The Overloaded Extension Cord
During a pre-incident walkthrough of a warehouse, you see a 16-gauge extension cord running about 40 feet from a wall outlet to a space heater rated at 1,500 watts. The cord is warm to the touch near the plug, and it runs under a rubber mat and through a doorway where the door has been closing on it. A worker says the cord has been in place for months and "only gets warm sometimes." The outlet is on a 15-amp circuit shared with two fluorescent light fixtures and a small refrigerator.
1. Using the numbers given, explain why the cord is a hazard and identify the most likely failure point.
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A 1,500-watt heater on a 120-volt circuit draws 1,500 ÷ 120 = 12.5 amps. A 16-gauge cord is typically rated for about 13 amps for short runs, so the heater alone is near the cord's limit, and the 40-foot length adds voltage drop and resistance heating. The cord is also warm, which is a sign of resistive heating.
The most likely failure point is where the cord is damaged or compressed: under the mat and at the doorway where the door closes on it. Repeated flexing and pinching breaks strands, raising resistance at that spot and concentrating heat. The plug end is also suspect because a warm plug suggests a loose connection.
2. The circuit is 15 amps and already carries lights and a refrigerator. What does that mean for the total load, and what should you recommend?
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The heater draws 12.5 amps. A 15-amp circuit should not be loaded above 80% for continuous loads, which is 12 amps, so the heater alone exceeds the continuous-load guideline. Adding lights and a refrigerator pushes the circuit toward or past its breaker rating, which can cause nuisance trips or, worse, sustained overload heating at connections.
Recommend: remove the heater from that circuit, plug it directly into a wall outlet on a dedicated circuit if one exists, replace the 16-gauge cord with a properly rated 12- or 14-gauge cord if an extension is unavoidable, reroute it out of the doorway and out from under the mat, and have an electrician evaluate the circuit loading.
3. The worker says the cord "only gets warm sometimes." How should that statement affect your judgment?
Read the worked answer
"Sometimes" is consistent with intermittent high load, such as when the heater cycles on and other appliances run at the same time. Intermittent heating is not reassuring; it means the cord reaches a hazardous condition repeatedly without being noticed. Warmth at any time indicates the cord is being pushed near or beyond its capacity. The correct judgment is to treat the cord as a hazard now, not to wait for it to fail visibly.