Talk:Residual-current device

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[edit] GFI/GFCI

From the article:

The terms ground fault circuit interrupter (GFCI) or ground fault interrupter (GFI) are used in the United States and Canada, but these terms are not, strictly speaking, correct (or at least complete), because a RCD will trip if current leaks anywhere, not just to ground.

In NEC terminology, power flows between the "ungrounded conductor" and the "grounded conductor" (with the load in the middle) . If more power is flowing through the ungrounded conductor then the grounded conductor (unbalanced), then there is a ground fault (a failure to ground properly), and so the circuit should be interrupted. Looking at it this way, the terms GFCI and GFI make more sense, and is how I always assumed they came about.

Notes: The "ungrounded conductor" is colloquially called "hot" or "line". The "grounded conductor" is also called the "identified conductor", and is colloquially (and sometimes incorrectly) called "neutral". Note that none of these are the "equipment grounding conductor", which is colloquially called "safety ground" or just "ground". Yes, NEC terminology is confusing.

--DragonHawk 15:23, 19 Jun 2005 (UTC)

But ground isn't the only place the errant current can go; it might return on the other hot leg of a split-phase system, the neutral leg of another branch circuit, or it might even leak unto a de-energized part of another circuit (the switched leg going to a lamp or a circuit de-energized by opening its breaker). I think it was this thought that provoked the original author to speak of "ground fault" being something of a misnomer. And it's certainly true that the devices sense "balanced current" and not a "ground fault" in particular. Compare this with certain ungrounded systems (for example, railway traction motor circuits) where there ctually are devices that are purely sensitive to ground faults; any grounding of the ungrounded system trips the detectors and removes power. Such devices would be properly called GFCIs.

Atlant 11:55, 20 Jun 2005 (UTC)

Yes, and also in many renewable energy systems, some of them are wired up in a balanced way with neither of the two wires connected to ground, in which case, of course, there must be a breaker on both sides. In this case there is no ground, and no concept of ground fault. Thus what's really being measured and detected is a balance fault, i.e. basically what would be a violation of Kirchoff's current law, were it not for the unknown existence of some other leakage current somewhere else (not necessarily to or from ground). Also the concept of a balance fault nicely generalizes to three phase, where, for example, a three-phase BFI could trip if there was any imbalance of total current (i.e. if the total current didn't sum to exactly zero). Glogger 23:02, 30 December 2005 (UTC)

I have (re-?) inserted a brief explanation that GFCI is the usual name in the U.S. and Canada, which it certainly is, regardless of arguments as to whether the term is strictly defensible. On a related note, is "Balance Fault Interrupter" used anywhere? If it does appear in documentation or industry literature, a cite is in order; if it's new coinage proposed by a Wikipedia contributor, it really doesn't belong. Sharkford 19:27, 1 February 2006 (UTC)

Strictly speaking, a GFCI is different from a RCD in that a GFCI will trip in the presence of a neutral-earth fault (even though there is no voltage difference). It does this by having a second coil around the supply conductors (as well as the sensor coil). This provides a positive feedback loop when the neutral-earth circuit is made (ground-fault) and the GFCI trips. A RCD will not do this.--210.55.171.62 23:14, 17 October 2006 (UTC)

[edit] miswirings

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)

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)

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)

[edit] mixing mains and signal wiring in us

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)

Hubbell makes a variety of products that put ethernet, phone, and power into the same faceplate. Of course it's nicely designed to keep things separated by metal dividers. From an aesthetic and design point of view, it's fantastic, the way they got everything lined up, so when you install all the sockets you have "all your ducks in a row" so to speak. Glogger 23:07, 30 December 2005 (UTC)

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)

[edit] RCD vs RCCB

whilst the term RCCB is more descriptive it seems to have fallen out of favor at least here in the UK. Nearly every manufacturer and most standards and guides use the term RCD nowadays. Should we change the article to reflect this (if we do we should probablly also do a pagemove). Plugwash 01:51, 30 Mar 2005 (UTC)

My taste would be to:

Create a redirect from RCD to RCCB
Modify the lede of the article to mention the new term and how it is replacing the old term

But I don't feel strongly about this; if you'd rather move the article, flip all the references from RCCB to RCD, and add a bit to the lede describing the now-archaic ( :-) ) term RCCB, feel free! But don't forget to clean-up all the resulting double-redirects of RCCB that may exist out in Wikispace. (It's for this reason that I generally don't rush to rename an article whose name is still within the bounds of "accurate enough".)

I assume that the lede also mentions GFI, which is the universal, casual term in the United States. If it doesn't, I'll edit it in right now. (It's okay; GFI and GFCI are both there in the second 'graph.)

Atlant 12:16, 30 Mar 2005 (UTC)

[edit] Arc-Fault Interrupter

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)

Aha! I found the pre-existing article and linked it as a "See also".

Atlant 19:03, 30 Mar 2005 (UTC)

[edit] How do RCDs actually trip?

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)

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)

Thanks! Atlant 23:22, 3 Jun 2005 (UTC)

[edit] Leakage limits: real safety or imaginary?

"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)

Safety limits are not really what its about. A typical example that shows this is a damaged immersion heater. It is very common for the element casings to split open allowing electrical power to flow directly through the hot water. This is a normal part of the life cycle of an immersion heater. This will trip any RCD immediately, although (counterintuitively for those without much electical knowledge) there is no danger, ie people are not getting electrocuted because of it. RCDs tripping due to split elements of fixed appliances does not in reality give any added safety, thus is more correctly described as a nuisance trip. I realise this may sound counterintuitive, but bear in mind safety is removal of danger, and danger equals number of deaths, and split immersion elements are simply a non issue from a safety POV. They arent electrocuting anyone.

How is the 30mA figure reached? It is primarily a question of what will generally stay working. Anything more sensitive will be troublesome, 30mA is mostly ok... though not always. Some installs are horrors from the point of ongoing nuisance trips.

I hope RCDs turn out to reduce deaths, I really do. But... the usual wondrous descriptions of them are I fear significantly inaccurate.

Tabby 21:46, 8 Aug 2005 (UTC)

If you have water energized by an exposed heating element in an immersion heater, and it is in an ungrounded metal container, like grandma's old Maytag washer out on the back porch, or a bucket, and you happen to touch the bucket and a faucet, you will get a painful or dangerous shock. (been there, done that). It is basically no different from the numerous deaths which resulted from someone in a bathtub being electrocuted by a plugged in appliance which fell into the tub. Edison 22:36, 15 March 2007 (UTC)

[edit] Are they really safer?

The article says RCDs increase safety: to be honest we have yet to see. Although they offer protection against known issues, they also introduce a number of dangers.

Firstly users often take full advantage of the protection they offer, using equipment they would never dare before they got their RCD. Examples often seen are plugging wet electrical goods in, using power tools outdoors in the rain, using or installing goods that are known to be problematic safetywise, on the basis the RCD will protect them, and so on.

Also RCDs will kill lighting ciruits quickly in a fire, due to smoke and carbon caused leakage, and deaths are known to have occurred because of this. I curently recommend it is best not to put lighting on an RCD, except with TT installs where they are necessary for basic safety.

Also users tend to believe RCDs will proetct them against risks they dont, and become over confident as a result, exposing themselves to danger. A classic example is that of fitting an RCD plug to an electric drill, in the belief that the power will be cut if they drill into a live wire. In reality no such protection is given by this arangement. First the RCD only detects current imbalance _in the drill's supply_, so it wont even notice the user getting fried, as the shock current is coming from the wire buried in the wall. Second, if by some miracle it did manage to receive a heavenly missive telling it Jo's getting fried, cutting power to the drill, which is all it can do, would make no difference, since the power to the drill case is coming from the wire in the wall, not the drill's own lead. The problem here is simply that the user thinks the RCD will protect them against drilling live cables, ceases worrying about it, and does things that are a threat to life.

I'm not taking an anti-RCD stand here, just being realistic enough to say that the safety benefits are not what is being widely claimed. Or even close.

Only time will tell where the balance lies between the hazards they create and the hazards they protect against. Lets just hope theyre the right move.

Tabby 21:46, 8 Aug 2005 (UTC)

[edit] RCDs and immersion heaters

Tabby writes:

I'm afraid you're not considering all the possibilities. Let's take, for example, my hot tub. It has this nice immersion heater that is in intimate contact with water that's just loaded with ions that make the water very conductive. When the immersion heater eventiually fails, the water is connected to the live windings of the immersion heater and becomes charged to some arbitrary voltage (depending on where the leak in the immersion heater occurs. Typically, they fail near the top end so in the US, you could almost count on the water being connected to a full 120 vac at the end of the split phase-wired immersion heater. (And if you don't believe me, I'll show you a heater that failed exactly as I'm describing!)

Now, step into my hot tub. Without an RCD, YOU probably form the lowest-impedance path from ground to the energized water. You've just used up all nine of your lives, Tabby. But with an RCD, the water conducts enough leakage current to the grounded pumps and such that the RCD trips and de-energizes the water.

The same sorts of situations can happen in houses with electric hot water heaters and one or more runs of plastic insulative piping. Without an RCD, you can get energized water (although the situation may be less severe than the hot tub because the poable water may contain fewer conductive ions). (By the way, are you familiar with the fact that hot water heaters usually install dielectric joints in the copper piping? So even with copper piping, it's not impossible that the copper somewhere in the house won't be well-grounded.)

RCDs save lives, and properly designed RCD circuits typically don't put emergency egress lighting on the same RCD device (or even any RCD device) as the circuits that pose shock hazards.

Atlant 00:16, 9 August 2005 (UTC)

[edit] How to Evaluate Risk

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)

[edit] Re RCDs saving lives

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)

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)

[edit] What is the "residual" in RCD?

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)

[edit] How does earth leakage circuit breaker differs from residual current circuit breaker

IMO it doesnt--Light current 23:48, 23 April 2006 (UTC)

ELCBs don't measure current imbalance, instead they measure current in the earth wire. This gives them much less shock protection. Tabby (talk) 23:06, 7 December 2007 (UTC)

[edit] Disadvantages of RCDs?

I understand from the comments above why RCDs shouldn't be used in lighting. Why are they not used everywhere else? I suppose they cost slightly more and that the differential transformer uses up some extra energy. Are there other downsides? --Stereo 12:42, 6 April 2006 (UTC)

Nuisance tripping!--Light current 23:52, 23 April 2006 (UTC)

Nearly all appliances leak some current to earth and this can seriously add up. For this reason and due to the huge disruption of a trip covering a lot of equipment its inadvisable to put too much kit on the same RCD. However RCDs suitable for fixed installation are still quite expensive (it's a chicken and egg thing, RCDs suitable for fixed wiring won't get cheaper until more people use them and more people won't use them until they get cheaper) so the typical home (at least here in the uk) ends up with a split load board (some circuits only on the main switch the rest all on a single RCD). So a comprimise ends up being made between the desire to have RCD protection and the desire not to load too much on that one RCD. Plugwash 14:23, 5 May 2006 (UTC)

Because of the existence of the combination RCD/duplex-outlet, current American practice seems to be tending towards lots of RCDs protecting individual portions of branch circuits. So, for example, in my house, I have the following RCDs:

One in the garage, protecting all four garage outlets and one associated exterior outlet
One in one bathroom, protecting just that bathroom
One in another bathroom, protecting that bathroom and two others
One protecting a portion of the basement workrooms, the central vac, and two exterior outlets
One protecting one exterior outlet
Three protecting kitchen convenience outlets.
One serving the kitchen garbage disposal
One serving the dishwasher

With this arrangement, nuisance tripping is minized as is the scope of the failure if an RCD trips. With the exception of one kitchen appliance that trips one RCD (which is apparently sensitive to induced noise; there's no ground fault in the appliance.), we hardly ever see a nuisance trip although we've seen some genuine trips.

Atlant 15:25, 5 May 2006 (UTC)

Yeah you can get RCD outlets in the UK too but unlike your american ones they only protect thier own outlets. Also they are pretty expensive. Plugwash 17:32, 5 May 2006 (UTC)

Here, the going price is about US$12-$13, and they're frequently put "on sale" at $10 or so.

Atlant 19:17, 5 May 2006 (UTC)

about £20 in UK, which is ~$40 a pop, in a slightly less wealthy country than US. And they don't daisy chain, one rcd socket only protects itself. Tabby (talk) 23:08, 7 December 2007 (UTC)

[edit] RCD's and MEN connections

What are the implications of using RCD protection where MEN connections are present?

What are MEN conns? Is it the same as PME Protective_multiple_earthing (protective multiple earthing in UK?)--Light current 08:36, 5 May 2006 (UTC)

Assuming you mean a neutral thats tied to real earth at multiple points and/or used as a protective conductor as well as a neutral there are two reasons why a RCD shouldn't be used in such a core.

Paralell paths bypassing the RCD will cause it to trip when it shouldn't
Isolating a combined neutral and earth core is a BAD idea.

However its perfectly fine to feed a RCD from such a system provided neutral and earth remain seperate after the RCD and the only path from the outgoing neutral to the transformer neutral is to go through the RCD. Plugwash 09:09, 5 May 2006 (UTC)

[edit] alternative names for the device

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

[edit] Category: Electrical safety

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)

[edit] Surge protector into RCD

Forgive my ignorance, but what's the typical result of plugging a surge protector into a RCD? Will both still function correctly? Nullbit 01:02, 25 September 2006 (UTC)

Yes it will Blaab

Thanks Nullbit

[edit] RCDs in Australia

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)

[edit] Cups of Rice?

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)

[edit] Rename article to more commonly used term Ground fault circuit interrupter

I wonder if more of these devices are in use in the UK or in the US? What are they called in other English speaking countries? We should title the article with whatever is the more common term. Checking Google, I see for "ground fault interrupter" 96,100 hits, for "ground fault circuit interrupter" 167,000 hits, and for "Residual-current device" only 67,300 which reduces to 65,000 when Wikipedia and its mirror sites are removed. I propose renaming the article to "Ground fault circuit interrupter" unless there is a good reason to use the present term. Edison 22:30, 15 March 2007 (UTC)

Residual current devices are called as such in New Zealand, and presumably, Australia as well because we routinely purchase each other country's brands for such devices. --JNZ 21:21, 19 July 2007 (UTC)

Object Tabby (talk) 23:09, 7 December 2007 (UTC)

A GFI is a different device to an RCD. It has a second coil attached to the main sensor coil around the supply conductors. This enables a GFI to detect and trip on detecting a neutral (grounded wire)-to-earth fault. GFIs are covered by a different standard (UL943) which incorporate tests for the neutral-to-earth fault. Strictly speaking, there should be a separate entry on GFIs. --Kiwigpz (talk) 09:45, 27 December 2007 (UTC)

Do you have a ref for what standard RCDs are covered by in that same set of standards? And for the different arrangement of current sensing coils? GFI and RCD seem to be the same thing. Edison (talk) 06:15, 28 December 2007 (UTC)

There are no US, Canadian or Mexican standards that I know of for RCDs, only GFIs - I stand to be corrected on that as I have worked only on GFCIs for the US market. Internationally for RCDs, there is IEC61540 http://webstore.iec.ch/webstore/webstore.nsf/artnum/023695?opendocument, IEC61008 http://webstore.iec.ch/webstore/webstore.nsf/artnum/036223?opendocument, and IEC60755 http://webstore.iec.ch/webstore/webstore.nsf/artnum/034162?opendocument. Australia and NZ use AS/NZS3190 http://www.saiglobal.com/shop/Script/Details.asp?DocN=AS037588948321 as well as local adoptions of IEC 61008. The UK uses BS 7288 and BS 7071. All these standards refer to RCDs - not GFIs. It's interesting to note that 120V countries seem to use GFIs and never RCDs and 230V countries use RCDs and never GFIs - don't know why. If you follow this link http://www.fairchildsemi.com/ds/RV%2FRV4145A.pdf to the datasheet for the chip that is used by most electronic GFIs and RCDs (my opinion) you will see on page 4 a nice description of the differences in the circuit to give the different operation. Figures 2 & 3 show the standard circuits - you will see two coils in the GFI and one in the RCD.--Kiwigpz (talk) 10:23, 28 December 2007 (UTC)

I am trying to determin if the RCD and GFI are really different devices, or if it is just regional terminology difference. This afects how the article should be set up, or if there should be two articles. The standards referred to by Kiwigpz are only viewable in a preview format without paying a large sum, so the test standards are not viewable to determine the trip and nontrip conditions the RCD and GFI must satisfy. The chip data sheet shows first a circuit for a 2 wire ungrounded outlet which would trip if the neutral and phase currents differ sufficiently, as would be the case for a phase to ground leak, or a leak to the protected circuit's neutral from a different source (less of a concern). The arrangement for a three wire grounded outlet apparently provides for tripping if there is a low resistance connection between the neutral and the ground prongs of the outlet. Are you saying that the first trip condition is also characteristic of a RCD but it lacks the second trip condition? I am looking for the trip/notrip conditions for the two devices (if they are in fact different). Edison (talk) 17:31, 28 December 2007 (UTC)

Yes, to my knowledge, no RCD will trip on a neutral-to-earth fault. Sorry but I have no other references to back that up - just the standards listed. UL943 contains the test for the neutral-to-earth fault that GFCIs will pass, none of the RCD standards do. I will try to find a reference that confirms that.--Kiwigpz (talk) 09:52, 29 December 2007 (UTC)

[edit] Trip without load attached

What would cause a RCD to trip without a load (or an ungrounded load such as a cell phone charger) attached? --D3matt 03:42, 23 March 2007 (UTC)

Well, the obvious cause would be something bumping the "test" button. Older units (of the 1970's ) frequently tripped when there was a lightning storm, and today's might also if a sufficient spike of voltage affected the amplifier circuit which monitors the residual current. A power quality problem in the building could also cause spikes in the supply voltage which might afect a unit. Then there is the possibility of one simply being defective or too sensitive. Or the ungrounded load could conceivably have had a short to some nearby ground, or an extension cord or adaptor could have leaked current to ground. It does not take much current. Edison 15:30, 23 March 2007 (UTC)

[edit] Trip on cooker circuit

I have a current fault of a cooker that trips my RCD. The trip may not come immediately on turning the cooker supply on but it will normally trip after a given amount of time. For example the trip may occur when I turn the oven on or after a few minutes with no action or change occuring (no load change). Another example was when the cooker was on for 59 minutes and I went to take a shower. As soon as I switched the electrical shower on the trip occurred.

This RCD unit is on all of the house supply (separate breakers obviously)and none of the circuits are split. I have recently installed new electrical circuits in the kitchen but the cooker circuit was only modifed (change of position). I cannot work out if...

1. The cooker is faulty (has been in the garage not used for 3 years).

2. The wiring is faulty or there is another faulty circuit somewhere.

3. The RCD trip device is faulty (i.e. over sensitive).

The RCD has some history of nuisance tripping and previously with the original electric cooker it used to trip if sometimes if both ovens were used or if the cooker was not used for a week or so (like returning from holiday).

I could bypass the RCD but I would lose all protection for all circuits.

I hesitate in bypassing a safety device.

Are RCDs suitable for cookers?

A.Wheeler 10th Sept 07. —Preceding unsigned comment added by 194.133.59.125 (talk) 12:03, 11 September 2007 (UTC)

http://www.wiki.diyfaq.org.uk/index.php?title=RCD Tabby (talk) 23:27, 7 December 2007 (UTC)

No liability is assumed by providing the following comments. Help out your friends across the pond with terminology: the "cooker" is the kitchen range, with burners on top and an oven, yes? Is it powered by 240 volts, with two wires, or 240 volts plus a neutral to operate the controls on 120 v? The requirements for whether the range requires a GFI (ground fault interrupter, or RCD if you prefer) will depend on your applicable electrical code. Outlets in the kitchen generally (in the US) are required to be on ground fault protection because of the presence of the sink, of moisture, and of grounded metal appliances. Here the range is often on a separate circuit from the outlets, and I have certainly seen installations by electricians which were approved by inspectors where the range was not on a RCD. But if it has a convenience outlet as part of it, then that should be on a RCD. It would be appropriate to have a licensed electrician check it out. Safety from shocks is important. At least 3 things are possible: 1) The cooker could certainly have some part of the wiring which at times shorts to the grounded metal part of the appliance, tripping the RCD. This could be part of the heating element, or ebven the clock, RCDs are generally built to trip in milliseconds on milliamps of such leakage current, not like an overload protection device (fuse or breaker) with a long time curve, which might trip on a moderate overload after several minutes. 2) A gadget like an RCD can trip falsely. They make millions of them, and a few are bound to be defective. 3) Something else could be on the same circuit as the cooker which is tripping the RCD. Isolate other appliances. You mentioned the "electrical shower." Is that a demand heater near the shower which runs when hot water is needed, as opposed to a storage heater in a utility area? Is it on the same circuit as the oven? Are you overloading a breaker? Edison (talk) 23:43, 7 December 2007 (UTC)

The original poster appears to be in the UK both from a whois on his IP and from the terminology he uses. I will make that assumption in my reply.

First of all I will answer edisons questions and clear up some differences between UK and american practice

Domestic properties in the UK normally use 240V single ended single phase. Some larger houses and most commercial properties get 240V/415V three phase. 120V is only used in specialist situations.

Cooker generally reffers to a device with both oven and hob (probablly what you reffer to as burners but we tend to reseve the term burner for things that actually burn ;) ) integrated into a single unit though it can also sometimes be used to reffer to a seperate oven or hob.

Afaict american "GFCI breakers" combine the functions of leakage detection and overcurrent protection. We have such devices (we call them RCBOs) but they are expensive and not normally used in domestic installations. More common here is to have a single RCD (which only provides earth fault protection) covering either the entire installation (RCD incomer) or all the circuits that are to be RCD protected (known as a split load arrangement) then seperate MCBs (overcurrent breakers) for the individual circuits.

An electric shower is a unit fixed on the wall in a shower cubical or above a bath that takes cold water in, heats it and lets it out through a shower head. Controls on the front of the electric shower allow the user to turn the water on and off and have some control over flow and power (which indirectly control temperature).

It sounds like his electric shower is on a seperate MCB but on the same RCD as everything else.

Now back to the orginal posters problem

Cookers are prone to becoming leaky devices and it is not that unusual for them to trip RCDs, most electricians therefore prefer to keep them on NON-rcd circuits. However if there is a socket on the cooker circuit and this socket could be "reasonablly expected to supply equipment outside the equipotential zone (interepretations of this reg vary widely) then it either needs to stay on RCD or the socket needs to be removed.

Bypassing the RCD for the whole installation is not a good idea. Really you need the help of an electrican who knows what they are doing and has proper test equipment (no a multimeter is not much use here sorry) to test the RCD and the cooker and the wiring and any other suspect appliances and decide where to go from there.

-- Plugwash (talk) 00:40, 8 December 2007 (UTC)

[edit] Lightning

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)