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Old 08-06-2008, 01:12 PM   #1
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GFCI Question

My house is ungrounded. I know that receptacles that are ungrounded provide no protection to the things that are plugged in. I've heard from some people that GFCI's help, and I've heard they do nothing. My question is, if the GFCI receptacle is grounded, does that provide better protection for the entire circuit downstream of the GFCI? Or is it just providing the same protection downstream as if it were not grounded.



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Old 08-06-2008, 02:04 PM   #2
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Yes everything else downstream will have GFCI protection provided that the device is wired correctly. The GFCI would also need to have the ungrounded sticker that comes with put on it.


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Old 08-06-2008, 02:09 PM   #3
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Originally Posted by dankreboot View Post
My house is ungrounded.
I've heard from some people that GFCI's help, and I've heard they do nothing
"The only way to deal with an opened can of worms is to get a bigger can.

I will only say that for the GF device schematics that I have seen, the GF doesn't "know" about ground; it only measures the difference between the current going out and the current coming back.
It should protect grounded people in your ungrounded house from shock.
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Old 08-06-2008, 04:50 PM   #4
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Ungrounded appliances are all the more reason to install GFCI receptacles!
Definitely worthwhile.

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Old 08-06-2008, 06:59 PM   #5
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Joining the GFCI recommendation

Ground and GFCI provide different protections

Ground avoids electrical shock in some cases. Say a hot wire inside your computer power supply has damaged isolation and it touched the metal. The entire computer box becomes hot now and will shock you if you touch the USB port or something. If the computer is grounded the current will flow to the ground effectively creating a short circuit and tripping a breaker. This will happen as soon as the fault appears and before you happen to touch it yourself

GFCI stops a shock as soon as it detects it. It is made to do this fast enough before you get harmed. In the same story with the computer - it will continue to work untill you touch it. When you touck you will get shocked and the GFCI will shut down quickly preventing prolonged shock for a dangerous amount of time

A third way to protect is separating transformer (used in some shaver sockets). This thing avoids shock by separation of the AC source from the ground reference. If you touch a wire on the output of isolating transformer and ground then no curret will pass through you. Disadvantages of this thing are constand power dissipation (it wastes power even when nothing is plugged in. can be solved by switching off completely when not in use) and usually load carrying capability is quite limited. You also need separate transformer for each socket and the use of splitters with such transformer is forbidden. But they are probably the most powerful protection for the most dangerous cases like sockets above pools etc
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Old 08-06-2008, 08:33 PM   #6
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It depends what you mean by "Protection." A GFCI will protect against electrical shock even without an equipment grounding conductor. but you need to have an EGC in order for a plug-in surge suppressor, or surge suppression circuitry built into a device, to effectively protect against equipment damage caused by surges.


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