing from phase to phase, phase to neutral, or even phase to ground can occur if bare conductors touch equipment or touch other bare conductors. Stripping the insulation from the conductor before termination and damaging the insulation during termination can introduce opportunities for arc faults to occur.
NEC Violation: There are many areas in the National Electrical Code that focus on termination points. When mistakes are made, an inspector just may be able to point out the problem and the NEC Section it violates.
Miss-Operation: Improper voltage, high impedance paths, and arcing and sparking as well as other effects of poor terminations may cause equipment to not operate as expected. Whether it be sensitive electronic equipment, industrial control equipment, or a grounding system solution or more, mistakes in terminations may be a cause of miss-operation.
Violate UL Listing: If care is not taken in your terminations, you may be applying the product outside of its UL listing. Products are tested under certain conditions and test configurations. These are reflected in manufacturer instructions and can be found in