Residual Current Devices (RCD) - How they work

[@peterstiles1]

This is what you get when someone who really understands what he's talking about makes video explanations: great videos. Thanks.

[@eamongomaa4364]

Excellent explanation - finally someone not faking it, but actually knows what they are talking about. Thank you ever so much

[@davidprice2861]

Great to listen to an expert who speaks clearly with correct pronunciation. (very refreshing). Thanks JW.

[@tommcneil8752]

Thank you again john. I was hoping you would do a little more on 3phase RCDs , explaining the principle with a 3 phase only type and the ones with 3phase and neutral supply. It is always a pleasure to watch your videos.

[@garrygemmell5676]

Wish I had an electronics teacher like your good self when I was at school and I wouldnt have left with half the knowledge I needed and had to learn it again by myself later in life! Always very interesting and informative videos!

[@wayneharrison9222]

Just stumbled across this video while I have been trying to figure out my intermittent RCD tripping. It has helped enormously, thank you.

[@doc-holiday]

Hi John. Thanks for that great explanation on how RCD works. Your tutorials are so clear and simple to understand. On a different note i would have also mentioned that RCD do have their disadvantage in that if for example the neutral wire was cut then the device would be rendered useless in operation and if someone was to touch the active to earth then they would receive a severe electrical shock. The unit would not cut out.....! Just something i would have mentioned in your video. Keep up the good work. Cheers

[@doc-holiday]

@Walter Hess No the circuit breaker wouldn't trip. You would fry just like an electric kettle jug element heating you like a natural lamp and toasting you red raw.

[@mauriceupton1474]

The multiple earth neutral system is only used on land and small boats. In heavy marine applications they don't use the ships hull as an earth return because in marine applications that would cause a circuit breaker to trip and the electrical equipment to shutdown if one side shorted to the hull, also they do not want the hull to be a return path for electricity because it would cause metal electrolysis when shore power connections are made. 

[@parlenkow]

Yes I worked in crude oil tanquers an container ship vessels and there are not neutral in that's systems

[@myturkishlife1777]

This guy should be on the TV reading the news :-) Great explanation....

[@SqwarkParrotSpittingFeathers]

Thank you John, all your posts are informative and well presented.

[@gjbspark]

excellent series of video's... passed them to my apprentice saves me time thanks

[@BenjaminGoose]

Thanks for making these videos, I'm finding them very informative!

[@allanclarke5919]

Brilliant, thorough and clear explanations in all the Vid's. Thank you JW.

[@Angeloflight444]

Thank you so much for this! Clear and concise! Be well, be blessed.

[@graethom]

Thank you! Nice clear explanation with diagrams for us visual learners! Much appreciated!

[@parkeerwacht]

In offices here, we use what we call "alamats" Which is the same thing as a RCBO it is a breaker with RCD included. Even some household installations use these.

[@johnsamu]

Thanks for another extremely good explanation, I learned a lot today.

[@NAVPCRESTORE]

thank great explanation. i couldn't explain it better myself

[@SteveMayne1]

Thank you John, have always wondered how RCB worked, and have first hand experience a few weeks ago where the newly installed consumer unit RCD tripped due to 'rain water ingress' into a light switch. I dread to think what should have happened to us or to our home if we hadn't had the CU upgraded. Than you for the clear and concise explanation.

[@JwiseTheRealist]

Reminds me of Kirchoffs Current Law ... the good ol' days of electronic engineering and electrical principles

[@desacatadosfm6700]

Hi! Greeting from Argentina. In my country we know it as "Interruptor diferencial" or "differential switch".Excelent video!!!

[@BjornV78]

18:29 Residual Current Monitor or also called Line Isolation Monitor (LIM) . Those devices have also a earth connection (earth is not connected to the installation behind this device) and is only used for measure the impedance between each Live conductor (Phase or L1,L2,L3) and earth, and between Neutral and earth. In short, this device acts like a Ohmmeter, but on a live circuit.

[@danieladdyman9015]

Excellent!, I love the clear and comprehensive instruction in all your videos JW. Makes a refreshing change from the yadder on voluminously in the hope something remotely accurate is transmitted. Thank you.

[@AhmedJendeya]

Thanks Sir for this great video. In fact, I know briefly the idea of work of the RCDs long time ago, but what brings me here is the confusion I am facing now and searching for an appropriate interpretation for. The problem is that the RCD is supposed to sense the current returned from the neutral but the question is: what about the current consumed in the load? I mean, if the supply gives 2 amps and the load consumed 1 amps and converted it into heat or light .. whatever, should not I have only 1 amps returned current? Also, I know from the university days that the neutral carries current only in case of unbalance. Of course the single phase distribution for homes out of the 3-phase source will ensure that there is a permanent unbalance in the system, but what I remember is that the neutral will return only the unbalance difference. Finally, I would appreciate if you have experience in Operation Rooms safety and how the system of earthing to the PVC and the isolating transformers are related together. Regards,

[@PhilReynoldsLondonGeek]

Had RCDs in four of the places where I've lived - there was just one, not on the lighting or heating circuits, in one place, another I think was the same. The next, none at all until the new shower was fitted and then only on the shower circuit. Two where I am now, with the lights and sockets being on different ones. My grandparents' house that they lived in for years had one fitted on a rewire in the 1980s - it frequently (but not always) tripped when my grandmother switched off the combination oven's socket, seemingly only if the oven was still warm, and it was "whole system" so it frequently meant a trip to the cupboard under the stairs in total darkness. Had they stayed there much longer I might have investigated - I suspect the socket was to blame as the same fault did not occur after they moved.

[@parlenkow]

Wonderful explanation sir!!!! Thanks for share this information about residual current devices also known in us as GFCI

[@GadgetAddict]

How about countries like the Philippines where sockets don't have a ground and the neutral/live can be on either pin, depending on which way you plug a two-prong lead into the wall? Can you still use these kind of plug-in RCD devices and get the same kind of safety? In another comment, you say an RCD can't work without a reference to ground but other sources online suggest it will still work.

[@jwflame]

Gadget Addict The RCD will still work, it does not require a ground connection at the socket. It just detects an imbalance between line and neutral caused by a fault to ground. RCDs do require that the supply is referenced to ground, however virtually all electrical supplies are, usually at the transformer. An RCD will not work on an isolated supply as there is no path for current to return via the ground - however in that case the RCD would not be needed as there would be no shock risk from a person touching either line or neutral. Isolated supplies are rare, typically from some types of small portable generator or inverter.

[@GadgetAddict]

***** Great, thanks for the reply John. I'm renting so swapping out the breakers or running new wires isn't all that practical. But replacing the sockets or buying plug-in RCD devices are :)

[@LandersWorkshop]

Well said and good video. I have a generator that puts out 6500 watts, should this be grounded? I run power tools and charge my battery up using it...

[@BenGromicko]

Thank you, John. We just performed a few home inspections in Greece. And we came across these RCDs. And we wanted the information you just provided. Where can we find information about location requirements for RCDs? For the U.S., we refer to the International Residential Code and the National Electric Code.

[@robertwilson1434]

John That was very interesting and informative video. I wonder if you could produce video on RCBO use and operation. Thank you for all the hard work producing these video I have enjoyed watching them.

[@vinnie7020]

i wish i found your channel and videos earlier amazing mate youve done a great job could you do a video explaining the breakers relationship to circuits and cable calculations and power factor ratios difference in three phases ad single and motors etc please much appreciated

[@ugurozyar2032]

Great explanation! Thank you!

[@philcuore]

Thanks for sharing RCD, now i really know what it does.

[@Chrisipable]

Useful and easy understanding, you are so great.

[@anandakrishnan9462]

Hi JW, Where is the practical use of RCDs having I∆n=0.3A / 300mA. Does it gives protection against electric shock.? Should it can be used for residential applications.?

[@Mainly_Electrical]

Protection against fire

[@beckycgonzales7055]

You helped me today John. Thanks.

[@elijahsmith8567]

yes i design all parts for people to look at the many things what i have done. so i can learn you of things what i can do. so listing to the story are giving.

[@ahmedbighouse2949]

respect to your effort sr.

[@Cruner62]

Hi John, I thought I understood how most protective devices operate and you have confirmed with your excellent presentation that I actually did, however, my thinking became skewed when reading some posts on a particular site. First I believed that an RCD was complimentary to a good Earth system. I was aggressively informed that RCDs did not need a good earth to operate safely so if there was faulty earth you would still be safe. I understand the differences in the systems you elegantly described, however, so called electricians on the site did not answer my question which was:- If there is no earth present at say an appliance and a fault occurred how would the RCD detect an imbalance if there was no path to an earth. I assumed the path would soon become a apparent when a person touched the the appliance then the RCD would trip on contact if other things were in place of course. However, from experienced this 30ma used to trip it gives quite a jolt and from other sources I understand can result in problems for people with heart defects. What is your take on this?

[@jwflame]

+John W The imbalance occurs when someone or some other earthed object contacts a live part, current then flows through the person/object into the ground. This does mean the person may feel a shock, but the RCD will limit the shock to a very short duration. Although a 30mA RCD will trip at that level, it does not limit the current in any way, so it is entirely possible for the current to exceed that significantly, which may cause problems for some people. However disconnecting the supply quickly (less than 200ms for a typical RCD) dramatically reduces the possibility of injury or death. Having an RCD is still far better than not having one, particularly with the prevalence of double insulated appliances which do not have any earth connection.

[@Cruner62]

Thanks John I have been aware that 200ms exposure at 230v can cause heart fibrillation and affect pace makers in vulnerable people. I would never dream of using a system without a combination of the two and was startled by Electricians even suggesting RCDs could be regarded as safe without an Earth presence.

[@argentum3919]

Thanks, very informative. I've looked at my fuse box and noticed the bathroom wall fans are not on RCD, only my kitchen appliances are on RCD. That was very irresponsible of the electrician. I then checked the RCD test button and it does nothing. Time to call the electrician. The MCB/RCD combined switch you showed is a great solution for the bathroom fans, didn't know they existed. As a point of interest. If you test on live wire that is on RCD using a neon screw driver, such as in your other video, should that not trip the RCD switch since the human body will earth some of the current and hence will not return to the RCD unit thus causing an imbalance in current between the line and neutral?

[@copelandaa]

A very good question. A majority of RCDs have a fault current rating of 30mA. Now 30mA passing through your body is described in 17th Edition Wiring Regulations as "10-15mA: Muscular contraction, can't let go. 20-30mA: Impaired breathing". Etc etc. Now using Ohms law, from John's video, the resistor was measured at 1.535Megaohms (1535000ohms) and John was using 250VAC (or there about), so the simple maths is I=VR (250V / 1535000Ohms = 0.0001628A) or 0.16mA. 0.16mA is 'barely perceptible, no harmful effects' so an RCD would not trip in this instance, you'd need another 29.84mA for the RCD to trip. -Andrew

[@argentum3919]

copelandaa Thanks for that explanation and calculation. I forgot about the tolerance before it trips. But are you saying that the built in tolerance level is actually lethal if it doesn't trip?

[@jwflame]

chinacane 30mA can certainly kill someone, it depends on the exact circumstances. - and if someone contacts a live wire, the current can easily be more than 30mA even with the RCD - the current is determined by the impedance of the fault. The RCD only limits the duration of the shock, not the current.

[@app0the]

Awesome info as usual! I would like to ask if you could make a small video about properly grounding an outside TV antenna. DVB-T is making its way to the rural areas here and I would like to install one but without the risk of a housefire in case a thunderstorm hits it :) Many thanks in advance!

[@ssjktjessica6]

Hi J W , on the R C D ,there's a diagram on the face of it , it shows 4 poles with a broken line running through the middle, my question is how can you tell what side is the supply, and what side is the load? ,great video's ,I'm really enjoying, thanks Steve

[@dragonsrl]

great stuff

[@math-with-afshin]

Hello Sir , initially really I'm very thankful of you for your very helpful video series , you present your nice videos look alike "sport events tellers" and sometimes understanding your accent is a little bit hard for none natives and specially a challenge for me, anyway I love British accent and by listening you my English listening skills would be improved as well...LOL... , could you please answer these questions , on 4:54(time of video ) in the book we have RCD and RCBO , it seems that RCBO is better than RCD because RCBO does somehow operation and in this way "save life of people" and also protect the devices such as TV and washing machines and so on , yes ?? So what is the difference between RCD and RCBO?? which one of them for home is better and most suitable ? each ones RCBO for TV and washing machine is needed separately ? each one should has which specifications/ amperage ? each RCBO can cover how many devices ? sorry a lot of questions !! I am contacting from Kiev in Ukraine and by answering my questions you will solve a lot of problems for me and at the same time it is a very big favor, Your fan , your supporter , Afshin Heydari

[@biggib8]

great video john. dunno if u can help on installing into rcds , I wanna install new double socket & our rcd is right above the area I want the socket to be. is it matter of feeding new wires from the rcd to new socket down below? I can't spur off another socket becos the nearest one across the other side of the room.

[@michaelcostello6991]

Have you a video explaining how an RCD can be used where the earth looop impedance is too high. Is this an acceptable solution in a domestic situation where you do not want to install a larger cable etc etc etc Thanks

[@KurtisPape]

Ok, the scenario with the Generator with having no fault current to earth doesn't result in an electric shock, but the 1 thing I really want to know is with wall power, if you touch just the active and you are standing on concrete floor with rubber boots on, will there still be a current path to earth? Also the rest of body is isolated so your not touching neutral or an appliance etc.

[@jwflame]

In theory no shock - but in reality it's more complex. All depends on how effective those insulated boots actually are, which will also depend on moisture, humidity and so on. There is also capacitance to consider, as an insulating layer between a live part and earth forms a capacitor, and the other possibilities of someone in that situation accidently being in contact with something else.

[@KurtisPape]

@@jwflame Interesting... thanks for info. It's just because at work there have been a couple electric shocks, mine was I actually had twisted a live conductor with no shock and it wasn't until I earthed myself I got a boot. The next 1 was a worker stripped a door heater back and it was live, 1 finger was on the metal of pliers and he instantly got a boot and he was standing 1 meter away from any earth with electrical boots on. (the heater is rubber outer so it is not earthed) I know electric shocks should never happen, but its complicated when you know the circuit breaker, but somewhere along the repair the active accidentally gets put of a different circuit. Always gotta re-test...

[@ottohardwick5323]

John, on a related topic, what do you consider the best means of rigging a warning buzzer for when an RCBO trips? There's a possible water ingress in our garage circuit with the very heavy downpour a couple of days ago and it tripped but now appears stable. I would like to fit a warning device. What do you think of RCBOs with auxilary contacts in order to fit a buzzer/light? If I can actually find one, that is, as I can see it mentioned online but rather difficult to find...

[@jwflame]

Aux contacts are not likely to be available for domestic RCBOs or anything else intended for a domestic consumer unit. Probably easier to use something which detects the loss of electricity, a random example: www.instructables.com/Power-Failure-Alarm-for-Freezer/

[@ottohardwick5323]

@@jwflame indeed, it's just that I have an aversion to devices that sit there consuming energy - even if a tiny amount - when doing nothing 99.99% of the time! The idea of a switch physically connected to an RCBO is more appealing from that point of view. When I designed a one-shot/extendable timer for the pond-fill solenoid valve I deliberately did it with a zero standby current with some jiggery-pokery.

[@jayashpatel6165]

ok i got a interesting question. I have a rcd on my fuse box and then the manual said i should install a rcd spur socket for the electronic underfloor heating. which i realized later i don't need as fuse box has one. But what i dont understand why does the main fuse box rcd trip when i pressed the t button on the spur switch for underfloor heating. Also i have outdoor garden rcd sockets which work fine when i press the t button. Another issue i have is when i connect the yellow 110v transformer the rcd trips sometimes ?

[@johnlambert7470]

Very useful, thanks. But does the polarity matter - the hager and the British General (CUR63330A) are opposite ways round?

[@jwflame]

Depends on the manufacturer, some can be connected either way, others not.

[@PankajAgrawal-N]

You talked about imbalance tripping the RCB. So, with a 3 phase RCB trip if there are different loads on different phases (load imbalance), will it trip the RCB? Or, the zero sum rule is the real key and the RCB will trip ONLY when some current is leaked out to earth.

[@jwflame]

A 3 phase RCD has 4 connections, all 3 phases and neutral, so different loads on each phase still sum to zero.

[@abhisheksharma149]

What is the switching mechanism used ??

[@Nine-Signs]

Thank you for your videos, very useful.

[@grimfandingo4177]

In an off grid situation would I be able use an RCBO if I connected the neutral from the inverter to a ground?

[@jwflame]

+Grimfan dingo Yes, but before making such a connection check the inverter carefully, as some are already wired like that.

[@Dragon34th]

@ Brent Geery The reason why the trip current is so high in the UK? Well, I'm gonna be short. Mick Jagger. Welcome to Guitland freaking electric guit boxes, axes, rock & roll man. If Mick moves to the States, the default GFCI will rise exponentially :)

[@mtahirfilms]

Excellent video, John. I've got several extension cables that have mains filters on them. Can these contribute in causing the RCD to trip? Thanks.

[@jwflame]

mtahirfilms They can, as filters usually contain one or more capacitors between line-earth and neutral-earth. The current which can flow to earth is limited to a small value by the filter design, but if many of these filters are connected to a supply from a single RCD, the combined current can be enough to trip the RCD.

[@mtahirfilms]

Thanks John. We've had RCD trips for the last week or so. We're trying to find out what the problem(s) are. We've removed all the surge protected extension leads. We've pretty much removed everything from the wall sockets in the house. Is there a way to do some simple tests using a multimeter on the surge protected extension leads to see if they're ok?

[@samnewman5129]

How much would you estimate the cost to change an old Wylex for shower to RCD parts and Labour any idea ?

[@heronimousbrapson863]

It would like to see you do a presentation on how arc fault interrupters work. They're all the rage here in North America now; I don't know about the UK.

[@jwflame]

It's on the list to do. They are virtually unknown in the UK, although changes to regulations from 2019 recommends them for some situations.

[@sajad459]

Hello JW, do you have any idea why bs7671 forbids using RCDs in TNC systems? I know that it's not a perfect protection but at least would increase the safety of old buildings which don't have any earthing and bonding.

[@mariusa5754]

will electricity boxes in houses (in the UK) have RCDs in them or is it just circuit breakers.

[@jwflame]

+Marius Ammann Newer installations (under 10 years) will have RCDs as they are required on virtually all circuits. Previously (10-25 years) RCDs were required for socket outlets only, and before that they were typically not used at all.

[@MasudRana-mz3vt]

awesome explanation

[@alukic1]

if a neutral wire touches earth wire and then trips .is that good or bad ?

[@davidhaines4173]

Nice stick man J.W.

[@aydinnasirzadeh2190]

Can you please tell me if it is possible to connect an RCD the other way around? I mean for simple circuit breakers it doesn't make any difference. Is that the case for RCDs?

[@jwflame]

Usually yes - but check with the manufacturer to confirm.

[@bobhatcher5505]

John, "Im = 630 Amps" with the numbers on the face of the device. What current does that represent? (10 x device rating).

[@sbusweb]

+Bob Hatcher I think this is the 'making capacity' of the device -- if turned back on, that amount of instantaneous current may safely flow without damaging it. Notice this is far larger than the 'breaking capacity'. I think, due to this, good practice is to switch-off all subsidiary MCBs before resetting the RCD, then re-power circuits one-by-one.

[@VikashKumar-tk3de]

Hello john whether there are two CTs inside RCD connected deferentially means one CT connected at live conductor part(RCD) and other CT connected in neutral(RCD) and these both CTs connected to relay. When leakage take place current flow to the relay.?

[@zerosparky9510]

thanks for posting this.

[@adab4586]

It is helpful video, thank you very much but I want to ask you some question: 1- how the current amount will be the same on neutral line back of load as phase line, in another words how the consumption of power will be on voltage or current amount ??? 2- how the transformer will be in one end 0V and the other end of transformer not effected and stay 230v when you connet the 0v end to the ground, although the two ends in the same wire??? I will be glad if you answer me

[@computeraddic675]

A transformer isnt just a wire with two ends.Its a coil and because of that there is a magnetic field.A magnetic field has always a zero and a live side.Even in Direct Current(DC)I hope i enlightened you with my poor English.

[@annatsukiya]

Between RCD & ELCB which one is more reliable and safer to use? I heard RCD is the upgraded version of ELCB, is that true?

[@jwflame]

ELCB can mean RCD - RCDs are current operated and ELCBs can also be current operated. However ELCB is often used to mean older voltage operated types which will only trip if a fault occurs between line and the installation earth. They will not trip if someone touches a live wire or if the fault is between line and the actual ground.. Current operated types and RCDs will trip for faults between line and the actual ground so are far better, as they will disconnect if someone touches a live wire. Voltage operated types have not been used in the UK since the 1980s.

[@annatsukiya]

***** Oh I see, that's why RCD is preferable. Thanks. :)

[@ranjan1436]

Please make a video on the working of Isolating transformer used in Hospitals.

[@dabbab1]

I almost fell asleep twice in the first 2 1/2 seconds but things really picked up

[@macandconchita]

Thanks for the RCD information. I live in a remote area with no mains supply. I have a solar panel set up with a converter giving 5 Kw max at 230 V. I installed the system myself and put in rings protected with 2 pole "trip" switches. The main input from the inverter passes through a Hager "Residual current device - int diferential". I assumed that this would protect people who touched a live wire and the circuit in case of a short. Neither of my cables is connected to earth hence both sides of the system are "live". Your video tells me that i got it wrong. What should I do? or where can I find the required information? I will be grateful for any help you can give.

[@jwflame]

Mac Mudie The RCD won't work, as there is no reference to ground. However this also means people would not generally get a shock from touching a live wire, unless a fault to ground has already occurred within the installation. There are various methods of protecting such installations, further info here: xo4.uk/x/ect178.pdf (PDF document).

[@adus123]

Good video thank you I just got a 1500w inverter and was thinking of buying a plug in RCD for more safty. But now i see there is no point as it wont work thank you. saved me some money lol. Plus intresting video.

[@olkofri]

Thanks for the video, one question, it does matter how you wire the RCDs, the flow between blue and brown (life and zero) need to be opposite on the RCD. You cant just put the outside life and zero on the top contacts on the RCD, if I understand this correct.

[@jwflame]

Some RCDs can be wired either way, others not. Check the manufacturer's information.

[@fester.]

hello john i enjoy watching your video's and i have learnt a lot,i have a problem now as i bought a 3500watt inverter not a cheap one and i had a transfer 3 way switch installed 1 being the grid 2 is off and 3 being my inverter/generator anyhow as soon as i turn the inverter on my new split load consumer trips i have 2 63amp rcd 30ma.It trips when i turn the downstairs sockets on the inverter as inlet and outlet 230volt and the inlet is turned off by the breaker in my garage where the inverter is mounted i also have a earth rod ground and all my equipment is grounded DO YOU HAVE ANY IDEA WHY thanks john

[@bthnbgdt]

when there is no energy in the system, RCD yet recognise somehow and turns off the circuit. I experienced this when 3 phases and neutral connected to RCD and make ground and neutral short circuit from output of it. How that happens?

[@jwflame]

Voltage difference between N & E due to loads on other circuits, when N*E are shorted, a small current flows between them and that current is what trips the RCD.

[@meandmymouth]

As a total amateur DIY idiot I would not dream of connecting anything to the permanently live mains supply as required when say upgrading a supply panel but without revealing any dangerous trade secrets can you indicate what safety precautions a competent professional would take when doing this work. I understand that they may use specially insulated gloves etc. Is this true or just a myth ?

[@jwflame]

meandmymouth When replacing a fusebox or consumer unit, power would be disconnected by removing the cutout fuse, so no need to work on any live equipment. Protective face shield and gloves should be used when removing the fuse, in case of something breaking or failing when doing so. For work on the distribution network such as connecting a supply to a building, that is generally done live, and there is a whole range of insulated tools and protective equipment for use in those situations. That type of work would only be done by those employed by the supply company who have been specially trained to work on live cables.

[@meandmymouth]

***** Many thanks again for some more interesting and valuable advice. I have watched some American KZbin vids about this subject which don't seem to mention the safety precautions to be taken like the cut out fuse and protective clothing you explained. This seems rather dangerous and irresponsible ? Is the cut out fuse located in the supply panel ?

[@yogiontour]

brilliant channel bud

[@armchairmachinist2416]

Hi John, want to understand what happened.... I switch the CB off for one circuit of a wall socket , other in use, and replacing the socket as it was broken, I think by mistake the N touched with the Ground, nothing happened, just the RCB went off . Is that because the returning current from other circuits ( all N are connected together in the panel ? ) found a shorter way to earth and caused an imbalance? Again No live on that circuit. Thanks

[@jwflame]

Yes, the neutral is still connected and due to current flowing in other circuits the neutral will have a slightly different voltage to that of the earth. Connecting the two together causes a small current to flow via earth instead of neutral, and the RCD detects this imbalance and trips.

[@armchairmachinist2416]

Thank you for the reply.

[@miguelrosales3631]

excellent explanation, I have a question on another topic, I hope you can help me, I have a pool pump that works with 2 wires 220V, 110V per wire, (without neutral), would you recommend me to put a differential circuit breaker? If your answer is affirmative, how would it be, since the circuit breakers bring phase and neutral, I would need a 3-wire circuit breaker (2 phases and 1 neutral) where I connect the output neutral, if the pump only requires 2 phases (110V), , waiting for your attentions, thanks a lot

[@jwflame]

2 pole, 220V breaker, with just the 2 phases connected. Neutral not required.

[@miguelrosales3631]

MCB or RCBO or RCD TYPE ? THANKS

[@olegsk.9288]

Hi,JW ! Have You heard anything about electronic RCD? Which contains electronical components inside instead electro-mechanical...

[@andrewjames3908]

How does the test button on an RCD work when it doesnt have a connection to earth? I would have expected it to connect a resistor between line and earth

[@jwflame]

It connects a resistor between L on one side of the RCD and N on the other, causing some current to bypass the RCD. Some RCDs do use the L-E method, such as RCD plug adaptors or sockets with the RCD built in.

[@londontrada]

Why can the wires be smaller in the modern version? Surely they are still taking the full load?

[@jwflame]

londontrada The coil windings on the newer versions are only used to sense the tiny difference in current, the load current is on the pair of larger wires which pass through the centre of the sense coil.

[@dafyddmg]

Hi john, would an rcd still operate if there was a cross polarity?

[@B1cam]

Hi Jon . How does RCD testing using a tester work, a tester for example inputs 2x and 5x voltage. ie how does it create the imbalance to earth? Thanks for the videos.

[@okaro6595]

A tester simply has a resistor between the line and the protective earth. This creates the fault. This also means that a tester will not work if there is no protective earth. The test button on the other hand creates the connection between line and neutral bypassing the RCD so it does not need earth.

[@ws74rq111]

Hi John, Great video. I am installing an electric shower in an upstairs bathroom and the consumer unit is downstairs. I have purchased a stand alone RCD which I want to install directly above the consumer unit as the shower cable goes up to the bathroom. Being A.C. does it mater which way round the power goes into the RCD ?. Obviously for simplicity I would like the power to go into the bottom of the RCD out of the top. Many Thanks...

[@jwflame]

+ws74rq111 It doesn't usually matter. Most have a diagram on the side to show the wiring arrangement.

[@ws74rq111]

+John Ward . Thanks for the speedy reply so late at night. The only difference I can see is that the internal circuitry of the RCD is powered down when tripped as they would now be on the "cold" side of the internal switch. Goodnight and thanks again.. Regards. Paul,

[@أستغفرالله-ج7ت2ش]

my question to Mr Ward... does the earth connection can compensate for RCDs or vice versa??? what happens if both are existing in a appliance (e. g. geyser)? which one of them is the most important? thanks in advance....

[@jwflame]

The earth is most important. An RCD is for additional protection, not an excuse for a missing earth.

[@Cruner62]

Hi john, Another question. On a caravan site we connect to a pillar with our connecting leads if, for any reason, the earth in the cable or the supply pillar lost this connection to earth would the contact to earth by the caravan legs be sufficient to trip an RCD in the van under the same circumstances as my earlier post.?

[@jwflame]

+John W In most circumstances yes - however not guaranteed as it all depends on the condition of and type of surface the legs are in contact with.

[@Cruner62]

+John Ward Thanks John and understood.

[@peterdown9924]

Can you please give your opinion when testing RCDs? If I use the A or F setting on my MFD to test an AC type rcd and it passes the tests with appropriate readings, is this rcd therefore equivalent to an A or F type? Great vids BTW. PD.

[@jwflame]

No, only devices designed to be type A, F, B or any other are actually suitable for use in those applications. Some may trip with current waveforms they were not designed for in some circumstances, but that doesn't change what they are.

[@peterdown9924]

@@jwflame Ok John ,thanks for that. PD

[@danhackley]

Are you saying "live and neutral" when referring to the 2 channels of the device, or "line and neutral"? I can't quite hear.

[@jwflame]

It should be line and neutral. However the old descriptions of live and neutral are still very easy to use.

[@anandakrishnan9462]

Hi JW, Why my RCD is tripping frequently during a thunderstorm??

[@davem1658]

hi john. In my power box the active wire from my main switch- goes into the breaker- then the rcd- then into the house, rather than what seems standard; wire from main switch- rcd- breaker - then into house ..... is this ok? and I'm thinking if I put in another rcd for other breakers I will copy the existing rcd setup.. what do you think?

[@jwflame]

Doesn't matter, most consumer units are configured with the RCD first, but it will still work exactly the same the other way. Or use RCBOs which are the breaker and RCD combined into a single device.

[@davem1658]

@@jwflame thankyou- its hard to find this information on the internet.

[@allezvenga7617]

Thanks for your sharing 👍

[@ericbeckett4474]

hi john what is the difference between 30ma and 100ma rcd which is the most sensitive of the 2

[@pjeaton58]

The 30mA is the more sensitive.

[@vinayakpote538]

simply good... thank you.😀

[@has997]

what about if i use 3 phase machine supplied without earth from 3 phase RCD ( lets called RCD 2 ) and ( RCD 2 ) supplied with earth from ( RCD 1 ) , is that machine and user in safe ?

[@thomaslim6327]

very good video

[@makoesim]

Thanks a lot, can you explain how does 3 phase RCD work, especially it's keep working and recognizing electric leakage even with unbalance curents conditions between phases, it must be required a complex electronics elements to control that

[@jwflame]

For 3 phase, it's a single sense coil around all 3 phases and neutral, which will always sum to zero in normal operation.

[@makoesim]

@@jwflame John Ward even with unbalance load between phases? when the current that flowing in phases not equal then the magnetic field not equal and that's mean the magnetic field sum not equal zero

[@jwflame]

@@makoesim Yes, if the phases are not balanced, there will be a current in the neutral equal to the imbalance in the phases.

[@makoesim]

John Ward i got it, last question, i have un auxiliary power suply, can i connecting two rcds in seires nutral? or should connecting them in parallel and controlling the neutral by relays?

[@stephenjames8560]

Great video - thanks. I have a 3 phase supply coming into my house here in Bulgaria. I have a 3 phase RCD fitted an elmark JVL 1 and this is the first connection from the mains cable. It has been wired with the supply in at the bottom connections. Is this OK ? Thanks Steve

[@jwflame]

Yes, most RCDs can be connected either way.

[@stephenjames8560]

Many thanks John.

[@heronimousbrapson863]

That's interesting. Three phase supplies in North American houses is rare to non existant.

[@gd-bq7em]

Hi john if installing a spit load consumer unit on tt system with 30ma rcds do we need to install 100ma rcd or a 100ma s type rcd before it if so how do you test one and what are the trip times thanks

[@jwflame]

If all circuits are covered by 30mA RCDs, then a 100mA RCD is not required. 100mA time delayed types were typically used where some parts of the installation did not have 30mA RCDs, such as with split load type consumer units installed to the 16th edition. That allowed the 30mA to trip for a fault on those circuits without the 100mA tripping as well, and also provided protection for faults on circuits which did not have the 30mA RCD. For new installations, virtually everything should have 30mA RCDs / RCBOs, so 100mA time delay RCDs are seldom needed or used. Could still be of use in a few situations such as a submain from the meter to a distant consumer unit. Trip times for 100mA time delayed should be between 130ms and 500ms at the rated current (100mA). Trip times for various RCD types are in Appendix 3 of BS7671, page 363 in the blue 18th edition.

[@gd-bq7em]

@@jwflame ok j.w brilliant thanks for the advice. I will have a look at that

[@rezatarighat3524]

nice videos . many thanks

[@قَمْعُالفِكْرِالرافِضى]

I have 2 comments 1,I refuse to connect 0v with earth 2 only one turn in winding coils arround the ferrite Thanks