AFCI

[SamC]

I have a idea what AFCIs are suppose to do, but how do they really work. Do they detect arc faults between line and neutral, line to ground? Will a small arc on a portable space heater thermostat trip the AFCI?

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[electric-ed]

Sam, They have electronic circuitry that can recognize the unique "signature" of arcing at a loose connection. This dangerous arcing is different in waveform than the arcing that occurs when you screw in a lightbulb with the power on, for instance. I'm not sure how sensitive they are. They are designed to detect both series and parallel arcing. Series arcing does not result in an increase in current, so a fuse or breaker does not see it as a fault. A GFCI will only trip on a fault to ground, so it looks like we need this new technology.
Click this link for some diagrams relating to this topic. http://www.electric-ed.com/images/Afci.gif

Electric Ed

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[This message has been edited by electric-ed (edited January 07, 2002).]

[SamC]

Thanks for that bit of information on AFCIs.Do
you know if they will be required on new wiring installations only or are we going to have to install them on bedroom circuits when we upgrade fuse panels to breaker panels.I think they are a great idea, but from past experience
in some older homes bedroom circuits are shared with other parts of the house. This could lead to having more AFCIs then required,thus increasing the cost of panel upgrades.

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