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Posted by Jeff Wisnia on May 15, 2006, 11:01 pm
RBM wrote:
> Like the other post said, you don't have an imbalance until something or
> someone creates the bridge to ground. Then the device trips
For the last time I'll say that I agree completely with all that. I
checked into this thread when I questioned this statement by PipeDown,
when he said:
********************
Use of a single GFCI or a GFCI breaker does not solve the problem of not
having a ground wire in the first place. If you use a GFCI receptacle
and connect several receptacles downsteam, you will get some GFCI
protection but not from current into ground (the ground tab on those
will still be open). Only at the GFCI receptacle itself do you get
virtual safety ground protection.
********************
If by "safety ground protection" PipeDown meant that the GFCI would trip
on an internal ground fault in an appliance I didn't believe it would
unless there was a ground lead connected to it.
As Goldwasser says:
**********************************
GFCIs and safety ground:
Despite the fact that a Ground Fault Circuit Interrupter (GFCI) may be
installed in a 2 wire circuit, the GFCI does not create a safety ground.
In fact, shorting between the Hot and Ground holes in the GFCI outlet
will do absolutely nothing if the GFCI is not connected to a grounded
circuit (at least for the typical GFCI made by Leviton sold at hardware
stores and home centers). It will trip only if a fault occurs such that
current flows to a true ground. If the original circuit did not have a
safety ground, the third hole is not connected. What this means is that
an appliance with a 3 prong plug can develop a short between Hot and the
(supposedly) grounded case but the GFCI will not trip until someone
touches the case and an earth ground (e.g., water pipe, ground from some
other circuit, etc.) at the same time.
*********************************
I'll say no more on the subject.
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"Life is like a sewer -- what you get out of it depends on what you put
into it."
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>>RBM wrote:
>>
>>
>>>The ground fault device and anything plugged into any outlets connected
>>>to the load side of it, will cause the GFCI to trip if any leak of
>>>current to ground occurs, regardless if the outlets are grounded. The
>>>GFCI does not need a ground connected to it to function
>>
>>Of course, but that's NOT what I asked.
>>
>>I was talking about (internal fault) leakage to the safety ground lead
>>(chassis) oF an appliance with a three wire cord and plug. And, that
>>faulty appliance is plugged into a GFCI outlet which does not have a
>>ground wire run to it. i.e. an outlet which would require the little label
>>stuck on it warning that there was no safety ground there.
>>
>>Take a look at Sam Goldwasser's diagrams and explain please how the GFCI
>>can sense internal leakage to the safety ground lead of the appliance if
>>the ground pin hole in the outlet isn't connected to anything.
>>
>>http://www.codecheck.com/gfci_principal.htm
>>
>>Jeff
>>
>>
>>
>>>
>>>
>>>
>>>>PipeDown wrote:
>>>>
>>>>
>>>>
>>>>>Use of a single GFCI or a GFCI breaker does not solve the problem of not
>>>>>having a ground wire in the first place. If you use a GFCI receptacle
>>>>>and connect several receptacles downsteam, you will get some GFCI
>>>>>protection but not from current into ground (the ground tab on those
>>>>>will still be open). Only at the GFCI receptacle itself do you get
>>>>>virtual safety ground protection.
>>>>
>>>>I think I understand you. But just to be sure, are you saying that even
>>>>without a ground wire connected to it the first GFCI receptacle would
>>>>trip if an appliance plugged into it equipped with a three wire cord and
>>>>plug developed internal leakage between hot and ground (or on the fancier
>>>>GFCIs also between neutral and ground.), but that you don't get that
>>>>level of protection on the downstream ones?
>>>>
>>>>I'd assume you wouldn't get that protection on the first receptical
>>>>either if there was no ground wire connected to it. I can't see where a
>>>>leakage current to ground would flow if there was no ground wire for it
>>>>to flow through.
>>>>
>>>>If what you said assumed there WAS a ground wire to connect to the GFCI
>>>>receptical then I agree with your statement, but that's prolly not what
>>>>the OP has, unless he's lucky and the wall boxes are grounded, perhaps
>>>>via the bare ground wire used in some of the old BX cables.
>>>>
>>>><snipped>
>>>>
>>>>Jeff
>>
>>
>>--
>>Jeffry Wisnia
>>(W1BSV + Brass Rat '57 EE)
>>"Life is like a sewer -- what you get out of it depends on what you put
>>into it."
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