Talk:Residual-current device

message: From the article:
:Manufacturers are now designing such devices that will disconnect their circuit, even if they don't dectect electrical leaking, if they are wired improperly. 
Really? How? Under all possible miswirings, or only some? -- The Anome 08:50, 26 May 2004 (UTC)
replies: text: I don't understand this either.  It's just a guess on my part, but since the most common wiring error is reversal of line and load connections on receptacle devices, the manufacturers may be doing something to detect that particular condition and trip.  UninvitedCompany 14:44, 26 May 2004 (UTC)

text: Some types of RCD incorporate an additional device which trips if the voltage between the earth (ground) and neutral conductors rises above a certain potential. This would also detect a miswiring where the live (hot) and neutral conductors were reversed. --Ali@gwc.org.uk 13:20, 17 Jul 2004 (UTC)
thread_title: miswirings

message: I'm concerned by the comments at the bottom that suggest that, in the US, you can intermix line voltage wiring with Ethernet, etc. I'm not aware of *ANY* US code-approved wiring solution that allows that, although I suppose a partitioned mounting box might allow the use of a single Decora faceplate with, say, line voltage components on one side and low-voltage components on the other side.
Any NEC experts here to say yea or nay?
Atlant 18:25, 13 Dec 2004 (UTC)
replies: text: Yes, the low-voltage stuff is either on the other side of a divider or, commonly, outside the box altogether, but sharing a common (large) faceplate. I have edited this section and simply deleted the refs to low-voltage wiring; it's not particularly common and has no special relevance to this article.  Sharkford 19:12, 1 February 2006 (UTC)
thread_title: mixing mains and signal wiring in us

message: Here in the U.S., we're starting to see circuit breakers that are able to sense arcing current. (I don't know exactly how they do this, but I'd assume it depends on sensing high-frequency noise in the mains current waveform.) I think this capability is often combined with Balanced-Current fault detection.
Does anyone feel ambitious enough to investigate this and either 1) create a AFI redirect and modify this article to include the concept or 2) create a free-standing article with appropriate cross-references to here and back?
Atlant 12:18, 30 Mar 2005 (UTC)
thread_title: Arc-Fault Interrupter

message: Using the example of the illustrated "outlet-style" RCD, the description used to speak about the solenoid being continuously energized and that providing the latch that kept the RCD "reset". This description is clearly inconsistent with at least US-style RCDs as it would imply that a power failure would also lead to the dropping-out of all of the RCD solenoids, their subsequent tripping, and the need to manually reset all the RCDs after power was restored. This ain't the way it works in practice.
I conclude from this that the mechanism operates in the opposite fashion: The latch is mechanically held and the RCD activates the solenoid when it wants to "trip" the RCD by unlatching the latch. I've changed the text to reflect this view of the world. But if Europe has "outlet-style" RCDS and they operate as originally described, please feel free to extend the text to explain this.
Meanwhile, I guess I'll take an American RCD apart this week-end and check for certain. :-) 
Atlant 19:27, 3 Jun 2005 (UTC)
replies: text: In Europe you can get both passive rcds (which don't trip out on power failure) and active rcds (which do). Generally most rcds in consumer units etc are the passive type but the active type is considered advisible for supplying equipment which can pose a danger on unexpected re-energistation. Plugwash 20:57, 3 Jun 2005 (UTC)
thread_title:  How do RCDs actually trip? 

message: :"Residual current devices (RCD) or residual current circuit breakers (RCCB) are circuit breakers that operate to disconnect their circuit whenever they detect that current leaking out of the circuit (such as current leaking to earth through a ground fault) exceeds safety limits."
dd  —Preceding unsigned comment added by 87.218.117.82 (talk) 15:15, 3 October 2007 (UTC)
thread_title: Leakage limits: real safety or imaginary?

message: Atlant:
:I'm afraid you're not considering all the possibilities. Let's take, for example, my hot tub.
Every imaginable combination of faults and design errors is possible. We could sit here and think up scenarios by the score - but sooner or later one notices that some of these scenarios are common, some rare, and some simply dont happen IRL. Thus what scenario we can think of is not what determines level of risk.
What does determine level of risk is how many people are dying in real life from these imagined scenarios. The one you pose here is not one that is hapenning here in the UK, thus, by elementary logical deduction, it is not a significant risk.
Real world risk is best determined by looking at the facts, not by imagining what scenarios might or might not happen. Its a common mistake.
Tabby
Tabby 22:50, 15 Sep 2005 (UTC)
thread_title: How to Evaluate Risk

message: There is no question that RCDs have saved lives. It is also clear that RCDs have cost lives, and will continue to. The questions are:
1. which number will be bigger over the many years to come, will they save more or kill more?
2. could the cost of millions of RCDs be better spent elsewhere, eg on non slip stair treads? Stairs injure and kill lots of people, electrics dont (in UK).
Tabby
PS I agree with your comment that escape lighting should not be on RCD, but here in UK is routinely is. We have an ongoing history of mandated whole building RCDs too.
Tabby 22:51, 15 Sep 2005 (UTC)
replies: text: The only time it is mandated by the electrical regs for everything to be on a RCD is a TT system and in a TT system it really is important to have everything on RCD (or voltage operated ELCB but those had big problems of thier own) but even then it is considered very bad practice to just have one RCD in the system. The reason the horrible practice of one rcd covering everything became common was simply cost. Plugwash 20:16, 11 September 2007 (UTC)
thread_title: Re RCDs saving lives

message: I accept the points of those who say that ELCB is not technically accurate but at least it is descriptive. I haven't been able to figure out what "residual" means. Any ideas? Harmonitron
:THe residual current is the difference between the phase current and the neutral current. There shouldnt be any diff if you have no leakage to earth. But if there is a leakage it means some normally earthed part is live, and this will be sensed by the balanced coil and trip out.--Light current 23:51, 23 April 2006 (UTC)
thread_title: What is the "residual" in RCD?

message: IMO it doesnt--Light current 23:48, 23 April 2006 (UTC)
thread_title:  How does earth leakage circuit breaker differs from residual current circuit breaker 

message: at this forum thread lots of different names for RCDs in English have been listed. TERdON 22:36, 8 May 2006 (UTC)
thread_title:  alternative names for the device 

message: I added this article to the category Electrical safety because I belive people looking for information on GFCI/RCDs are apt to look in that category.Gerry Ashton 14:34, 25 May 2006 (UTC)
thread_title: Category: Electrical safety

message: The article doesn't seem to mention anything about Australia's regulations, so the short version:
RCDs must trip at no more that 30mA within 20ms (this is because anything over 35mA is likely to kill a person if it goes through their heart). RCDs must be installed for any new circuits added to a domestic situation (this includes lighting circuits).  The only exception to this is where it would be deemed to add greater risk (such as emergency lighting or smoke alarms.)  Also, if there is only one appliance wired into a circuit, it does not require an RCD (eg - an oven). It is common practice for electricians to run a dedicated circuit for older fridges that do not pose a risk.  Also, RCD's are usually refered to as Safety Switches by the general public.
Hope that added to the info. Blaab 10:34, 28 September 2006 (UTC)
thread_title: RCDs in Australia

message: These values were set by tests at Underwriters Laboratories during which volunteers holding cups of rice were subjected to shocks of known amperage and voltage.
What's the purpose of the rice?  Is this possibly a joke?198.99.123.63 22:50, 29 November 2006 (UTC)
thread_title:  Cups of Rice? 

message: Our home was struck by lightning last night and I found it very interesting that every GFI unit in the home tripped and appears to have saved many of the items they powered.  Our 2001 home has several GFI’s.  Things that were not using a GFI receptacle were damaged unless they had a surge arrestor built-in.  I believe the lightning struck the powered attic vent or the gas water heater’s metal smokestack.  The family could feel the electricity..  —Preceding unsigned comment added by 166.128.23.198 (talk) 16:52, 24 April 2008 (UTC)
replies: text: If the company, who wired your home, done everything honestly, they have put dischargers, which accept all lighting to themself and redirect it to the earth. As there was too high current in ground wire during lighthing, CFI felt it and disenergized circuits 90.191.190.76 (talk) 17:38, 13 December 2010 (UTC)
thread_title:  Lightning 

message: Should we have a picture of a GFCI receptacle for this section?  In the US, these devices are quite common.
76.179.147.161 (talk) 20:46, 19 July 2008 (UTC)
thread_title:  Picture of GFCI receptacle? 

message: I do not understand the section entitled "Surge current resistance [in A]":
:Peak current an RCD is designed to withstand (8/20 µs impulse). The IEC 61008 and IEC 61009 standards impose the use of a 0.5 µs/ 100 kHz damped oscillator wave (ring wave) to test the ability of residual current protection devices to withstand operational discharges with a peak current equal to 200 A. With regard to atmospheric discharges, IEC 61008 and 61009 standards establish the 8/20 µs surge current test with 3000 A peak current but limit the requirement to RCDs classified as Selective.
What is an 8/20 µs impulse? What is a "0.5 µs/ 100 kHz damped oscillator wave (ring wave)"? (Note that 100 kHz has a period of 10 μs.) What atmospheric discharge is it talking about? What exactly do IEC 61008 and 61009 concern, respectively?
Eric Kvaalen (talk) 17:32, 2 August 2008 (UTC)
replies: text: I've rephrased that first sentence, it was unforgiveably jargon-y for a general reference encyclopedia. The 8/20 us impulse refers to a common shape of pulse used for electrical testing. --Wtshymanski (talk) 19:45, 2 August 2008 (UTC)
thread_title:  Surge resistance 

message: The current picture of the internals of the RCD is quite small, a larger picture would be nice.  —Preceding unsigned comment added by 89.236.35.232 (talk) 13:20, 14 April 2009 (UTC)
thread_title:  Bigger picture of internals of RCD needed 

message: in the picture test button winding
is incorrectly connected only
to one side of torroid (both are up)
---------------
-supposed to connect on
one to up - other to the lower side  —Preceding unsigned comment added by 88.196.129.215 (talk) 22:27, 16 June 2010 (UTC)
thread_title:  3-phase picture 

message: 3-phase.JPG  —Preceding unsigned comment added by 88.196.129.215 (talk) 22:58, 16 June 2010 (UTC)
thread_title:  3-phase picture(corrected one) 

message: For revision on Feb 13 2012 The first paragraph on this article lists so many names and abbreviations that it is hard to read it without misunderstanding something. The information may be correct and possibly worth noting but with this many names I would have put information on alternate names in its own section, not in the first paragraph. Even if it deserves to be in the top paragraph it perhaps ought to have a better layout than it has now.  — Preceding unsigned comment added by 86.13.97.89 (talk) 14:02, 13 February 2012 (UTC)
thread_title:  Confusion in top paragraph 

message: Whole installations on a single RCD, common in the UK, are prone to nuisance trips that can cause safety problems with loss of lighting and defrosting of food. RCDs also cause nuisance trips with appliances where earth leakage is common and not a cause of injury or mortality, such as water heaters. However such nuisance trips are easily corrected by removing the problem (such as a blown light bulb) and re-setting the RCD.
The last sentence is quite incorrect
# blown lightbulbs are open circuit loads, removing them has nothing to do with resolving earth leakage issues
# problems causing RCD trips are known for being not easy to correct, generally speaking
# In the case of water heater leakage, it would be unrealistic to describe the solution as easily corrected and reset the rcd.
So I removed the faulty sentence.
 This RCD contains a resistor with an improper value in the test circuit, which gives incorrect results for testing. Under certain circumstances it may prove lethal because it will not trip when expected. That is why RCDs should be tested by the socket tester with calibrated leakage
This makes little sense. I've not corrected it, as I didn't know what point the author. was trying to make.
Tabby (talk)
:
:As well as I know, tradition is for 5ma in the US and 30ma in Europe. Though with the different line voltage and plugs, people won't be using testers in the wrong system. Gah4 (talk) 21:31, 7 March 2021 (UTC)
thread_title:  2 errors 

message: "MCB" is not a universal explanation of a circuit breaker.  Professional electricians across North America will never run into that terminology unless they speak with an electrician outside of that area.  "MCB" should be linked to a correct page or explained as to what it is.  — Preceding unsigned comment added by 208.65.73.107 (talk) 21:36, 28 February 2013 (UTC)
replies: text: Although that's not what it means  (in this article, at least). Andy Dingley (talk) 19:56, 16 December 2019 (UTC)
thread_title:  What is an MCB? 

message: The history section in the german version of this article ("Fehlerstromschutzschalte") goes back quite a bit further
than to south africa 1955: 
Der Fehlerstromschutzschalter wurde bereits 1903 von Schuckert unter der Bezeichnung Summenstromschaltung zur Erdschlusserfassung patentiert (DRP-Nr. 160.069).[20] Kuhlmann beschreibt bei AEG eine Methode zur Messung der Erdschlussströme im Berliner Netz. Weiterentwickelt wird die Technik, auf der auch heutige Fehlerstromschutzschalter basieren, von Nicholsen (1908, USA-Pat-Nr. 959.787).[21]
Maybe this should be revised in the english article?  — Preceding unsigned comment added by 159.168.7.148 (talk) 10:36, 8 April 2013 (UTC)
thread_title:  History section correct? 

message: Undid revision 588089932 by TinyMark (talk) RCDs are used for earth fault protection. See talk.
RCDs are very much used for protection against short circuits to earth. See below link for reference. In the case of TT installations, where there is no metallic earth return to the supply transformer, the earth loop impedance may be too high to trip a circuit breaker, which is why RCDs are used for additional protection, typically with a 100 or 500 mA trip current, as compared to the 30 mA typically used for protection against electric shock. 
http://www05.abb.com/global/scot/scot209.nsf/veritydisplay/c4e584f06cc6c4fbc1257ad800496193/$file/2CSC420004B0201_RCDs%20EN.pdf
:I'm having problems with the terminology here. I must admit that I never had anything to do with these things when I lived in the UK. But surely, in a TT system, the circuit cannot be shorted to earth because a the circuit is not shorted, i.e. the current does not return directly to where it came from????? TINYMARK 12:14, 29 December 2013 (UTC)
replies: text: If I recall the regulations do not use the term short circuit; it is simply referred to as a fault. But short circuit defines the term as current flowing along an unintended path, which is what happens - in the event of such a fault the current flows directly through the mass of earth to the supply transformer (usually via the earth electrodes). It's not relevant that that path isn't a metallic path. The RCD is used because depending on the local conditions the fault current may be only a few amps, which means a normal circuit breaker could take a long time to trip, or not trip at all. The circuit breaker is still relevant and used to provide overload protection and protection from phase-phase or phase-neutral faults. Alistair1978 (talk) 12:28, 29 December 2013 (UTC)
replies: text: Well I have been living in Germany for ages now. The circuit breakers are marked with LS (Leitungsschutz) meaning that they are there to protect the power cable - from burning out or causing a fire, I assume. This will not happen with a higher resistance short as you described as the current is too low. Although a fault is present and the RCD will trip - but what is being protected??? TINYMARK 12:52, 29 December 2013 (UTC)
replies: text: It's for preventing fire at the location of the fault (see page 16 of the PDF linked above). Otherwise, a fault to earth could deliver say 10 amps continuously, which might not melt the supply cabling but could easily cause a fire at the point of fault, as well as causing rise of earth potential which could cause a risk of electric shock. Note that such TT supplies are very common in the UK in rural installations with overhead supplies. Alistair1978 (talk) 14:19, 29 December 2013 (UTC)
replies: text: Thanks Alistair. My mum's flat is on the first (top) floor of a house and I (2m) could reach up and touch the lines coming into the house! Obviously a TT system, but with very iffy plastic sleeves on the lines. In Germany TT systems are usually only in factories etc. TINYMARK 15:36, 29 December 2013 (UTC)
thread_title:  Use of RCDs for protection against shorts to earth 

message: A residual-current device (RCD), or residual-current circuit breaker (RCCB), is a device that instantly breaks an electric circuit to prevent serious harm from an ongoing electric shock. A fuse or circuit breaker also does that,  'instantly' of course, is subject to qualification.  How fast a fuse or breaker reacts depends on its profile and the degree of overcurrent in the circuit.  They can be made as fact as they need to be.
An RCD also has a reaction time that can vary.  Actually, it needn't be any faster than a breaker.  That's not how it protects against electrocution.
That sentence is bad; it misses the issue.  Sbalfour (talk) 23:51, 14 November 2017 (UTC)
thread_title:  Lead opening sentence is iffy 

message: It seems that there is now LCDI, Leakage Current Detector Interrupter, designed to detect faulty power cords. They are required for some portable air conditioners. My understanding is that they put some wire mesh inside the power cord, and outside the actual conductors. If current goes into it, then there is a fault in the cord. That seems somewhat different from RCD or GFI, but maybe it could redirect here. It seems like they can also use Arc Fault Detectors instead, which I think are not well described here, but might be, or might have their own article. Gah4 (talk) 09:57, 20 March 2021 (UTC)
replies: text: Is there an official definition of an LCDI somewhere, perhaps in the requirements for its presence in certain appliances such as air conditioners? My current understanding of an LCDI is that it is a dedicated GFCI installed together with a mesh-shielded power cord. Please correct or refine this impression if necessary.  Reify-tech (talk) 15:07, 23 September 2021 (UTC)
thread_title:  LCDI 

message: Hi,
The second paragraph has the claim:
"Alternating 120-volt current above 20 mA (0.020 amperes) through the human body is potentially sufficient to cause cardiac arrest or serious harm if it persists for more than a small fraction of a second."
Where is the citation for this?
Thank you,
James Pedersen
james00090@gmail.com  — Preceding unsigned comment added by Watcher00090 (talk • contribs) 03:11, 23 March 2022 (UTC)
thread_title:  Can we please have a citation for a claim in the second paragraph? 

message: No mention of how certain devices such as certain styles of electric motors causing nuisance trips? 71.173.19.20 (talk) 15:33, 6 June 2022 (UTC)
thread_title:  Motors 

message: There is no mention of SI (super immunised) RCDs. My understanding is that these are a subclass of Type A RCDs, but that they provide more resistance to nuisance tripping.
I have no idea whether these are standardised, or whether they are manufacturer-specific. As a result I am hesitant to add this type to the article since I don't have access to the IEC standard.
Found these links though:
https://www.farnell.com/datasheets/607776.pdf
https://www.electrical-installation.org/enwiki/Sensitivity_of_RCDs_to_disturbances
JanCeuleers (talk) 17:35, 18 March 2023 (UTC)
thread_title:  Type A-SI 

message: There is no discussion of this topic which is becoming important in solar installations where the current can flow in either direction. Apparently some types of RCD are unidirectional and some bidirectional. It would be good for wikipedia to cover this if possible. I do not know enough to provide any guidance. 31.185.161.39 (talk) 22:24, 10 May 2024 (UTC)
thread_title:  uni or bi directional RCDs