Exploratory study of glowing electrical connections

The extent to which loose electrical connections in residential-type branch circuits have overheated in a laboratory was described and characterized. With loose electrical connections, which conceivably could be inadvertently duplicated in field installations, but with otherwise normal installation and operating conditions, visible glows were observed under laboratory test conditions in normal 120-volt, 15 and 20 ampere branch circuits with both copper and aluminum wire. Characteristics of the glow condition were differentiated from arcing/sparking as sometimes observed in making or breaking electric circuits. Glowing electrical connections may dissipate as much as 35 watts of power with a current of 15 amps in the circuit and as much as 5 watts with a current of 0.8 amps in the circuit. Temperatures over 750 F were measured on the 'break-off tab' of receptacles.