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Residential Wiring - The Right Way!
Electrical Wiring and Safety
GFI Outlets / Circuits
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What they do is they are designed to sense when there is a leakage of current to ground, it senses when the ungrounded (hot) current feed and the return current are not equal which means that the difference in current must be going somewhere, such as through a physical person. It will trigger shut down an outlet or circuit when as little as .005 milliamps is leaked to ground. When any minute leakage is detected the outlet / circuit is shut down preventing a person receiving a lethal shock.
GFI protection is required near water areas such as bathrooms and outside the home outlets. Most codes now require them in the counter area in kitchens. They are usually not recommended for Freezers / computers because of the loses that might be sustained in false trigger instances. GFI's saves lives, but they should never be relied on to overcome stupidity, use common sense and do not have any electrical item near or within reach of the bathtub, and the natural instinct is to grab the item that falls inside the sink full of water to save it, where in my belief you should be staying clear until you know the circuit power is cut. If the unthinkable happens GFI technology will hopefully save you but never tempt fake thinking that technology will always be there to save you from your own stupidity.
I have had problems with these when plugging in a block heater on a vehicle in they can be a pain in always triggering which defeats the purpose of plugging in the vehicle, part of the problem is that you have an exposed plug in the front of the vehicle that can get exposed to freezing rain / snow, and the outdoor extension cord being used may be left outside which again is exposed to the elements, which again can cause a moisture leakage to ground which triggers the GFI outlet, I am not sure how to solve this issue, but bringing inside the extension cord when not in use will keep that part dry, but keeping the vehicle side of the plug dry is another matter.
Onward power that is protected by the same GFI outlet...
As depicted in the above picture this will protect onward items such as regular outlets but if the GFI outlet is tripped it will shut down all onward items.
Onward power that is NOT protected by the same GFI outlet...
As depicted in the above picture, onward items are Not GFI protected, and will still be powered even if the GFI is tripped.
Not shown in the diagrams but all bare wires (equipment grounding conductors) gets connected together and to the grounding screw of outlet as well as the electrical box itself if metallic.
Make certain the circuit power supply cable gets connected to the LINE terminals as they could be differently laid out than depicted in the pictures here, they will be labelled on the outlet itself. The same with the LOAD terminals if onward protection is desired, onward protection must be connected to the LOAD terminals.
Written: Jan 16 2012
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Donald Kerr / Wiring Done Right