Appliance Cord Short Circuit

First a little history about this heater. This ceramic heater was used almost daily by my son. He would sit in front of it every morning. If our home was 80 degrees I believe he would still use it. My point is that this heater was plugged in and out more than usual. As you can see by the bent prong it was obviously yanked out of the receptacle in which it was plugged. I was sitting across the room working on this web site when my son plugged the heater in. He turned it on and sat in our recliner to watch tv. After it ran for a couple minutes a sizzling sound came from the cord immediately followed by about a three inch tall white-blue flame. The flame burned long enough for me to run across the room and yank the cord out.

This is exactly the type of electrical fault that burns houses down. This could have happened even if the heater had been turned off. The power travels up the cord inside the heater to the on/off switch. The cord would have shorted the hot and neutral wires together due to the twisting and pulling on the cord over the past few months. An Arc Fault Circuit Breaker is designed to detect this type of fault. If this circuit had been on an AFCI breaker the power would have been disconnected before the flames started shooting, possible before we could have noticed anything at all. It may have created a nuisance with the breaker tripping but we would have been safe. You can read more about the AFCI circuit breakers by reading the article HERE.

This circuit was connected to a regular 15 amp circuit breaker which never tripped. Why didn't the breaker trip? Regular circuit breakers are thermal devices. A load must be applied to the circuit which pulls power through the breaker. As more current travels down the circuit heat builds up. When the heat reaches the threshold of the breaker design it opens the circuit, disconnecting the power. This cord either didn't pull enough current or didn't pull the current long enough for the heat to build up at the breaker location. This type of thermal load can be a problem on long circuit runs. The further away the breaker is the more heat must build up to trip it.