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Over Tightened Cable Clamp

Case History F06-049

Smoke was seen coming out of the outside wall of a duplex condominium. Directly behind the wall was the kitchen. The Romex cable connected to the dishwasher in kitchen had overheated. The problem was traced to an over tightened wire clamp at the dishwasher's junction box. The electrical path was between the "hot" and grounding conductor (safety ground). The grounding conductor was not connected to the frame of the dishwasher. Even though the cable overheated and there was evidence that the conductors briefly came in contact with each other, the 20 amp circuit breaker never tripped. The abrupt changes in the condition of the cable were due to fiberglass batt insulation preventing the cable from cooling. Fiberglass batt insulation is often split and placed on both sides of a Romex cable.

For Maximum Resolution, Click on the Body of the Picture.

Photo: Damaged Power Cable to Dishwasher

Damaged Power Cable to the Dishwasher.

Photo: Damaged Power Cable to Dishwasher

Another View of Damaged Power Cable to the Dishwasher.

Photo: Power Cable Burnt from Inside

Damaged Power Cable (Romex) burned from the Inside
Bare Grounding Conductor.

Photo: Sharp Contrast between undamaged and damaged wire insulation

The Abrupt Change in the Condition of the Cable was due
to the Fiberglass Batt Insulation.

Photo: Nicks in Conductors

There were nicks in the conductors where contact was made.
The nicks were found by finger tracing the conductors. .

Photo: Kitchen


Photo: Bottom of Dishwasher

Bottom of Dishwasher.

Photo: Back of Cable Clamp

Over Tightened Cable Clamp. Pot Metal melts at around 800°F.

Front of Cable Clamp

Damaged Wire Insulation at the Front of the Cable Clamp.

Photo: Safety Ground Not Connected

Safety Grounding Conductor Not Connected to the Grounding Screw.


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