I have a question for the electrical people. When replacing an old duplex receptacle with no grounding slot in existing construction that does not have a grounding conductor, I believe the NEC allows for the use of a GFCI properly labeled "no ground." I realize this is not ideal but allowed rather than having to replace the entire circuit.
First question might make my second question a moot point. Am I correct with the above statement?
Second question is why does NEC allow this?
My understanding of how a GFCI works in simple terms is that it monitors the current flow on the ungrounded and grounded conductors for an imbalance in excess of 4 or 5 mA and if detected immediately opens the circuit.
Couldn't this still potentially expose a person to a ground-fault situation? Suppose an appliance like a microwave is plugged into a GFCI that is not wired with a grounding conductor and a ground-fault becomes present within the microwave resulting in live power on the exterior of the oven. Since there is no grounding conductor, the current flow would have only one path and that is through the grounded conductor unless some other form of conductive material touches the exterior of the oven, such as a human.
The only explanation I can come up with is that the GFCI is expected to trip and open the circuit within about .03 seconds so this should be fast enough to protect the person.
First question might make my second question a moot point. Am I correct with the above statement?
Second question is why does NEC allow this?
My understanding of how a GFCI works in simple terms is that it monitors the current flow on the ungrounded and grounded conductors for an imbalance in excess of 4 or 5 mA and if detected immediately opens the circuit.
Couldn't this still potentially expose a person to a ground-fault situation? Suppose an appliance like a microwave is plugged into a GFCI that is not wired with a grounding conductor and a ground-fault becomes present within the microwave resulting in live power on the exterior of the oven. Since there is no grounding conductor, the current flow would have only one path and that is through the grounded conductor unless some other form of conductive material touches the exterior of the oven, such as a human.
The only explanation I can come up with is that the GFCI is expected to trip and open the circuit within about .03 seconds so this should be fast enough to protect the person.
