GFCIs and EGCs

[mbrooke]

It's ok to play devils advocate to expand your knowledge - I do the same sometimes. Sometimes a reason for the question can narrow down an interpretation that can be accepted or fuel for rebuttal. I know from 1st hand experience no one walks on egg shells when it comes to answers.

I guess my question is why don't all metal frame appliances come with 3 prongs?

My theory is that if all kitchen appliances had 3 prongs, GFCIs would only be required where an EGC can no longer provide safety, such as immersion (and broken ground pin is a valid argument). In terms of immersion an EGC would actually provide increased safety, where as a 2 prong appliance may not trip a GFCI if a pool, sink or tub was ungrounded. A 3 prong appliance plugged into a GFCI circuit is in essence an LCID, which provides the ultimate protection.

 

[mbrooke]

I tend to see this as part of the historical progression of increasing "safety" to attempt to prevent fewer and fewer harmful events.

1. Ground the generator frame.
2. Connect the Premises Wiring (System) to the metallic water piping system.
3. Require Equipment Grounding Conductor (EGC).
4. Require Ground Fault Circuit Interruption.
5. Require Arc Fault Circuit Interruption.

At this point, in the early 21st Century, we are chasing fewer and fewer harmful events with more and more requirements.

When considering changing a two wire ungrounded appliance to an appliance with an EGC, one is extending the level a safety in #3 above, so one is technically increasing the safety at the appliance.

However, GFCI has, historically, been required to be added to branch circuits (in new construction) that already have EGCs present. . . that is, the GFCI is added to the EGC because even more safety for personnel is achieved.

Whether the EGC extends from the branch circuit to the utilization equipment, or not, doesn't really affect the overall increase of safety for personnel that comes only with the addition of the GFCI to the outlet, IMO.

I disagree. A GFCI is hit or miss when the appliance is 2 prong. If I drop a 2 prong appliance plugged into a GFCI into a non grounded tub or pool the GFCI would not trip. It would produce voltage gradients, often enough to harm, but the GFCI would sense no imbalance. So in terms if providing safety around water, GFCI are somewhat misleading. Now, if an EGC was present current would have a place to return via a path that does not go through the GFCI which would read as an imbalance and trip.

 

[mbrooke]

How would you do that? How would a device at the panel know the difference between a series glowing fault in the wiring of a branch circuit and a toaster plugged into an outlet on that circuit?

1. fall of potential

or

2. Thermal fusing connections



In 2015 I refuse to believe that no one has thought of something. In fact Cutler hammer (among others)already has:


https://www.google.com/patents/WO20...&sa=X&ei=XdcuVeDpIcmVNuu7gIAE&ved=0CB0Q6AEwAA


https://www.google.com/patents/US88...&sa=X&ei=XdcuVeDpIcmVNuu7gIAE&ved=0CCQQ6AEwAQ

 

[mbrooke]

Absolutely! A GFCI does not require an EGC to operate. The NEC started requiring EGCs in the mid 60s' but we still saw in increase in shocks and deaths.
Even with a EGC, a 20 amp breaker on a line to case fault, won't trip at 20 amps, or even 25 amps.
GFCIs are a proven life saving device.

True, but how many appliances took the EGC from the wall? I can still buy metal frame appliances with no EGC. Further, a GFCI without an EGC has limitations where no ground path exists such as an insulated tub, pool or sink.

 

[fmtjfw]

True, but how many appliances took the EGC from the wall? I can still buy metal frame appliances with no EGC. Further, a GFCI without an EGC has limitations where no ground path exists such as an insulated tub, pool or sink.

Metal framed toasters, by design, do not have grounded cases. They have exposed conductors (the heating elements). They are normally plugged into GFCI protected receptacles. That way if you stick a metal fork or knife into them to prise out a piece of toast, when you contact a uninsulated conductor you trip the GFCI rather than blowing off the tip of the utensil.

GFCI's are really current imbalance detectors. Many of the imbalances they detect are to ground, but that is not necessary. If you touch the phase-A hot wire protected by a GFCI and then also touch the phase-B hot wire, a single-pole GFCI will trip, no ground involved.

 

[don_resqcapt19]

... Further, a GFCI without an EGC has limitations where no ground path exists such as an insulated tub, pool or sink.

Are you talking about a two wire device in water that is in an non-conductive container? If so, that can set up dangerous voltage gradients in the water without the GFCI tripping...in fact that type of situation is the very reason that Article 680 requires the pool water to be bonded.

 

[al hildenbrand]

I disagree. A GFCI is hit or miss when the appliance is 2 prong. If I drop a 2 prong appliance plugged into a GFCI into a non grounded tub or pool the GFCI would not trip. It would produce voltage gradients, often enough to harm, but the GFCI would sense no imbalance. So in terms if providing safety around water, GFCI are somewhat misleading. Now, if an EGC was present current would have a place to return via a path that does not go through the GFCI which would read as an imbalance and trip.

Your scenario makes no sense to me. In stating that the tub or pool is "non grounded" there is no ground plane, therefore there is no fall-of-potential, i.e., there is no voltage gradient, and, certainly, no current flow.

 

[al hildenbrand]

Your scenario makes no sense to me. In stating that the tub or pool is "non grounded" there is no ground plane, therefore there is no fall-of-potential, i.e., there is no voltage gradient, and, certainly, no current flow.

More importantly, the GFI never protects people in Line to Neutral faults where the person's body is in the circuit path between the Line and the Neutral. You are stating a "normal" condition.

People will still be able to not touch the EGC and connected conductive materials until you require bonding the EGC to a person.

 

[mbrooke]

Are you talking about a two wire device in water that is in an non-conductive container? If so, that can set up dangerous voltage gradients in the water without the GFCI tripping...in fact that type of situation is the very reason that Article 680 requires the pool water to be bonded.

That's my exact point, if an EGC existed than a GFCI is practically an LCID. But you are correct, bonded pools will trip. However, inflatable pools are another story. Who bonds those?

 

[mbrooke]

Metal framed toasters, by design, do not have grounded cases. They have exposed conductors (the heating elements). They are normally plugged into GFCI protected receptacles. That way if you stick a metal fork or knife into them to prise out a piece of toast, when you contact a uninsulated conductor you trip the GFCI rather than blowing off the tip of the utensil.

GFCI's are really current imbalance detectors. Many of the imbalances they detect are to ground, but that is not necessary. If you touch the phase-A hot wire protected by a GFCI and then also touch the phase-B hot wire, a single-pole GFCI will trip, no ground involved.

But, if the element touched the frame, it would electrify. Thus this was probably what drove GFCI past 6 feet of the sink. As for unintentionally not bonding (grounding) the toaster, is there anything that backs this up?

 

[mbrooke]

Your scenario makes no sense to me. In stating that the tub or pool is "non grounded" there is no ground plane, therefore there is no fall-of-potential, i.e., there is no voltage gradient, and, certainly, no current flow.

There is no other path back to the source be it EGC or soil. In such a case no imbalance would present itself to a GFCI thus it will never trip.


However, a voltage gradient will form across the water, and ironically the absence of an EGC will not give some of it a return path to trip the GFCI.

 

[al hildenbrand]

There is no other path back to the source be it EGC or soil. In such a case no imbalance would present itself to a GFCI thus it will never trip.

First, I totally get that a GFCI will only react to an imbalance of current between the line and the neutral within the GFCI sensor. AND I totally get that a line thru human to neutral fault on the load side of a GFCI will NOT result in an imbalance of line and neutral current at the GFCI sensor.

Your example of the two wire (without EGC) appliance creating a human hazard of voltage gradients in an ungrounded tub or pool, when coupled with your OP goal of DECREASING the requirements for installing GFCIs makes no sense to me. Adding the EGC to the tub or pool does not allow the decrease of hazard from voltage gradients in the water in the tub or pool if you DON'T have a GFCI.

If all metal cased appliances were mandated by UL and the NEC requiring a 3 prong plug, would GFCI requirements still be as necessary in some places?

Your tub or pool scenario only helps to ensure the continued requirement for GFCI in the tub or pool scenario.

 

[mbrooke]

First, I totally get that a GFCI will only react to an imbalance of current between the line and the neutral within the GFCI sensor. AND I totally get that a line thru human to neutral fault on the load side of a GFCI will NOT result in an imbalance of line and neutral current at the GFCI sensor.

Your example of the two wire (without EGC) appliance creating a human hazard of voltage gradients in an ungrounded tub or pool, when coupled with your OP goal of DECREASING the requirements for installing GFCIs makes no sense to me. Adding the EGC to the tub or pool does not allow the decrease of hazard from voltage gradients in the water in the tub or pool if you DON'T have a GFCI.

You are correct, however all this shows is the need for an EGC in addition to a GFCI.

But what about where a pool or sink isn't present? Why still require GFCI where no voltage gradient will form?

Your tub or pool scenario only helps to ensure the continued requirement for GFCI in the tub or pool scenario.

Yes, but not for places that go beyond a pool or sink.

 

[al hildenbrand]

. . . . not for places that go beyond a pool or sink.

Ok. What do you mean? Where does extending the EGC result in the lack of a need for a GFI in the situations currently required by the 2014 NEC?

 

[mbrooke]

Ok. What do you mean? Where does extending the EGC result in the lack of a need for a GFI in the situations currently required by the 2014 NEC?

Areas beyond 6 feet of a sink, unfinished basements, garages, laundry areas, and I am sure a left out a few.

 

[al hildenbrand]

Areas beyond 6 feet of a sink, unfinished basements, garages, laundry areas, and I am sure a left out a few.

How do you propose to handle the extensive quantity of existing UNgrounded utilization equipment and cord sets? Would you require the EGC extension beyond the reach of the NEC into manufactured hardware and then, after, say, fifty years, to allow the non-EGC apparatus to age out of existence, THEN relax the GFCI requirements?

 

[mbrooke]

How do you propose to handle the extensive quantity of existing UNgrounded utilization equipment and cord sets? Would you require the EGC extension beyond the reach of the NEC into manufactured hardware and then, after, say, fifty years, to allow the non-EGC apparatus to age out of existence, THEN relax the GFCI requirements?

I would get an EGC into all applainces. Even if GFCI requirments are not relaxed, this still provides enhanced safety in complete imersion. I would also have all double insulated applainces like hair dryers drop GFCI cord caps in favor of an LCID cord cap.

 

[kwired]

There are lots of things out there that have nothing conductive exposed to connect an EGC to which is part of reason they only have a two wire plug in the first place. Other items with conductive surfaces possibly have them sufficiently isolated so that it is nearly impossible to energize that surface (this is a qualification for double insulation systems). Right in front of me right now is my notebook computer- two wire cord to a power supply that is completely non metallic housed - what is the purpose of adding a EGC in that instance?

 

[mbrooke]

There are lots of things out there that have nothing conductive exposed to connect an EGC to which is part of reason they only have a two wire plug in the first place. Other items with conductive surfaces possibly have them sufficiently isolated so that it is nearly impossible to energize that surface (this is a qualification for double insulation systems). Right in front of me right now is my notebook computer- two wire cord to a power supply that is completely non metallic housed - what is the purpose of adding a EGC in that instance?

I know, but how many all metal frame appliances like toaster ovens and waffle makers still come with 2 prongs? Open one of those up, no safeguard exists to prevent a line to case fault, and no double insulation mark exists on the sticker.

Your laptop computer is a poor example, other than MOV surge suppression an EGC is useless, and it is unlikely the charger will be submerged in water. So in this case yes, an EGC serves no purpose.

As for double insulted items that could become submerged an EGC can help those, however it will add more cost (larger copper ground in the copper) when compared to an LCID cord cap.

 

[kwired]

I know, but how many all metal frame appliances like toaster ovens and waffle makers still come with 2 prongs? Open one of those up, no safeguard exists to prevent a line to case fault, and no double insulation mark exists on the sticker.

Your laptop computer is a poor example, other than MOV surge suppression an EGC is useless, and it is unlikely the charger will be submerged in water. So in this case yes, an EGC serves no purpose.

As for double insulted items that could become submerged an EGC can help those, however it will add more cost (larger copper ground in the copper) when compared to an LCID cord cap.

When my computer is on my desk in the office it(the power supply) is unlikely to be submerged, if I bring it to the kitchen that risk does increase - and is a major reason there is a GFCI in the kitchen and not the office.