Beware of your differential circuit breakers (GFCI)!

[Calambres]

This is a topic to warn you about failing differential circuit breakers in your homely electric installation.

We all (must) know that the test button in those switches is there to perform a monthly test to see if the circuit breaker is working. My word of advice is to distrust this procedure and go a bit further based upon my recent experience. I, like most of us, refrain to perform the monthly test and only do it once in a blue moon or simply when it comes to mind. The other day I was lurking youtube and found one talking about a simple differential switch tester (a Triac, a Diac, 4 resistors, 3 capacitors, a potentiometer, a SDPT switch and a 50mA AC analog panel)  with which you can test not only if it works but "when" it works, I mean, how many mA are needed to trip the typical 30mA differential switch we all have at home for our security.

The fact was that I had a couple of "Very Expensive Super Immunized 30mA Differential Switches With Automatic Reconnection" at home from a "Very Reputable Brand", both installed on independent branches of the electrical grid at home and with no more than 4 years of use. Both of them pass the test button test OK but one didn't work at all as a differential switch    The one in my house tripped the switch at 25mA (very common for a 30mA breaker) and auto reconnected like a charm but the other in my "den"  didn't trip at all, not even at 50mA... although, as I said before, it passed the button test perfectly . This is the one responsible of protecting my work bench where I do all things electric and electronic, my garage and my mechanical shop 

My word of warning is to be aware that the "monthly test button test" may not be definitive and your safety may be in danger: Place a load of between 15mA to 30mA between the live and earth and see if the differential switch go down.

Sorry if this is not the correct place to put this thread. Feel free to move it to a better place if necessary.

[EDIT] I'm talking about a GFCI Breaker or Ground Fault Circuit Interrupter.

[TK]

I guess you mean A and not mA

[Dubbie]

No, this is not a over current circuit breaker, it is a ground leakage detector.

Basically it checks to see that the same current is flowing “out” through the phase as is coming “back” through the neutral. If there is a discrepancy, it means there is some fault that is letting current leak to ground. Maybe a finger in a light socket somewhere, or a drywall screw through some tps cable? There is a threshold of a few tens of mA so that ordinary inductive and insulative leakage doesn’t trip it constantly for no real fault.

Of course if your finger forms part of a circuit between phase and neutral, the power will still return through neutral and the thing won’t trip.

I suspect TK knows this already, so is more for benefit of others who may not.

[Monkeh]

I guess you mean A and not mA

No. No, he really doesn't.

[CatalinaWOW]

I guess you mean A and not mA

Very possible that you needed some coffee before making this comment.  If something like that was not the problem I would suggest staying far from hardware, and be cautious what you suggest others do in your systems analysis role.

I will also give you an out on language problems.  Here in the US these breakers are called GFI or GFCI breakers.  This forum is often widely separated by a common language.

[tautech]

If your den is on a submain distribution board your mains ground return path could be suspect.
Try checking den mains ground to a local earth and see if there's a voltage differential. If any it should be very low.

[TK]

(very common for a 30mA breaker)

What about here?  Is it 30A breaker (GFI) or 30mA?

I must admit it was not lack of coffee.  I know my limitations and I would never give any recommendation regarding anything related to mains or electric wiring or safety.  I still consider to be a total ignorant on this field... I was one of the ignorants that connected the ground clip of a Rigol scope to the 110V section of a power supply (Live / Neutral) and experienced a huge spark, the scope survived but took years to understand why it went wrong.

I know what a GFI is, but did not know how it operates... I learned something new today

[TK]

I suspect TK knows this already, so is more for benefit of others who may not.

I didn't know

[woody]

I always wonder if there are many people that test these things once a month.
Nowadays that means first shutting down pc's, a couple of NASes, the heating, the alarm system, a mail server, the router, and then run a real risk that one of the many, many connected SMTPs does not come back up after the test.
Who makes time for that 12 times a year?

[james_s]

I probably test my GFCI breakers once a year if that. Never in my life have I encountered one that failed to trip. I did have to replace one at my mom's place recently that would trip immediately with nothing plugged in. Replacing the GFCI cured the problem.

[Monkeh]

I probably test my GFCI breakers once a year if that. Never in my life have I encountered one that failed to trip. I did have to replace one at my mom's place recently that would trip immediately with nothing plugged in. Replacing the GFCI cured the problem.

You've never encountered one which fails to trip at the massively excessive current applied by the test button. How many times (if ever, since leaving the factory..) have any of those breakers actually had their trip characteristics verified?

[Gyro]

I probably test my GFCI breakers once a year if that. Never in my life have I encountered one that failed to trip. I did have to replace one at my mom's place recently that would trip immediately with nothing plugged in. Replacing the GFCI cured the problem.

I have. Admittedly it was a fairly old one but having experienced it, I now have that slightly uncomfortable feeling having just tested it, will it fail to trip next time?  It can lead to compulsive button pressing syndrome.

[Dwaine]

Instead of going with GFCI breakers in my home.  I just went to better plugs.  Some nice Hospital Grade plugs with filtering and Audio Alarm.

[Monkeh]

Instead of going with GFCI breakers in my home.  I just went to better plugs.  Some nice Hospital Grade plugs with filtering and Audio Alarm.

And how is a 'plug' (you'll find that's a socket) a replacement for a protective circuit?

[steverino]

I think the newer GFCI devices (outlets and breakers) are required to self test, at least in North America (UL943 2015).  Here's a common chip used in newer leviton gfci outlets (at least i think this is the chip used, the markings on the chip were removed).

http://www.onsemi.com/PowerSolutions/product.do?id=FAN4149

[Calambres]

If your den is on a submain distribution board your mains ground return path could be suspect.

That's the first thing I thought but it is not so. I replaced the failing switch with a new one and this works perfectly and trips at 22mA. Besides, I checked the ground path as well as the isolation from live to earth with a megger. All was OK.

Regarding the discussion about A vs. mA I think the problem is in the nomenclature. I'm not used to your namings because english is not my mother language. Of course I meant CFGI breakers. It was a 40A and 30mA sensitivity CFGI.

And yes, I'm afraid that the test button is not enough indication that the thing is working properly and hence my warning.

[tautech]

If your den is on a submain distribution board your mains ground return path could be suspect.

That's the first thing I thought but it is not so. I replaced the failing switch with a new one and this works perfectly and trips at 22mA. Besides, I checked the ground path as well as the isolation from live to earth with a megger. All was OK.

Great, then it was a dud breaker.
Was it checked as OK at initial installation ?

[Calambres]

Of course if your finger forms part of a circuit between phase and neutral, the power will still return through neutral and the thing won’t trip.

AFAIK, in Europe the neutral is ultimately connected to ground so in the case you refer, the CFGI breaker should trip. In Spain where I live it is imperative by law to have at least one of these with a sensitivity of at least 30mA in homes and small business and 300mA in industries.

[Calambres]

Was it checked as OK at initial installation ?

Yes, it was, and worked OK. Somehow it broke.

[tautech]

Was it checked as OK at initial installation ?

Yes, it was, and worked OK. Somehow it broke.

Hmmm.
Then we best take your advice and check them.
Thanks for bringing this to our attention.

[james_s]

I probably test my GFCI breakers once a year if that. Never in my life have I encountered one that failed to trip. I did have to replace one at my mom's place recently that would trip immediately with nothing plugged in. Replacing the GFCI cured the problem.

You've never encountered one which fails to trip at the massively excessive current applied by the test button. How many times (if ever, since leaving the factory..) have any of those breakers actually had their trip characteristics verified?

I have to assume somebody has verified that. How much current does the test button use? It would not be particularly difficult to apply a known live to ground leak to test it, IIRC the spec is something like 5mA.

Either way I'm not terribly worried about it. My house is old enough that only the bathroom and outside receptacles are GFCI protected, I haven't bothered to update the kitchen. I treat all circuits as if they are unprotected even when I know they are. The GFCI is there as a last resort to hopefully prevent electrocution but I make every effort to never end up in a situation where I need it. Sure it could happen, but so can lots of things.

[helius]

Of course if your finger forms part of a circuit between phase and neutral, the power will still return through neutral and the thing won’t trip.

AFAIK, in Europe the neutral is ultimately connected to ground so in the case you refer, the CFGI breaker should trip. In Spain where I live it is imperative by law to have at least one of these with a sensitivity of at least 30mA in homes and small business and 300mA in industries.

No, the ultimate connection doesn't matter here. What is relevant is the branch currents in the phase (live) and neutral as measured at the RCD/GFCI. Only when they are unequal in magnitude by more than 30mA is the breaker specified to trip. The only way for the branch currents to be unequal is if some current returns to the source by another path: for instance, by taking the protective earth wire if there is an insulation fault, or by taking a path through metal plumbing fixtures if a live wire falls into water. It will also trip if the current returns on the neutral wire of a different branch circuit.

A person putting their finger in a lamp socket, for instance, will bridge between live and neutral, but without a connection to protective earth, there is no way for the measured currents to be unequal in magnitude.

Do you have a pointer to the tester circuit you mentioned?

[Calambres]

I don't know much about the differences between the power grid in USA and Europe but there are no "branches" here. In Europe, if you measure continuity between neutral and earth you'll find a value near zero so if you put a finger in a lamp socket the GFCI should trip, but don't ask me to try   

Regarding the tester circuit I use, first of all I must say that it is not my design. It is a very simple "AC variable dummy load" using a triac:

I took it from a youtube tutorial:



the description is here:

https://100ciaencasa.blogspot.com.es/2018/02/

There you'll find the schematic and the BOM except for a load resistor: RL. If you want to know its value you'll have to get into patreon or... use the Ohm's law    It is there to limit the maximum load the circuit can deliver. I used 4K7 for 50mA with a nominal input tension of 240V (51mA to be precise) and used a 50mA AC analog milliammeter instead of the proposed 30mA panel to prevent it from "pegging" if the failing GFCI goes up to the nominal full scale. All capacitors are for 400V for security. The resistors are 2W except the load resistor (RL) which is 10W also for security reasons. Of course, both links are in spanish.

See my own rendition of that schematic, with english captions, below.

Bear in mind that it is designed for european standard electrical home installations, i.e.: 240V and Schuko base plugs which are not "polarized", that is, you can insert the plug in the base in one way or the other so you're not sure where goes the phase or the neutral and hence the need for the switch. In USA you may skip that section as plugs are "polarized". Here you insert the plug and toggle the switch until you see a nominal reading of about 7 or 8 mA, with the potentiometer fully counterclockwise, of course: then you've selected the phase as the input. If you select the neutral the panel will show no reading at all. Then you must rotate the pot clockwise very slowly reading the panel until the GFCI trips. One better option is to substitute the analog panel for a decent DMM with MAX/MIN. The DMM will then tell you the exact maximum mA just in the moment the GFCI tripped. Don't forget to turn the pot CCW again or disconnect the circuit or you won't be able to reconnect the GFCI back again.

I decided to keep it simple and made it all in a plastic box with the analog panel, which I bought very cheaply in ebay. I'll make a photo of it the next time I visit my bench.

[ElektroQuark]

Of course if your finger forms part of a circuit between phase and neutral, the power will still return through neutral and the thing won’t trip.

AFAIK, in Europe the neutral is ultimately connected to ground so in the case you refer, the CFGI breaker should trip. In Spain where I live it is imperative by law to have at least one of these with a sensitivity of at least 30mA in homes and small business and 300mA in industries.

I'm in Spain too.
I have no neutral but two lives.


BTW, here we call those "differential switches".

[Calambres]

I have to assume somebody has verified that. How much current does the test button use? It would not be particularly difficult to apply a known live to ground leak to test it, IIRC the spec is something like 5mA.

I read somewhere that the test circuit in these buggers are made by an internal 5K 2W resistor. In Europe with a typical 240V line it means that the current is 48mA which is above the nominal maximum current for them. Let's see if I can open the failing unit and look what's inside...

[Calambres]

I'm in Spain too.

I have no neutral but two lives.

Where?... I've never seen such a line topology here (Madrid)

BTW, here we call those "differential switches".

Yes... and hence the title of this topic 

[Whales]

... but the other in my "den"  didn't trip at all, not even at 50mA... although, as I said before, it passed the button test perfectly

That's... curious.   I'll be very interested to see what's going on. 

Either you have two faults (the RCD won't trip until high currents AND the test button pulls a way higher than spec current)  or something more insidious is going on, eg neutral and earth accidentally bonded somewhere on the wrong side of this device.  Either through an appliance or the walls themselves.  That could make the 'near' fault of the RCD test button detectable, but other things (like your test load) plugged into more distant sockets not.  EDIT: no that's ridiculous, the RCD would trip right off from this.

Applying RCD test faults "at the bench" where you work seems like a much better idea than at the panel, in hindsight

[Calambres]

As I already said, I replaced the failing GFCI with a new one and now all is working fine as intended.

It was a very-expensive-highly-reputed-brand GFCI that went south!

[BravoV]

Not sure about there in Spain, but here in Asia, this common and commodity household products are heavily cloned or counterfeited. Usually they're installed by naughty contractors.

Personally I've seen a lot, they've perfected the look & feel, its really hard to differentiate just from the look and touch.

[threephase]

In America the GFCI will be rated to trip at 5mA differential. In Europe it is 30mA, in the UK we refer to the devices as RCDs.

A blog on element14 found a similar issue with a GFI plug and dismantled it.

https://www.element14.com/community/people/jw0752/blog/2017/12/23/reverse-engineering-a-gfi-plug

There are some links to information on RCDs and GFIs in my reply to that blog.

In the UK, recommended testing is 3 monthly using the built in test button and they should be fully tested during initial installation verification and subsequent periodic inspections, which are 10 years for domestic and 3 to 5 for commercial / industrial.

RCDs are not the most reliable of devices, up to a 30% failure rate is not uncommon but it is dependent upon the ambient conditions they are installed in. In the UK, they are regarded as supplementary protection for a circuit but are now mandatory for the majority of new installations or alterations to existing installations.

As to whether or not on would trip if a finger shorted out a lamp holder, I am not totally sure. It will depend upon the leakage from the finger down through the rest of the body to earth in comparison to the current through the finger from live back to neutral. In theory, the current flowing through live and neutral will be the same, so the RCD will not detect that, but the current may exceed the overload rating of the circuit breaker which is likely to be 6A in the UK.

If no overload is detected, then the RCD would detect the leakage current from live, through the body and down to earth and should be enough to trip either a 5mA or a 30mA rated device.

As already stated though, lets leave this one in the theory department and not do any practical tests.

Kind regards

[Calambres]

Not sure about there in Spain, but here in Asia, this common and commodity household products are heavily cloned or counterfeited. Usually they're installed by naughty contractors.

Personally I've seen a lot, they've perfected the look & feel, its really hard to differentiate just from the look and touch.

There are at least two clones of the GFCI that failed that I'm aware of:



Compare it with the original in my first post in this topic. The other brand is CHINT,made in china  Can't find a photo in the web but I have seen it locally in various department stores.

I bought the failing one from a reputed local distributor. I wouldn't swear for my life that it is not a counterfeit but I'm pretty sure it is legit and of a very reputable brand indeed: Schneider Electric, current owners of brands as reputable and legendary as Merlin Gerin or Telemechanique.

ASMOF I bought two and the other is still working like a charm.

[BravoV]

I bought the failing one from a reputed local distributor. I wouldn't swear for my life that it is not a counterfeit but I'm pretty sure it is legitnm and of a very reputable brand indeed: Schneider Electric, current owners of brands as reputable and legendary as Merlin Gerin or Telemechanique.

ASMOF I bought two and the other is still working like a charm.

Here those particular well known international brands like Schneider (Domae) and Merlin Gerlin are so popularly counterfeited, as they're quite pricey compared to less popular or local brands even they're genuine and decent.

[Rerouter]

Here in aus you can buy medical grade outlets with a built in 5 or 10mA RCD inside, Stupidly more expensive, but I've fitted them to the workbench area of my lab, with the isolated lab gear like mounted PSU's instead being on the main 30mA RCD breakers.

So in response I had a walk out and checked, the 5mA trips at about 7, the 10mA trips at 11,

[Calambres]

I've also got a 10mA breaker for a jacuzzi bathtub. It trips at 9mA.

[Scottjd]

I always wonder if there are many people that test these things once a month.
Nowadays that means first shutting down pc's, a couple of NASes, the heating, the alarm system, a mail server, the router, and then run a real risk that one of the many, many connected SMTPs does not come back up after the test.
Who makes time for that 12 times a year?

I do when I can. Besides my computers, NASes and stuff have battery backups. So it’s tests that also. I expect a text and email letting me know the power went out. If I dint get one then I know something downstream failed. I had a UPS that seemed ok, no errors, logs are fine. But when I tested the line this way it failed and just turned off. It was also the one that provided the power battery backup to my network, that the security sits in and cameras also use. So basically if I didn’t test it and the power was cut to the house, the battery backup failed and I had no security or warnings sent to my phone.
Maybe that’s why I test more then most is from the way I run things in my house?

Now I will warn about non UL or non CE tested GFIC’s. I had someone last month ask me to review one for them. It was not even certified or independently tested by any known agency and selling on amazon.
Half the reviews are whorable. I said I would review it but they won’t like the review. I dint know how amazon even lets things like this be sold when it’s people’s life at risk just to save a few dollars.
I understand people don’t want to pay and electrician to replace one, but that doesn’t mean anyone Shoild be able to make and sell an outlet and call it a GFIC, then sell it when that doesn’t meet requirements in the country your buying it. Stiff like this should be illegal to sell to country’s that have requirement and laws about the things being sold.

[james_s]

The main GFCI in my house is built into a receptacle in the garage. About 90% of the time my testing is accidental, I try to plug in an extension cord, reaching through the shelf the receptacle is behind and punch the test button with the ground prong. It's annoying because it resets the clock in the upstairs bathroom.

[tautech]

So with a nagging suspicion about these I've contacted my sparky mate about RCD's (GFCI's) this morning.

For those that must frequently use the Test button, be aware these devices will only meet ratings for x # of cycles.
I haven't done further homework so maybe some brands are better in this regard therefore if you have the need to check/test them frequently it may pay to do some research on the brands that offer best cycle ratings.

This appears to have a similarity with the known phenomenon of MCB performance degradation resulting from frequent overload tripping.

[Dubbie]

Anyone want to speculate on what it is that wears out in these things? From my POV, I can't see any parts that would degrade or wear out with use. It's just coils.

[james_s]

Based on what little I've seen, I would suspect mechanical binding. The next suspect would be an electrolytic capacitor that fails.

[floobydust]

There was a 2001 US NEMA study on residential GFCI failures https://www.mikeholt.com//htmlnews/afci/GFCInema.pdf

I believe it found mains transients (lightning) killed them the most, with SCR/solenoid coil and IC failure, and with years of age, the filter capacitor fails.
Others wired up wrong, had insects, had been painted over, water damage etc.

[gardner]

My experience is in Canada where GFI/RCD breakers are readily available but a bit expensive and GFI/RCD integrated outlets are much cheaper and more commonly used.  Where retrofitting a breaker is an intimidating task for a homeowner, installing a single outlet is a task commonly done by the homeowner or event tenant.  It seems like in some places outside North America that the single outlet style of GFI/RCD is less common or unknown.

As an aside, in the past 15 or so years we've been required to install "arc-fault" breakers -- AFCI -- into circuits serving bedrooms.  These things pick up noise associated with arcing and disconnect the circuit.  They are very expensive.  I'm curious if anyone's seen a teardown or circuit analysis of one of these.

[capt bullshot]

There was a 2001 US NEMA study on residential GFCI failures https://www.mikeholt.com//htmlnews/afci/GFCInema.pdf

I believe it found mains transients (lightning) killed them the most, with SCR/solenoid coil and IC failure, and with years of age, the filter capacitor fails.
Others wired up wrong, had insects, had been painted over, water damage etc.

Nice to know. Our typical 30mA "FI-Schutzschalter" (Fault current protection breaker) is completely electro-mechanic inside (at least the models I know of). So at least the electronics induced failure modes don't apply here.

[CatalinaWOW]

I have had to replace several of the GFI outlets.  Have never done a fault analysis though in more than half of them it was obviously corrosion related due to the damp environment where they were installed.

Because of the high failure rate I am very old school and try to avoid the situations these things are supposed to protect against.  They are at best an imperfect backup.  Use grounded plugs.  Don't operate appliances in the bathtub.  Maintain the integrity of power cords.  If you are showing proper regard for the danger of electricity you should never need one of these things.

[capt bullshot]

As an aside, in the past 15 or so years we've been required to install "arc-fault" breakers -- AFCI -- into circuits serving bedrooms.  These things pick up noise associated with arcing and disconnect the circuit.  They are very expensive.  I'm curious if anyone's seen a teardown or circuit analysis of one of these.

WIth some searching, you might be able to find application notes for a typical chipset (e.g. at TI). It's a rather complex DSP stuff, most probably even more prone to failure than the "electronic" GFCI. And yes, they are expensive, just another example of the "safety mafia" (you can bring up endless arguments if something concerns danger to human life, as practiced by the "Brandschutz" (fire protection) here, and probably everywhere else in the world. They just manage to make the regulations more and more demanding, so they never run out of money they can take from their victims, as the victims are forced to spend the money by law and regulations ...

[james_s]

I hate those arc fault breakers, NEC now requires them on nearly every circuit. They're expensive, they run warm enough that a panel full is dissipating significant power, and they are notorious for nuisance trips. What they really should have done is ban those horrid backstab terminals. I've personally seen several of those burn up, including one in my own house that fortunately burned the end off the wire, opening the circuit before anything else was damaged. I suspect those terminals on the back of receptacles are the cause of most of the arc faults these breakers are meant to detect.

[Monkeh]

My experience is in Canada where GFI/RCD breakers are readily available but a bit expensive and GFI/RCD integrated outlets are much cheaper and more commonly used.  Where retrofitting a breaker is an intimidating task for a homeowner, installing a single outlet is a task commonly done by the homeowner or event tenant.  It seems like in some places outside North America that the single outlet style of GFI/RCD is less common or unknown.

It's a different approach. Most of the rest of the world protects circuits, not outlets - and that means the entire run of the circuit. Over here, RCD protection is required on any circuit which isn't adequately protected from mechanical damage (grounded steel conduit or buried >50mm below all surfaces - both of which are impractical in typical house construction).

[capt bullshot]

I have had to replace several of the GFI outlets.  Have never done a fault analysis though in more than half of them it was obviously corrosion related due to the damp environment where they were installed.

Here these usually are installed at the breaker panel, we don't have the concept of GFI outlets. This eliminates the failure modes you mentioned, and I've rarely (or never) seen a faulty GFCI in a panel.

Because of the high failure rate I am very old school and try to avoid the situations these things are supposed to protect against.  They are at best an imperfect backup.  Use grounded plugs.  Don't operate appliances in the bathtub.  Maintain the integrity of power cords.  If you are showing proper regard for the danger of electricity you should never need one of these things.

Same as I do. I've survived 40 years without having any GFCI installed in the house, just by applying common sense as you describe. Now I've got some, mainly because I had them available and they were easy to install, but I don't feel any safer now. As long as you don't call an electrician to work on your panel, no one is enforced here to comply all the latest rules. An electrician will ask you to let him upgrade your panel if you call him to do some work on your panel and maybe refuse to do his work if you won't let him, but otherwise no one cares.

There's been one case I've installed a CFCI at my parents house for an outdoor circuit. The circuit breaker popped repeatedly there, after some investigation I found some rotten old wiring which caused that. After replacing that, I've installed a GFCI on that circuit to prevent a possible more harmful accident by more failed rotten wiring - these tend to pop way much earlier than your 16A breaker in case of such failures.

I've got a GFCI installed at the subpanel supplying my home lab, but it's reason of existence is to protect my nose from the smoke of failing RIFA Y caps 

BTW - this panel has some contactors used to cut off all lab power supply (manually), so I don't have to care about failing RIFA crackers while I'm not in the lab (by manually cutting all power to the equipment when I'm not present).

[james_s]

There's something to be said for the flexibility of the DIN rail panels used in parts(all?) of Europe/UK. In North American panels you don't have the option of installing contactors and other industrial control devices like that. We also have the rather annoying situation of having several different incompatible breaker panel designs so you have to get a breaker designed to fit in your panel. Most now days use one of 2 or 3 different styles but you still occasionally see oddball panels from the 60s-70s for which breakers are no longer available.

[james_s]

It's a different approach. Most of the rest of the world protects circuits, not outlets - and that means the entire run of the circuit. Over here, RCD protection is required on any circuit which isn't adequately protected from mechanical damage (grounded steel conduit or buried >50mm below all surfaces - both of which are impractical in typical house construction).

The protection is the same either way. GFCI receptacles are normally installed at the start of the run so that all downstream receptacles are also protected. Of course that is not possible with a ringmain configuration which I suspect is the reason the GFCI receptacle is not typically used there.

[capt bullshot]

It's a different approach. Most of the rest of the world protects circuits, not outlets - and that means the entire run of the circuit. Over here, RCD protection is required on any circuit which isn't adequately protected from mechanical damage (grounded steel conduit or buried >50mm below all surfaces - both of which are impractical in typical house construction).

The protection is the same either way. GFCI receptacles are normally installed at the start of the run so that all downstream receptacles are also protected. Of course that is not possible with a ringmain configuration which I suspect is the reason the GFCI receptacle is not typically used there.

Do you speak of connecting the outlets in a ring? Making a ring connection is common for the distribution network on low voltage and medium voltage to give redundancy, but no one does this in a house. Connecting more outlets in a run is common now, in former times there were kind of distribution trees (using junction boxes in the wall). In larger installations you'll find a star topology with many outlets connected to a large panel with many breakers. There may be more RCDs / GFCIs installed in this panel, each one protecting a group of breakers / outlets.

In a house, you'll find everything ranging from no GFCI at all to one protecting all circuits (which can be quite nasty). More thoughtfully arranged installations will have one or two GFCIs at the main panel protecting outdoor circuits and bathrooms / kitchen. Regulations change constantly, so depending on the age, the style varies.

[Monkeh]

It's a different approach. Most of the rest of the world protects circuits, not outlets - and that means the entire run of the circuit. Over here, RCD protection is required on any circuit which isn't adequately protected from mechanical damage (grounded steel conduit or buried >50mm below all surfaces - both of which are impractical in typical house construction).

The protection is the same either way. GFCI receptacles are normally installed at the start of the run so that all downstream receptacles are also protected. Of course that is not possible with a ringmain configuration which I suspect is the reason the GFCI receptacle is not typically used there.

Placing the protection at the first outlet does not protect the circuit. You still have the run back to the panel - as I said, we protect the circuit, that means the cabling as well, not just items connected at outlets. We certainly have RCD sockets:


But as mentioned, that does not fulfill the requirement to protect the circuit (in fact, there's usually no protected output as the circuit can be up to 32A).

Do you speak of connecting the outlets in a ring? Making a ring connection is common for the distribution network on low voltage and medium voltage to give redundancy, but no one does this in a house.

Oh, yes, they do. Quite intentionally.

[james_s]

Placing the protection at the first outlet does not protect the circuit. You still have the run back to the panel - as I said, we protect the circuit, that means the cabling as well, not just items connected at outlets. We certainly have

I fail to see why this is an issue, how often does one need ground fault protection of a wire that is running through a wall? As long as anything connected to the circuit is downstream of the GFCI then it is protected. In my case my house built in 1979 has a single original GFCI receptacle in the garage which feeds all of the bathroom receptacles and the one out on the back deck. The only unprotected portion of that circuit is about 8 feet of wire that runs through the wall from the panel to the GFCI receptacle. Nowhere is the unprotected cable accessible, and it's still protected from overload by the breaker in the panel. The GFCI is secondary protection and not something that should be relied on, it was only about 40 years ago that they started showing up and only around 20 years ago that they had to be used anywhere other than outdoors and in bathrooms.

[Monkeh]

Placing the protection at the first outlet does not protect the circuit. You still have the run back to the panel - as I said, we protect the circuit, that means the cabling as well, not just items connected at outlets. We certainly have

I fail to see why this is an issue, how often does one need ground fault protection of a wire that is running through a wall?

How often do idiots go poking random nails and screws into walls? The answer is all the fucking time. And when you have houses where the primary construction is brick, not timber, the odds of putting one into a cable go up.

[james_s]

Where a wire passes through a stud it is required to be protected by a nail plate, these are steel plates you nail over the stud at the point where a wire passes through it. The exception to this is if the wire is armored cable or run through metal conduit. Driving nails or screws into wires is virtually unheard of, and relying on a GFCI to protect against that situation rather than preventing it from happening is ridiculous. Not to mention GFCIs here are only used on wet location circuits, a majority of wires run through homes and businesses are not GFCI protected, there's just little reason for it.

[tautech]

Where a wire passes through a stud it is required to be protected by a nail plate, these are steel plates you nail over the stud at the point where a wire passes through it.

You make that statement like it's a universal requirement which I inform it's not, not in NZ anyway.

Driving nails or screws into wires is virtually unheard of, and relying on a GFCI to protect against that situation rather than preventing it from happening is ridiculous.

I've actually seen that happen in new builds and renovations.
 

Not to mention GFCIs here are only used on wet location circuits, a majority of wires run through homes and businesses are not GFCI protected, there's just little reason for it.

That used to be the case here in NZ but recent regs require RCD (GFCI) protection on all new builds.
Any added outlets to existing too.


I like many consider them unnecessary to knowledgeable, safe or proper use of an outlet.

[steverino]

Excuse my ignorance, and this may have been mentioned, but are all circuits in GB, Auz, Europe protected by RCDs (newer codes, of course).

[Monkeh]

Where a wire passes through a stud

Let me just stop you there and point to my concrete block walls.

[james_s]

We don't run wires directly through concrete block walls here, they must be in metal conduit or armored cable which has a flexible spiral wound steel jacket. Normally with a concrete or cinder block wall the wiring would all be done on the surface using metal conduit with individual conductors. You can only run non-metallic cable through wood studs and it must be protected by a nail plate or conduit anywhere that it passes less than a certain distance from the surface. Any situation where a hapless homeowner could potentially penetrate the cable without going to extreme efforts is a code violation, not to mention it strikes me as common sense to prevent such an incident rather than try to band-aid over it with a ground fault protector.

[Monkeh]

And won't that just look fantastic in the living room.

And with that all said, let me once again bring you back to the concept of protecting the circuit, not random pieces of it with a randomly placed device.

[tautech]

We don't run wires directly through concrete block walls here, they must be in metal conduit or armored cable which has a flexible spiral wound steel jacket. Normally with a concrete or cinder block wall the wiring would all be done on the surface using metal conduit with individual conductors. You can only run non-metallic cable through wood studs and it must be protected by a nail plate or conduit anywhere that it passes less than a certain distance from the surface. Any situation where a hapless homeowner could potentially penetrate the cable without going to extreme efforts is a code violation, not to mention it strikes me as common sense to prevent such an incident rather than try to band-aid over it with a ground fault protector.

Hell that seems like a massive overkill ! 

Here it's just in ABS electrical conduit, in concrete, surface mount (exposed) and even plastic flexy (when needed) for plant wiring and only if any of it is within 2m of reach.

[Monkeh]

We don't run wires directly through concrete block walls here, they must be in metal conduit or armored cable which has a flexible spiral wound steel jacket. Normally with a concrete or cinder block wall the wiring would all be done on the surface using metal conduit with individual conductors. You can only run non-metallic cable through wood studs and it must be protected by a nail plate or conduit anywhere that it passes less than a certain distance from the surface. Any situation where a hapless homeowner could potentially penetrate the cable without going to extreme efforts is a code violation, not to mention it strikes me as common sense to prevent such an incident rather than try to band-aid over it with a ground fault protector.

Hell that seems like a massive overkill ! 

Here it's just in ABS electrical conduit, in concrete, surface mount (exposed) and even plastic flexy (when needed) for plant wiring and only if any of it is within 2m of reach.

The yanks seem to pivot from cheap and nasty strung through the walls straight to violently industrial (dated industrial, but industrial..) overkill. Moving forwards is not really a thing except for kneejerking like AFCIs.

[james_s]

A living room made with concrete block walls would be extremely rare here, in most of North America houses are built out of wood. In the East where brick and masonry is much more common there will still be wood studded walls on the inside providing a gap for the required insulation as well as electrical and plumbing. If the gap is less than a certain width (1 7/8" from memory) then the wire must be armored cable or in conduit. The only place you'd find exposed concrete walls is in a basement or garage, and again conduit or armored cable is required for obvious reasons.

I really feel like you're arguing for the sake of arguing, or at least being willfully ignorant of the differing construction methods here and not looking at a building from a holistic standpoint. Unless you can find examples (heck even one example?) of people being electrocuted in North American by ground faults in indoor wiring due to a lack of GFCI protection. Most circuits in homes here do not have GFCI protection at all, it is only used for receptacles that are within a certain distance of a sink, tub or other water source and outdoors. In a typical home you might have 15-20 circuits, in older homes one will be GFCI protected for the bathroom receptacles and newer homes will have at least 2 more for the kitchen receptacles and any receptacle in an unoccupied basement or garage must also be GFCI protected. In about 95% of cases this is done by a GFCI receptacle at the start of the run though GFCI breakers are available they are much more expensive and typically only used in high end homes and commercial buildings. It's only used when something connected to the circuit is expected to be used in or around a water source.

It's really a non-issue, ground faults in the wiring from the panel to the receptacle are something that's so rare that if it happens at all it would be considered a crazy fluke. I mean if you've got 10-20 non-GFCI circuits who's going to worry if one more has a few feet of cable in a wall that isn't protected from a bizarre edge case? Someone is negligent enough to run un-protected cable near enough to the surface that someone could hit it by hanging a picture? That's absolute madness, it's illegal to do so, and for a very good reason. No protection device should ever be relied on to prevent injury in such a case, the cable must be physically protected, if ground fault protection is used it is secondary protection like an airbag in a car. Just because you have an airbag doesn't mean you don't bother wearing a seatbelt and just drive as carelessly as you like because you've got a device to protect you. It increases your chance of surviving an incident but it is far better to prevent the incident in the first place.

[james_s]

Hell that seems like a massive overkill ! 

Here it's just in ABS electrical conduit, in concrete, surface mount (exposed) and even plastic flexy (when needed) for plant wiring and only if any of it is within 2m of reach.

It's overkill because it's such an unusual application. In probably 99% of houses in the US built within the last 50 years all of the wiring is NM cable run through wooden studs in the walls, floors and ceilings. In most homes there will be one receptacle and a light in the garage as standard, installed in one of the wooden studded walls. In a basement most of the wiring will be run through the ceiling joists, if there is a bare concrete wall then the drop has to be protected in conduit but this is rare. If you add something after the house is built and the wire can't be run through the wall then conduit or armored cable is typically used. PVC conduit is acceptable too but not as protection from nails and screws. Wood is abundant here, our houses are built out of wood, even if the exterior is brick the interior framing is wood, that's just how it is. I've never in my life seen a house made of cinder blocks, we just don't build them like that, especially in earthquake zones here on the coast. One could argue all day which system is better, but the fact is they all work, and the whole GFCI thing is a relatively recent development, they have only existed for around 40 years and even today they are not something that one would use in the absence of water.

Regardless of all that, I cannot fathom how anyone could find it acceptable to run non-armored cable such that someone could easily run a nail through it, I mean even with the best protective devices in the world that is still negligent when providing some sort of protection is trivial, why beg for an accident? Armored flex is inexpensive, conduit and metal raceway is cheap and readily available, it's very cheap protection that prevents all manner of situations that a simple GFCI might not help with.

[Monkeh]

I gave up on a longer post.

I'm not telling you you're doing it wrong. I'm just trying to explain some of the reasons we do it differently. You're just not seeing it. All you see are stud walls. I'm trying not to knock a brick one down hitting it with my head.

[james_s]

But you were complaining about the dangers of having unprotected wiring between the panel and the GFCI, which I've been trying to explain is not an issue here because the way everything else is done here makes it extraordinarily unlikely for a situation to occur where placing the GFCI in the panel would prevent it.

For what it's worth, I prefer to have the GFCI breaker in the panel where everything is centralized rather than spread all over in individual receptacles. It's especially fun when someone manages to install two GFCI receptacles in the same run and then you get to hunt down the one hidden behind a bookcase that has tripped. When I install one I spend the extra money on the panel mounted breaker, and I also use top notch spec grade or occasionally hospital grade receptacles, they're much better quality than the cheap home center stuff you find in cookie cutter homes.

[Monkeh]

But you were complaining about the dangers of having unprotected wiring between the panel and the GFCI, which I've been trying to explain is not an issue here because the way everything else is done here makes it extraordinarily unlikely for a situation to occur where placing the GFCI in the panel would prevent it.

.. I was pointing out that as we protect circuits, and our installation methods are different, that's not a valid method for us.

[capt bullshot]

Do you speak of connecting the outlets in a ring? Making a ring connection is common for the distribution network on low voltage and medium voltage to give redundancy, but no one does this in a house.

Oh, yes, they do. Quite intentionally.

That's interesting. Where and for what reason does one wire outlets in a ring?

[helius]

After WWII there was a worldwide copper shortage. Some countries responded by installing aluminum wiring, and others used ring mains, which use less copper per outlet. The UK adopted the latter option. Hindsight indicates that ring mains were a far better and long-lived solution than aluminum wires.

[Dubbie]

Having steel armored cable in all walls here would massively massively exceed the cost of GFCIs for all the circuits.

Electrical supplies are very expensive here in NZ compared to the USA

[Shock]

So I guess there is a lesson here for the people who kept blindly recommending relying only on GFCI type devices to provide bench safety when working on mains power devices.

I believe the proper test here is performed at the outlet and not just tripping the circuit breakers at the switchboard, but repeated testing is not mandatory.

From what I have seen the UK safety standards seem quite advanced, Aust/NZ is very good we don't have fused plugs but also don't suffer from their downsides. I'm not entirely familiar with the US code but based on youtube videos existing installations seem a bit cobbled together and scary at times.

[Fred27]

My breakers are of anything a little too sensitive. When doing some electrical DIY I obviously cut off the power to the circuit I'm working on. Often when I touch the neutral the breaker will trip.

My UK wiring has a breaker for all the power circuits and then separate isolation switches for the live on each circuit. Hence I can be working on the garage (safe) but the rest of the house is powered up with the breaker protecting it.

I'm assuming (possibly incorrectly) that I'm acting as an aerial and injecting a few unexpected mA into the neutral on the "disconnected" circuit.

[HoracioDos]

There you'll find the schematic and the BOM except for a load resistor: RL. If you want to know its value you'll have to get into patreon or... use the Ohm's law

Thanks for your post. You gave me a project to play with the mains.  LOL. Don't worry I have due respect to the mains.
I usually test the differential switch and sockets with a UNI-T18D (I should ask Joe Smith if I have a suicidal conduct). It has a built in RCD test but I don't know if the RCD trips bellow 30mA or how fast it does. For a nominal 220V, I guess RL should be 4.4K according to your circuit.

[Calambres]

It depends on what current limit you want for the circuit. I opted for a 50mA panel so I used 4.7K for a 51mA limit.

 Just use Ohm's law:

220V and 50mA need a 4.4K (11W) resistor which is not standard.  Use a 4K7 / 10W resistor for 46.8mA (a bit over 10W) and you're fine.

[Calambres]

This is my GFCI tester, as promised: