Which is what I wanted. This GFCI is installed inside (where no GFCI protection is needed) and it controls an outside light. The GFCI acts as a light switch (at least it used to, before I had to replace it with one of those "improved" ones).
In alt.engineering.electrical Bud-- wrote: | Mark Lloyd wrote: |> On Fri, 29 Sep 2006 11:00:11 -0500, Bud-- |> wrote: |> |> [snip] |> |> |>>GFCIs (5mA) are now required to not work with reverse load-line terminal |>>wiring. |> |> |> Even when that's exactly what you want. |> | | When the supply wires are connected to the LOAD terminals on old GFCIs, | the GFCI receptacle is not protected - it is live even if the GFCI is | tripped. (I believe the downstream circuit, which would be connected to | the LINE terminals, is protected.) | | Under the new UL standard, which I think was adopted about 2 years ago, | if you connect supply wires to the LOAD terminals the GFCI receptacle | and LOAD terminals will always be dead. | | I may have tried to say that with too few words.
Someone once told me that the GFCI receptacles that I found were DANGEROUSLY susceptible to strong radio fields, must have been wired in reverse. But I do know they did cut off the power to its own outlets, so I am convinced that they were wired correctly. Maybe they are defective products and the internal solenoid that trips the mechanism was wired on the LINE side and should have been wired on the LOAD side.
What happens is that when a strong radio field is introduced, the GFCI sees this somehow as leakage current. Other than for it being the wrong frequency this is understandable, as the induced currents would be in common mode, with the same direction on hot and neutral.
The DANGEROUS part is that even though the solenoid has opened the circuit and cut off the power from the outlets (and presumably upstream, which was not present for the ones I did this with), as long as the radio current was present, the solenoid continued to activate. I believe that these solenoids would be operating from the 120 volts AND are not designed for the heat that would result from continuous operation. They would have been designed with the idea in mind that as soon as the circuit opened, the leakage current would no longer be present.
This creates TWO hazard conditions.
The first is that if a radio field that caused this was external, it might not be known to the radio operator that there was a problem. It could cause the solenoid to overheat, melt insulation, short circuit, arc, catch fire, burn the house down, and KILL PEOPLE. I did NOT leave the radio field on for a long period of time when I did this test. Even for the very first time I discovered this, the loud buzzing of the solenoid in the GFCI was loud enough to get my quick attention and realize the radio was triggering the problem. So I was never doing this for more than a second or two.
The second hazard exists if the GFCI breaker does NOT open the neutral. A neutral could have some low voltages present as a result of voltage drop between various L-N 120 volt loads and the point of bonding neutral to ground. A short circuit from neutral to ground might not have a great spectacular arc flash, but it could draw enough current to activate a GFCI at the 5ma level. The type of GFCI that allowed the radio current to trip the solenoid continuously would also result in continuous activation of the solenoid in this neutral-only leakage situation because the neutral would not be opened, and the GFCI control circuitry would still be powered.
I believe a proper GFCI design must cut off its own power when tripped, so it is not doing a continuous trip. This could be done by powering the GFCI control circuitry, including the solenoid, from the LOAD side. When I suggested this in a posting somewhere a long time ago, someone said that it may be needed to power the solenoid from the LINE side to ensure that it completes its operation to full open the contacts. I can agree that leaving the contacts stuck in a partial open state where they may arc across is not a good thing. But this should be accomplished through the mechanical energy stored in the unfatiguable spring mechanism that gets charged when the unit is reset. The solenoid should just be releasing that spring.
DO NOT DO THIS AT HOME OR WORK. There is the risk that some of these units may be so defective that even a short period of operation could result in substantial damage.
I also do not know if GFCI breakers have this risk. If their internal circuitry remains energized from the bus contacts in the panel, a radio field could cause the very same problem. Although they clearly do have the proper spring loading mechanism, being a part of a circuit breaker, the solenoid that releases that mechanism when leakage current is detected would potentially be under continuous operation if the power remains and the apparent leakage issue remains. This would not only be a problem with a continuous radio field, but it could also be a problem when the neutral has enough voltage to make a leak to ground, such as in a subpanel. So DO NOT DO THIS NEAR A BREAKER PANEL.
The grounding conductor is irrelevant to GFCI operation. Both the neutral and the hot are interrupted when a GFCI receptacle trips.
It uses a special transformer to measure the current on the
You have the above mis-identified. The neutral *is* the groundED conductor. The UNgrounded conductor is (a.k.a. "hot") NOT the white conductor, unless the circuit is miswired. The white can be re-identified as black with black tape or equivalent and then used as a hot wire.
The difference is that the neutral (groundED) wire carries current, under normal circumstances. The groundING wire does not. It takes two faults to shock/hurt/kill you if you are in contact with the grounding wire; it takes one fault to shock/hurt/kill you if you are in contact with the neutral wire.
Ed
In alt.engineering.electrical ehsjr wrote: | PPS wrote: |>>I have been told, but have never sacrificed a device to verify, or set up |>>the appropriate test, that GFCI receptacles open BOTH the hot wire AND the |>>neutral wire when they trip. If so, why is that? Is it to offer at least |>>some protection even when the device is miswired? Or is there even some |>>risk with voltages on the neutral wire? |> |> |> Just opens the ungrounded conductor, not the ground (mistakenly called a |> neutral). | | | The grounding conductor is irrelevant to GFCI operation. | Both the neutral and the hot are interrupted when | a GFCI receptacle trips.
So why is the neutral opened? That's an "academic question" (I can come up with what I think are good reasons to do so). Now, considering answers to this question, what protections might be lost if AFCI breakers that include GFCI protection at the 5ma level result in GFCI receptacles not being used? Is GFCI protection in a breaker considered adequate for the requirements in NEC 210.8 even though it does not open the neutral connection? Would YOU persoanlly feel less safe if all the receptacles in a kitchen were protected for ground fault leakage only by circuit breakers at the panel (assume that the panel is close by).
There must be _some_ reason _they_ chose to include opening the neutral in GFCI receptacles (maybe more than one). But wouldn't such reasons also be applicable to circuit breaker based protection?
What if you have _both_ GFCI protection at the breaker _and_ GFCI protection at the receptacle, say in a bathroom. Now suppose there is a slight leakage fault, but only the breaker opens on it. Maybe the receptacle was going to interrupt the fault, but was just sufficiently slow, perhaps due to a slow rise in the leakage current, that the breaker did it first, which prevents the receptacle from doing so. Now you have a condition where the neutral continues to be fully connected all the way from the main panel, through the GFCI receptacle that no longer has power on it's hot wire, and into the plugged in appliance that someone grabbed with a dripping wet hand while also grabbing a towel out of the basin water in the sink.
Well, usually, a neutral doesn't have much voltage relative to ground. But if there was some kind of open neutral condition also present (now we are at the level of _two_ existant problems) and a rather unbalanced load between the two single phase poles (somewhat common), we could be dealing quite many volts still available through the GFCI receptacle that didn't trip because it lost power due to the ground fault that was detected by the breaker first.
So my thinking here is, if there is protection to be gained by opening the neutral at GFCI receptacles, we should _not_ be requiring that AFCI breakers be of the type that combine GFCI protection. And perhaps such breakers should be prohibited for these circuits.
Of course there is also the issue of the inconvenience of going all the way to the breaker panel to reset a ground fault. This could be particularly so for bathrooms (imagine being dripping wet, wearing only a towel, going out to the garage or down to the basement, standing on a concrete floor, to reset a breaker).
What makes you so certain that a GFCI circuit breaker does not open the neutral? Have you checked with several manufacturers.
One reason why it might be OK for a breaker to leave the neutral alone is that it is far less likely and in fact rather difficult for a breaker to be revere wired. When a breaker type GFCI operates it will nearly always open the ungrounded conductor. There are a lot more ways a receptacle type of GFCI can be supplied with the ungrounded conductor controlled by the grounded conductor leg of the GFCI mechanism.
| What makes you so certain that a GFCI circuit breaker does not open the | neutral? Have you checked with several manufacturers.
I've looked at the engineering diagrams, cut-aways, and schematics. There are no contacts for interrupting the neutral wire.
| One reason why it might be OK for a breaker to leave the neutral alone | is that it is far less likely and in fact rather difficult for a breaker | to be revere wired. When a breaker type GFCI operates it will nearly | always open the ungrounded conductor. There are a lot more ways a | receptacle type of GFCI can be supplied with the ungrounded conductor | controlled by the grounded conductor leg of the GFCI mechanism.
So basically, there is no goal or interest in specifically opening the neutral. It's just a case of opening both in situations where either might be the neutral.
A "neutral" is not defined in the NEC, but is described in Article
310.15(B)(4) as carrying "only the unbalanced current from other conductors...".In a 120 volt (lighting) circuit, the current is carried on both the white (or "grounded") conductor and an "ungrounded (usually black, but not necessarily) conductor. The term "neutral" refers to the neutral connection at the transformer; the center-tap. In a pure 240 volt circuit, current flows on the two phase conductors and a white (or grounded) conductor in not even needed. By introducing 120 volt circuits, the white forms one of the return legs, and carries current. (240 v between the ungrounded legs, 120 v from either leg to the neutral.)
In Europe, the term "neutral" does include a grounded conductor in a 120 v circuit. In the states the term is used interchangeably but in error.
| A "neutral" is not defined in the NEC, but is described in Article | 310.15(B)(4) as carrying "only the unbalanced current from other | conductors...".
"Neutral conductor" is defined in the NEC. The term is used in many places. I fully understand what a neutral is. Are you raising an issue about its common or formal usage?
| In a 120 volt (lighting) circuit, the current is carried on both the white | (or "grounded") conductor and an "ungrounded (usually black, but not | necessarily) conductor.
If you are wanting to get very specific, it's the insulators that have the color. The current is carried on the (usually) copper metal (with a magnetic field, of course).
The code requires the grounded conductor be identified well (e.g. continuous color, not just marked at each end). Others have more leeway.
| The term "neutral" refers to the neutral connection at the transformer; the | center-tap. In a pure 240 volt circuit, current flows on the two phase | conductors and a white (or grounded) conductor in not even needed. By | introducing 120 volt circuits, the white forms one of the return legs, and | carries current. (240 v between the ungrounded legs, 120 v from either leg | to the neutral.)
You could tap the transformer off-center a bit if you wanted to and have
115 volts on one side and 125 volts on the other side. Would you call that a "neutral"?So tell me ... what happens if you have a couple of very low power factor loads, one on each 120 volt side, where one is very inductive and the other is very capacitive? Now how much current flows on the "neutral"?
| In Europe, the term "neutral" does include a grounded conductor in a 120 v | circuit. In the states the term is used interchangeably but in error.
I see very little use in error in the US. Neutral does not mean grounded, but it generally implies that because that is the required way to wire it up. See NEC 250.26(2). The two terms "neutral conductor" and "grounded conductor" do have different meanings, but are associated with the same wire because that is the required way.
Single phase in Europe is generally 2-wire service. You can still call one wire neutral because it may well be the wire connected to the real neutral point in either a single phase transformer (center tapped 230/460) or a three phase transformer (connected to the star common). But it is grounded and thus (also) correct to call it a grounded conductor. If the service is coming from a 2-wire transformer all by itself, then it's not really neutral; it's just grounded.
In Europe, there are no 120V circuits, and "neutral" is a supply current carrying conductor which is at or near ground potential.
In alt.engineering.electrical Andrew Gabriel wrote: | In article , | "PPS" writes: |> In Europe, the term "neutral" does include a grounded conductor in a 120 v |> circuit. In the states the term is used interchangeably but in error. | | In Europe, there are no 120V circuits, and "neutral" is a supply | current carrying conductor which is at or near ground potential.
But that doesn't really change the meaning's origin. The first power systems were three phase to drive motors. I don't know if delta was used much way back when, but with star/wye configurations, you do have a genuine neutral. When single phase at 240v is taken from that, the neutral is still there. It just doesn't have enough phases brought in to take the neutralizing role there.
The neutral role is still there, i.e. it's still at or near ground potential.
Now there are some single phase supplies in europe which don't have a neutral, but they are much less common and only in a few countries (not UK). An example is a single phase supply from a corner grounded delta, where both of the lines are taken from a non-grounded corner.
There are also IT supplies which are isolated with just a resistance to ground to prevent the secondary capacitively floating up to the much higer primary voltage. Strictly the side with the resistor to ground is still called a neutral, although it might be some way from ground potential. Again, I believe some parts of Europe use this, but it only occurs in the UK on standalone generators, not from the public supply.
In alt.engineering.electrical Andrew Gabriel wrote: | In article , | snipped-for-privacy@ipal.net writes: |> In alt.engineering.electrical Andrew Gabriel wrote: |>| In article , |>| "PPS" writes: |>|> In Europe, the term "neutral" does include a grounded conductor in a 120 v |>|> circuit. In the states the term is used interchangeably but in error. |>| |>| In Europe, there are no 120V circuits, and "neutral" is a supply |>| current carrying conductor which is at or near ground potential. |> |> But that doesn't really change the meaning's origin. The first power |> systems were three phase to drive motors. I don't know if delta was |> used much way back when, but with star/wye configurations, you do have |> a genuine neutral. When single phase at 240v is taken from that, the |> neutral is still there. It just doesn't have enough phases brought |> in to take the neutralizing role there. | | The neutral role is still there, i.e. it's still at or near ground | potential.
But that's not what the meaning of neutral is. It's neutral whether it is grounded or not. In cases where there are 2 or mroe phases, the idea is that when things are in balance, there is no current on the neutral. It was neutralized by the balance. But I think the meaning really comes from the neutral point in the transformer winding of the secondary.
| Now there are some single phase supplies in europe which don't have | a neutral, but they are much less common and only in a few countries | (not UK). An example is a single phase supply from a corner grounded | delta, where both of the lines are taken from a non-grounded corner.
Apparently these are older connections. From what I gather, the first power in much of Europe in the late 1800's was 220/127 three phase. It appears that predated Edison supplying light to New York, so it seems he took the 220 voltage and split it for DC. He likely also realized, in all his light bulb work, that a lower voltage worked better on the filament. I've heard that the 220/127 can still be found in some remote locations like way north Norway and rural parts of Spain. A friend has reported seeing the remnants of 220/127 wiring in buildings in Germany predating WW1.
| There are also IT supplies which are isolated with just a resistance | to ground to prevent the secondary capacitively floating up to the | much higer primary voltage. Strictly the side with the resistor to | ground is still called a neutral, although it might be some way from | ground potential. Again, I believe some parts of Europe use this, | but it only occurs in the UK on standalone generators, not from the | public supply.
The reason they use that resistance instead of a solid ground is to avoid single fault failures. But during that time, one hot line is now grounded.
It is more likely that the rf is getting into the GFCI electronics directly, rather than through the toroid. I suspect the input to the chip is fairly high impedance, and there may even be some non-linearity that acts as a detector.
I know you have mentioned this before, and although I have never experienced it, I can easily believe that it can happen. I might try some experiments to replicate it. Do you have any idea of how strong and at what frequency the rf was?
Ben Miller
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