How to explain what a RCD does to your average layperson? - Page 1
Forum section: electronics / projects

author: david77
author_rank: Frequent Contributor
timestamp: March 03, 2015, 03:05:01 am
content: For some reason I have to explain to parts of my wider family why installing a RCD is a good idea. I've tried it but have so far failed, nothing but blank stares all round.I think I fail because the simplest concepts (like voltage and current) are absolutely alien to them.I'm having the idea of building a model. Isolation transformer, RCD, MCB, puppet with a bulb as head, bucket of water, some wires. Make up my own isolated TNC and TNC-S grid for demonstration purposes.The problem is there's an old house with electrics from 1954. No RCD, no PE connection, and worse. And some of my dear family have got it into their heads that that house has to be rented out.Apparently there is no law in Germany that stops you from doing that. The electrics are deemed ok as long as nothing is changed. Ridiculous - no dangerous!Any ideas?At least they agreed to have a licenced electrician come round to do a check up - I'll be there and I hope he can sort them out.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 03, 2015, 03:28:44 am
content: You can begin by explaining it to us, I've never heard of an RCD.

author: Lightages
author_rank: Unknown
timestamp: March 03, 2015, 03:34:37 am
content: An RCD (Residential Current Device) is the same as a GFCI (Ground Fault Circuit Interupter) in Canada. It is a device in the electrical panel or in the wall socket that detects an imbalance in the current flowing through the live and neutral conductors and breaks the circuit if the differential current rises above a certain value, usually 20mA, some 30mA and some are rated for 10mA. This differential current flow is an indication that at least some of the current flowing is flowing outside of the normal safe path, a human to ground for example, and therefore is supposed to save the human's life by cutting the current.In Canada, most of at least, they are required for any circuit that is near a water source, bathrooms, kitchens, outside wall sockets, etc. At least that was what I remember before I left.In Chile, they are required on any circuit that has a wall socket. They are not required on circuits dedicated to lighting only.

author: Siwastaja
author_rank: Super Contributor
timestamp: March 03, 2015, 03:35:08 am
content: Why would you need to get so technical about it? It's not enough if you tell them it's a REAL lifesaver, and required by the new building codes for a very good reason? You can quote me: someone on the internets says it saved his life. It really did once.Anyhow, if you need to get technical, try this: Explain that electricity runs between two wires, and if you get between these two, you'll get electrocuted, but it's quite improbable that it happens that way, with the actual two wires. But now explain that the "another wire" is not actually only a wire, but it is connected EVERYWHERE, literally in the ground, pipes, floors, etc., so you only need one exposed wire (the another one) somewhere to die. Now explain that the RCD is a high-tech device which automatically detects anyone being between "the wire" and "the everywhere" and cuts the electricity so quickly that you'll get shocked, but won't die. RCD brings us back to the situation where you need the actual two wires to die, which, again, doesn't happen that often.If this does not help, do what you need to do. Potentially killing people with negligence is no joke, and not a matter of family politics.Or, show them this thread after a few more replies. Safety is no joke; there is a reason why people don't die of electrocution all the time anymore. RCD is one of the best things to happen to safety because the effect is great and price is low - it may be the single most easy and still effective fix.1950's electrical installations may require a large checkup anyway. RCD may not be the only thing required. An electrical fire may result in from loose connections or poor insulation in 60-year-old installation.

author: AG6QR
author_rank: Frequent Contributor
timestamp: March 03, 2015, 03:35:49 am
content: An RCD is usually called a GFCI on this side of the pond.But whatever you call it, it's a device that watches to see if all of the current that goes out on one wire, also comes back on the other wire. If any electricity escapes and leaks out to ground by an alternate route, it shuts off the electricity. In this way, it greatly reduces the danger of electric shock. If a person were to touch a hot wire while touching a plumbing pipe or other ground, the electricity will be shut off before the person can suffer injury.The above is a fairly plain language explanation for a layperson who doesn't understand much about electricity. It's simplified, but I believe not so much as to be grossly misleading.

author: coppice
author_rank: Super Contributor
timestamp: March 03, 2015, 03:43:57 am
content: Most people have touched the mains at some time and know it hurts. They also know that if you don't get clear quickly it can kill. You just need to tell them than an RCD/GFCI is like Darth Vader. It can feel your presence, and it will disconnect the power fast enough that all you are likely to feel is an initial jolt.

author: EEVblog
author_rank: Unknown
timestamp: March 03, 2015, 03:54:29 am
content: Forget technical details, just tell them it will stop them getting electrocuted. Anyone who can't understand that probably shouldn't be allowed to have one!

author: PeterFW
author_rank: Frequent Contributor
timestamp: March 03, 2015, 03:56:30 am
content: Quote from: coppice on March 03, 2015, 03:43:57 amIndeed, tell them it is a faster fuse.The normal fuse will not trip fast enough to keep you from dying.The RCD, FI, GFCI, Schutzschalter or whatever you want to call it will work much faster to increase your chance to survice in case of a broken wire inside the toaster.Or water seeping into the outlet in the kitchen/bathroom, faulty wire in the dishwasher and so forth.But beratungsresistente and merkbefreite will not want to hear that.I tried to tell my folks to change the incandecent lighting to CFL, i crunched the numbers and explained it to them in baby talk.No chance!I broke down and replaced the fixtures out of my own pocket on one floor.Right after they got the next invoice from the power company they replaced every bulb in the house with the "Dumme Energiesparlampen die eh nach ner Woche kaputt sind, das haben wir vor 20 Jahren schon ausprobiert, die taugen nichts."

author: david77
author_rank: Frequent Contributor
timestamp: March 03, 2015, 04:31:12 am
content: Quote from: PeterFW on March 03, 2015, 03:56:30 amSo true. I tried arguments like "...might save lives..." and all that. What did I hear back from my mum: "Then granddad would have to be dead, too."I'm so glad I had her flat updated with a RCD without her even knowing about it some years ago.@all:Probably you're right and I'm thinking to technical. But whatever I've told them so far they don't seem to want to listen.Problem is, apparently there is no rule or law against renting out a house with wiring that was up to VDE standards (VDE publishes the electrical code in Germany) when it was built but isn't anymore. That's what the landlords association told me.I wouldn't have much of an issue with it if the house was for one of my relatives personal use, but letting it to some unsuspecting bastard who might kill himself in it is too much.I now hope for the sparky to find plenty that's wrong later this week.

author: pickle9000
author_rank: Super Contributor
timestamp: March 03, 2015, 04:57:08 am
content: I don't try to explain it I say:A circuit breaker is to protect property (from fire or whatever), a GFCI is a breaker that protects people (from death). I also state that nothing is perfect but well worth it.

author: Psi
author_rank: Super Contributor
timestamp: March 03, 2015, 06:03:24 am
content: Maybe say something like this...(its wrong but easy to understand to a non technical person)Electricity is supposed to go from the wall socket through the positive wire to the appliance then return to the wall socket on the negative wire.An RCD is continuously looking at this 'in' verses 'out'. It instantly knows if electricity is going somewhere else, like through your body and into the ground, and it turns off the power quick enough so you don't die.It's like a tiny robot that unplugs the appliance the splitsecond you get an electric shock.

author: IanB
author_rank: Super Contributor
timestamp: March 03, 2015, 06:23:11 am
content: Not wanting to be controversial here, but one should make a balanced assessment of risk before being worried. Will RCDs when widely installed prevent some people from being electrocuted? Yes. Will the absence of an RCD in your home make a significant difference to the probability of you or people near to you being electrocuted? No.You have to consider the probability of you suffering death by electrocution over an average lifetime in a reasonably normal and well maintained home. You can estimate this probability by the number of times you have experienced an electric shock from the mains. The probability of dying is less than the probability of receiving a shock. If you have never received a shock in, say, 20, 30 or 40 years, then the probability of receiving a shock on any given day is less than 1 in 40 x 365, say 1 in 15000. Since most people who get shocked don't die, the probability of death from electrocution is much smaller than that.If you weigh up those probabilities, the probability that you will avoid a premature death by having an RCD is vanishingly small. So if you don't have an RCD or GFCI installed, there is no need to be paranoid. Install one for peace of mind by all means, but don't feel like your house is a death trap without one.

author: SeanB
author_rank: Super Contributor
timestamp: March 03, 2015, 08:12:19 pm
content: Just tell them that if they do not have it installed and working then if a tenant has a shock ( however slight) from electric wiring then they can sue you for damages and trauma. If they die you as the owner can go to jail or be forced to pay the surviving family of the person a pension for life. Nothing they put in a rental agreement can prevent this, as then the house is deemed to have been deliberately left unsafe.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 04, 2015, 12:53:56 am
content: Quote from: IanB on March 03, 2015, 06:23:11 amGod forbid! A rational argument in a safety discussion.I don't know what German liability law is, but that will aid in determining the financial value in doing this. Something else will be involved in peace of mind. You can look up electrocution statistics. Statistics from before about 1970 should approximate the probability of electrocution without the RCD. Your knowledge of German liability law should let you guess at the cost of a "preventable" electrocution. That, and the cost of the RCD will let you compare the expected costs of installing an RCD with the expected cost of not installing it. Those statistics will also give you some insight into whether you are morally comfortable with not installing one.

author: Siwastaja
author_rank: Super Contributor
timestamp: March 04, 2015, 04:43:44 am
content: I guess the number of deaths by electrocution of "normal people" (not counting professional accidents of electricians) has gone down by factor of about 100 in last 50 years or so. In the Good Old Times, it was considered somewhat a "normal" (although rare) accident to die as a result of an electric shock; something inevitable that can happen. Of course it wasn't common at all; but stilla thing. Nowadays, with much better building codes regarding electrical installations (RCD's being the single biggest contributor, no doubt!), normal people just don't die of electrocution anymore; it's so rare that it basically doesn't happen. And hasn't happened in about two decades now. (Utility workers and other professionals may still die every now and then.)So, the consequence is that "normal people" do not understand the risk of dying in electric shock anymore, because it doesn't happen. This is the same mental mechanism as in the anti-vaccination bullshit; people don't have measles anymore, so they don't know what it is.This 1950's house just represents the risks of its era.Ian is still completely right; even in the days when electrocution was "normal", it was very rare. People still took action to prevent it,because it was so damn easy to do so. That's why RCDs are required in new installations - they are dirt cheap - up that $10000 total electrician bill to $10100 and save a few lives a year? Great deal! But fixing old installations? Maybe. You decide. The risk is small enough that you are notrequiredto do so - because the cost of fixing old installation is orders of magnitude higher than just doing the new installations right.But the peace of mind should not be dismissed; it's important that you can sleep well. An RCD is money well spent in this regard, because it's no placebo. So if nothing else, make your family do itfor you, for your peace of mind.

author: gildasd
author_rank: Frequent Contributor
timestamp: March 04, 2015, 07:24:04 am
content: A European house from that era is only earthed in the kitchen at best.So replacing duces for differentials is a matter of simple safety in case a wire comes lose in an old appliance or touches the plumbing.That last one happened to me and blew a paint scraper out of my hand.

author: dom0
author_rank: Super Contributor
timestamp: March 04, 2015, 10:10:43 am
content: Quote from: Siwastaja on March 03, 2015, 03:35:08 amMake it twoOh, and about that "but we already got plenty of fuses" argument:Well, normal fuses or circuit breakers are not there to protect people. They're there to keep your house from burning down.