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Resistance Heating
Loose Connections
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Resistance Heating
Loose Connections
Loose connections can be the source of high-resistance heating. In one study [1], the author found that “glowing connections” of copper and aluminum wiring would readily occur when a steel screw securing their connection became loose. In over 100 experimental attempts, glowing occurred if the steel screw was backed off 1/8 turn from a torque of 2 in-lb. Glows were also produced in the lab when broken parts of electrical wire contacted each other. Glows did not occur with tight connections, but if the steel screws were loosened, glows were obtained without any unusual environment, foreign substance, corrosion, or surface coating. This study focused on 120 volt AC circuits, but confirmed the results for DC circuits of less than 10 volts. The course authors’ testing has qualitatively confirmed the results for 12 volt DC circuits as well.
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