Author Topic: Beware of your differential circuit breakers (GFCI)!  (Read 3031 times)

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Offline Calambres

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #25 on: May 26, 2018, 05:10:58 pm »
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  :)

Offline Whales

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #26 on: May 26, 2018, 05:19:35 pm »
Quote
... 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 :D
« Last Edit: May 26, 2018, 05:21:54 pm by Whales »
 

Offline Calambres

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #27 on: May 26, 2018, 05:30:40 pm »
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!
« Last Edit: May 26, 2018, 05:34:39 pm by Calambres »
 

Online BravoV

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #28 on: May 26, 2018, 05:44:30 pm »
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.
« Last Edit: May 26, 2018, 05:46:15 pm by BravoV »
 

Offline threephase

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #29 on: May 26, 2018, 06:14:47 pm »
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.

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Offline Calambres

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #30 on: May 26, 2018, 06:20:18 pm »
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.
« Last Edit: May 26, 2018, 06:32:50 pm by Calambres »
 

Online BravoV

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #31 on: May 26, 2018, 06:27:23 pm »
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.
 

Offline Rerouter

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #32 on: May 26, 2018, 06:33:08 pm »
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,
 

Offline Calambres

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #33 on: May 26, 2018, 06:50:55 pm »
I've also got a 10mA breaker for a jacuzzi bathtub. It trips at 9mA.

Offline Scottjd

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Re: Beware of your differential circuit breakers!
« Reply #34 on: May 27, 2018, 10:59:12 pm »
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.
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Offline james_s

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #35 on: May 28, 2018, 07:35:59 am »
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.
 

Offline tautech

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #36 on: May 28, 2018, 08:28:46 am »
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.
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Offline Dubbie

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #37 on: May 28, 2018, 02:08:45 pm »
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.
 

Offline james_s

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #38 on: May 28, 2018, 02:21:14 pm »
Based on what little I've seen, I would suspect mechanical binding. The next suspect would be an electrolytic capacitor that fails.
 

Offline floobydust

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #39 on: May 28, 2018, 02:48:36 pm »
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.
 

Offline gardner

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #40 on: May 29, 2018, 12:44:54 am »
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.
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Online capt bullshot

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #41 on: May 29, 2018, 12:47:38 am »
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.
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Online CatalinaWOW

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #42 on: May 29, 2018, 12:52:08 am »
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.
 

Online capt bullshot

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #43 on: May 29, 2018, 12:52:14 am »
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 ...
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Offline james_s

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #44 on: May 29, 2018, 01:50:52 am »
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.
 
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Online Monkeh

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #45 on: May 29, 2018, 03:09:32 am »
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).
 

Online capt bullshot

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #46 on: May 29, 2018, 03:11:17 am »
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.

Quote
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  8)

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).



« Last Edit: May 29, 2018, 03:16:20 am by capt bullshot »
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Offline james_s

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #47 on: May 29, 2018, 08:19:57 am »
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.
 

Offline james_s

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #48 on: May 29, 2018, 08:23:17 am »

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.
 

Online capt bullshot

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Re: Beware of your differential circuit breakers (GFCI)!
« Reply #49 on: May 29, 2018, 08:31:00 am »

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.


« Last Edit: May 29, 2018, 08:34:31 am by capt bullshot »
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