No GFI at RV refrigerator outlets?

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.
I repeat, GFCI's do not use a ground as shown in Tom's schematic. The two grounds shown are the outlet or device safety ground, and the neutral/ground connection at the primary panel. Take a look at a GFCI circuit breaker combo for another example. It only has one external white wire that's attached to the neutral bus, no ground connection.
 

Attachments

  • download.jpg
    download.jpg
    3.8 KB · Views: 0
It has already been invented. Every hair dryer and every GFI breaker has no ground wire and it has a test button. And here is a schematic and it is plain to see the test button does not use the ground.
I found the real two wire GFI with a test button. All complete. This schematic gives me a headache! I will look at it again later and see if I can figure out exactly how the test button works on a two wire GFI.

But I am glad you mentioned that as I didn't even realize I owned such until I checked my two wire hair dryer and it does have a GFI switch.

I wasn't sure if it was possible to have such a switch on a two wire, so I am glad to learn something here, even if it was right in front of my nose all the time!

-Don- Auburn, CA
 
GFCI's do not use a ground
Let's not confuse ground "wire" with ground "path".

We all know a ground wire is not needed for a GFI to trip. I have used one without a ground wire for many years when I lived in a house built in 1943 in South San Francisco. All two wire outlets. I added GFI to many of them. That was 20 years ago. Nothing new.

But how are you going to trip a GFI without a ground PATH? (please note I did not say "wire"). GFI protects you from a path to ground. That is what makes it trip! When there is a path to ground, say 30ma through your body, the gfi differential amplifier sees the 30 ma less on the white than is on the black wire and trips. The path for the 30 ma "lost" is through the ground back to the white wire. It arrives in an unexpected path at 30 ma so it trips and opens the black (I think some <all?> GFI adapters open the white as well--but what difference does that make, when the black is the only hot?).

GFI=Ground Fault Interrupter. They call it that for a reason. They named it correctly for what it does.

-Don- Auburn, CA
 
The schematic shows the same test button/resistor setup connected between the hot and neutral that Tom's schematic shows.
But his didn't show the opposite side of the test button. It went nowhere in Tom's schematic. Mine shows the entire circuit but what really confuses me in mine is what looks like two capacitors that they call the latch relay. I need more detail on mine as well, to really understand how that switch works.

Or perhaps somebody here can explain it. I am only interested in how the switch works to test on a two wire GFI. What make it interesting is there is only one possible path yet they find a way to test it.

But wait . . . .Does it really test a ground fault or does it only trip with that button? I am beginning to think it only trips. Not a true test of a ground fault. That would make perfect sense.

-Don- Auburn, CA
 
But his didn't show the opposite side of the test button. It went nowhere in Tom's schematic. Mine shows the entire circuit but what really confuses me in mine is what looks like two capacitors that they call the latch relay. I need more detail on mine as well, to really understand how that switch works.

Or perhaps somebody here can explain it. I am only interested in how the switch works to test on a two wire GFI. What make it interesting is there is only one possible path yet they find a way to test it.

But wait . . . .Does it really test a ground fault or does it only trip with that button? I am beginning to think it only trips. Not a true test of a ground fault. That would make perfect sense.

-Don- Auburn, CA
Click on Tom's thumbnail to see the whole drawing. I'll save you the trouble below. The test button connects a resistor between the hot and neutral that passes a small > 5mA current that's detected by the current transformer, opening the switching contacts.

GFI.jpg
 
Click on Tom's thumbnail to see the whole drawing. I'll save you the trouble below. The test button connects a resistor between the hot and neutral that passes a small > 5mA current that's detected by the current transformer, opening the switching contacts.
Thanks, yeah, I didn't realize the thumbnails were truncated until they are opened.

But do you see the obvious error in the schematic?

What it clearly shows is a resistor in series with a switch, going across the 120 VAC line as if it is a normal load. See the problem? It is the same as me putting a resistor across the same AC line. That resistor could be a normal load and it will not trip GFI.

What will happen if I put my own resistor of the same value across the same ac line? Absolutely nothing at all. Just a normal but extra light load. Putting a switch in series does nothing but take the small load off and on. That shouldn't trip any GFI.

I see they show a three wire outlet. The resistor should be going to the grounded green, not the white, then the outlet can see the incorrect path and trip when the button is pressed.

Or please explain this:

Let's say that resistor is 20KΩ. How does it tell the difference, in the schematic above, when the test button is pressed, when compared to my own 20KΩ load across the same AC line? Make the value anything you want, it will be the same difference.

IOW, just another load. The schematic needs a correction or needs to be clarified MUCH better than it is as shown.

-Don- Auburn, CA
 
What you're missing is only one leg of the test resistor load is inside the current detector loop.
Actually I did notice that, but I couldn't be sure if it was more than just the way it was drawn. IMO, if that is part of what is being sensed they should have used a different symbol than for a straight piece of wire as it goes through the transformer that detects the differential current. Or at least put a note there for clarification.

73, -Don- AA6GA
 
what really confuses me in mine is what looks like two capacitors that they call the latch relay.
Those aren't capacitors, they are the contacts of the relay. That's an industrial type of schematic representation of relay or contactor contacts.

As long as there is no ground fault the line and neutral wires will have equal and opposite currents and the current transformer will have 0V output. When you press the switch an extra 5-6mA flows through the transformer and unbalances it to the point where a voltage is induced and it trips.

If both lines of the test switch resistor were passed through the transformer it would be the same as a resistor plugged into the outlet but since only one leg of the circuit goes through the transformer it can be used to test.
 
Those aren't capacitors, they are the contacts of the relay.
Yeah, I know because of the "latching relay" label (link in message 22 here). But I am not used to seeing a relay look like that in a schematic. Here is what I would expect.

When you press the switch an extra 5-6mA flows through the transformer and unbalances it to the point where a voltage is induced and it trips.
Yeah, I can now see how it works--kinda. But that resistor lead that goes through the coil, what is it in reality? I doubt if it is only a resistor lead. I would like to see the actual guts in that area.

-Don- Auburn, CA
 
They absolutely react to current, b
I think you missed my point about semantics. A device can react to a condition without directly measuring sensing it. Thus a GFCI reacts to a short to ground (ground fault) whether the circuit has a ground wire or not, and without any physical connection to ground. Likewise, circuit breakers react to thermal and magnetic conditions that indicate an amp overload is occurring. It's academic whether the device is directly sensing/measuring or deriving a conclusion from associated conditions.
 
Yeah, I know because of the "latching relay" label (link in message 22 here). But I am not used to seeing a relay look like that in a schematic. Here is what I would expect.


Yeah, I can now see how it works--kinda. But that resistor lead that goes through the coil, what is it in reality? I doubt if it is only a resistor lead. I would like to see the actual guts in that area.

-Don- Auburn, CA

It's exactly what it looks like, the wire from one end of the resistor passes through the current sense loop along with the hot and neutral lines. When the button is pressed the small current in the resistor lead "fools" the sense circuit into seeing an imbalance greater than 5mA, causing the contacts to trip open.
 
It's important to note that the test condition actually adds current to the transformer to make the relay trip. there is no ground fault or ground path involved. A lightning strike, hitting a power pole or even a faulty generator could all, also, unbalance the line and cause the contacts to open. The GFCI does'nt care if some is leaking out or if more is being added in, a more appropriate name would have been "Balanced line circuit protection"

Last summer I installed an air conditioner on our house. Since it sits outside I assumed it needed a GFCI breaker to service it. Bad assumption. Once up and running the breaker would trip four or five times a day for no apparent reason. After a little research I found out that a GFCI breaker is not required on an AC unit and that the compressor itself was causing the false trips by sending back EMF through the breaker on startup which would unbalance the line and cause the GFCI to open the contacts. I installed a regular breaker and now all is well. (I should have read the manufactures manual more thoroughly!).

Most RV refrigerators don't have compressors but some do, maybe that's the reason for not requiring GFCI on outlets that are "inaccessible".

JayArr
 
Since it sits outside I assumed it needed a GFCI breaker to service it. Bad assumption. Once up and running the breaker would trip four or five times a day for no apparent reason.
I wonder if it would be okay with the older, less sensitive GFI's. As I mentioned here before, IMO, 5ma is too sensitive and I doubt if 20ma for such a short time through a human body is a problem. People will probably feel the 20 ma, unlike the 5ma that most people often don't even feel, yet can cause the GFI trip, but I doubt there is a real safety issue with allowing 20 ma. But OTOH, I wonder why they were changed to 5 ma.

Most RV refrigerators don't have compressors but some do, maybe that's the reason for not requiring GFCI on outlets that are "inaccessible".

I found another outlet in my RV that has no GFI. Even more inaccessible than the refrigerator outlet. That is the outlet for my converter. Another single outlet, just like the one to my refrigerator. There, I see no need at all for GFI.

-Don- Auburn, CA
 
there is no ground fault or ground path involved.
That was why I doubted if it were possible to have a test switch. But they do, by fooling a circuit, not a true ground fault test as such is not possible on two wires, but it does work much the same way by creating and detecting its own imbalance. It's the best test possible when only two wires are available (no possible third path available until there is a REAL ground fault).

What really surprises me is I own two 2-wire hair dryers here with such a switch but I never even noticed their GFI switches until this thread.

These days, the hair dryer GFI switch, as well as the entire hair dryer GFI is redundant and unnecessary except in older homes that have no bathroom GFI. OTOH, perhaps some dry their hair at another location, such as the living room which has no GFI. But it is hard to find anything grounded in a living room anyway, so a ground fault there isn't normally possible anyway.

-Don- Auburn, CA
 
It's important to note that the test condition actually adds current to the transformer to make the relay trip. there is no ground fault or ground path involved. A lightning strike, hitting a power pole or even a faulty generator could all, also, unbalance the line and cause the contacts to open. The GFCI does'nt care if some is leaking out or if more is being added in, a more appropriate name would have been "Balanced line circuit protection"

Last summer I installed an air conditioner on our house. Since it sits outside I assumed it needed a GFCI breaker to service it. Bad assumption. Once up and running the breaker would trip four or five times a day for no apparent reason. After a little research I found out that a GFCI breaker is not required on an AC unit and that the compressor itself was causing the false trips by sending back EMF through the breaker on startup which would unbalance the line and cause the GFCI to open the contacts. I installed a regular breaker and now all is well. (I should have read the manufactures manual more thoroughly!).

Most RV refrigerators don't have compressors but some do, maybe that's the reason for not requiring GFCI on outlets that are "inaccessible".

JayArr
One of the more recent editions of the NEC does now require GFIs on appliance outlets. Even the ones behind the refrigerator. Of course, they don’t require retrofitting but for new construction, a dead front gfi is used to the normal outlet with the dead front being installed in an accessible location.

Back in 2008 when I renovated, the code did not require GFIs on dedicated outlets, for example, the one powering my sewage pump in basement floor, the refrigerator or freezer.
 
One of the more recent editions of the NEC does now require GFIs on appliance outlets. Even the ones behind the refrigerator. Of course, they don’t require retrofitting but for new construction, a dead front gfi is used to the normal outlet with the dead front being installed in an accessible location.

Back in 2008 when I renovated, the code did not require GFIs on dedicated outlets, for example, the one powering my sewage pump in basement floor, the refrigerator or freezer.
Section 210.8(A)(6) of the 2020 NEC only requires GFCI protection in dwelling unit kitchens "where the receptacles are installed to serve the countertop surfaces." Section 210.8(A)(7) also requires GFCI protection for any receptacles with 6 ft of a sink, so I suppose that could apply in some kitchen refrigerator receptacle situations.
 
Back
Top Bottom