Types Of RCD

Types of Residual Current Devices, Type AC, A, F, B and B+. What each type is intended for and what fault currents they will work with.
Effective September 2022, BS7671 requires a minimum of Type A for the majority of installations.
However some devices are not suitable for use with Type A and require others such as Type F or B.

[@bigclivedotcom]

Bizarrely, many of the type A RCDs are actually technically simpler than the traditional type AC. Often with passive electronics and magnetic remanence latching of the trip mechanism. If they start making them too clever they may end up like the arc fault detectors where they contain so much active circuitry that they pose a huge reliability issue.

[@manickbarry]

So true

[@jimmjl]

What's Bizarre is that I can hear you as I read your comment! It doesn't happen when I read other posts.

[@nickbradley3966]

@@jimmjl Now you've said that, I can hear Clive too 8-)

[@theodorgiosan2570]

You should take apart an American arc fault breaker (AFCI). I've seen an arc drawn between hot and neutral and the breaker doing absolutely nothing. The manufacturers don't provide any good information on how they actually work, and some states here have even removed them from the code because they are insanely expensive and it isn't clear that they actually do anything.

[@maiyannah]

It almost like the electrical standards are more of a certification racket than meant to actually provide timely guidance to the professional field.

[@g7mks383]

Yes agree it's been a closed shop money making racket for years.

[@multiskilledelectrician1]

Yes, exactly my thoughts.

[@theodorgiosan2570]

You should see the American code. AFCIs (AFDDs) required on almost all circuits. Not clear that they do anything because I have seen arcing with the breaker not tripping. Some states have removed them from their codes. Another ridiculous one was the code requiring GFCI (RCD) on permanently installed outdoor air conditioning condenser units. When most of them don't even work on a GFCI breaker and will instantly cause it to trip. Not to mention that breakers big enough don't even exist in a lot of cases and when they do, they are $200+. This was done because someone was shocked by a disconnected wire that touched the metal casing of the AC condenser, one that was installed with no grounding conductor. Strangely enough they did not require a grounding conductor, which would have solved the problem, but instead they required a ridiculous 60+ amp 2 pole GFCI.

[@e5Group]

Back once again. Never gone in our hearts.

[@craigchamberlain]

What a treat to see a new video from you JW, very informative as always. I hope you are well and I hope to see more great content from you in the near future. As some others have requested, a video on how to safely connect small domestic generators to our installation in the event of power cuts this winter would be fantastic. Especially for installations which might already have a mix of solar PV and battery storage but might need to supplement this with a generator to keep the lights on and central heating pump spinning on the darker winter days.

[@bigclivedotcom]

I've noticed an ongoing issue on eBay where the original type AC RCDs are being removed from consumer units for replacement with type-A units and then sold off on eBay by the slideshow-electricians who don't seem to understand why they had to swap them in the first place.

[@croikeyaustralianbetamales3432]

i dont see anything wrong with using an ac rcd for a consumer unit in a garden shed for example, or a 1 bedroom flat with very little appliances and nothing fancy in the way of lighting, different horses for different courses?

[@BPo75]

@@croikeyaustralianbetamales3432 With so many things using transformers in one shape or another, one can not rely on the AC keeping the sinus shape needed for such an RCD to work reliably, as while YOUR load might be perfectly fine, your neighbour might have a leakage out on the mains feeding your place.

[@theodorgiosan2570]

I'm in America so I don't have to follow the British regulations, but I do use DIN rail RCDs and RCBOs in control panels I build. Type AC is perfectly fine for something like a hardwired compressor with a mechanical pressure switch controlling the motor. Or any other large motor powered tools with no electronics, resistive heating elements with mechanical temperature switches, etc. I choose the type of RCD based on the load it serves. If it's receptacles or light sockets that anything can be plugged into, I will use a type A or B. Hardwired motor or heater with mechanical controls? Type AC. Motor with VFD? Type F. Welder or something else with a rectifier? Type B. But then again almost everything that is wired up to one of my panels is hardwired and large enough that it wouldn't be very likely for it to be replaced rather than repaired. In a typical situation you wouldn't want to do it that way usually. So for my situation I often find myself buying the type AC RCDs from the UK. So it's possible that they are being shipped internationally, they are extremely inexpensive compared to what we have available here, all of which are the equivalent of type AC.

[@JohnSmith-ys4nl]

@@theodorgiosan2570 I am in the U.S. as well. What "type" are our typical household receptacle GFCIs? Our "type A" seems to mean something different from Europe's "type A." Type A over here simply means it trips at 6mA - it says nothing about the waveform.

[@edc1569]

Using “type” for the overload current curve and the rcd technology, with the same letters is a stroke of genius for the IET.

[@johnburns4017]

They also get paid a lot of money to create such confusion.

[@markbradley5746]

Stop thinking logically.. Dont you know by now society deliberately creates difficulty and confusion in our modern day ... thats how corperates make money hand over fist.. We no longer use technology to make life easy like we use to.... Once mankind found computer technology could be eased to control us while under the guise of giving us a better life... the shareholder got a boner and became in charge.😮

[@iamdarkyoshi]

Well explained, and interesting to see it took so long to set the standard to something modern. Glad to see you back!

[@Roll_the_Bones]

The legend returns! JW talked me through the whole process of re-wiring my whole boiler Y-plan control cabling, when the company who installed my new boiler ran away from upgrading the original knackered Honeywell combined controller to a new fully-programmable Drayton unit with the newer standard backplate. "You need a specialist electrician mate!" the spannerman said. So I did. Cheers JW! 🙏 ps. your YT icon looks like Brains from Thunderbirds, very appropriate.

[@jaessak3463]

Great video John. Knowledgeable and keeping us up to date with current standards of BS7671. Thank you John.

[@Kx7nnnnnnnnnB66]

Intresting video .glad to see you are back .thank you . All your videos are great to rewatch

[@neilcowmeadow3551]

Thanks for another excellent, clear and well explained video, John.

[@clivequinn8978]

Well explained. Great to see JW back.

[@leehewitt9559]

Great video John. Very informative as always 👌

[@JIBS.]

Love your vids John. Would love a good video explaining how to fit AFDD's when you come across main switch RCD boards and split load RCD boards and ways round it to fit in to the regs.

[@tommyhanlon8012]

Even I understood that. Great to see you J.W.

[@hopebgood]

It never ceases to amaze me how there's a vid for everyone on YT! And I mean that in a nice way.

[@g0fvt]

I am glad you covered this, it had bothered me that the AC type had that limitation,. I don't know whether the others are possibly faster, the AC type only sensing on one half cycle.

[@simmo1024]

The Horowitz and Hill Art of Electronics book on the shelf there is the same one I have - it is an excellent book. Now I am going to spend the rest of the video looking through the bookshelf instead of listening to RCD talk!

[@artisanelectrics]

Great video John thanks a lot

[@electrician247]

Very well explained John, thanks!

[@IcenI_Koi]

Been a while JW, very informative. Thank you.

[@raithwilson6845]

Hi john Love your work on here .I am a niceic approved contractor.Have been for many years .Last week iI was testing in Rotherham .A small terraced house/The cu had 4 mem rcbos type ac.All of them would not trip in situ.Apparantly being stunned by the dc component .We later tested 4 more houses on the same street .No ac rcds would work in them either.I brough in a scope and checked the waveform at the supply and found dc on the supply to be around 15ma.Hers the thing that I think everyone has overlooked.Whats to stop and rcd being stunned from incoming dc ? Answer? Nothing!So it seems in theory next door could have alot of dc content in their home or indeed even an industrial unit a good way away could be capable of stunning an entire estate with ac rcd type in the installation.This is could be a problem overlooked on a scale never seen before in the electrical industry.I will be writing to the niceic and IET to see how they decide to shit themselves about there new 18th am 2 and how there will most likely be urgent action of a mandatory filter to be fitted at the supply of every installation in the the uk ..The dc component will just go through the rcd and stun it from either supply or output.Nothing to stop it .The other frightening thing is that it was 15ma which would propbably make an a type useless too.I will find this out when I swap them out next week.Whats your thought on this?

[@joesmith-je3tq]

First I have heard of type F. I have known many people who have had new construction that required RCD in their kitchens. Their new appliances (fridge) which use new motor type will then shut down. I've also known people who have similar problems with their pool pumps. The electricians don't have a good fix. This has been needed for 10 years. Maybe you will consider getting your hands on a few different ones to test. Thanks for taking the time to put this video together.

[@akdenyer]

Hi John, glad to have you back. Interesting collection of books. Horowits and Hill I used at university. Interesting how you can tell the person from the book collection.

[@sergiofernandez3725]

Great explanation JW. I always enjoy your videos

[@tijjaniabubakar3698]

Hi John You are doing great work to electrical installation work More grease to your elbows🎉

[@lawrencer25]

Welcome back. Fabulous video 🤓🤓🤓👍🥂🥳

[@johnavery15]

I wondered when we would see another JW video. Love the background!

[@markhorton8578]

Yes the great silver grey "Art of Electronics" visible, as it is with so many electrical and electronic experts worth listening to. Some of the older books look interesting too but I cannot make out what they are. Looks like an interesting collection.

[@malachygallagher4936]

Hi John Following your videos for years & they are excellent! Can you do a video on generators? Eg. Bonded or floating neutrals? Regards mg.

[@alexwade9921]

Good shout! There’s very little advice about this. I’ve just been cobbling something quick together to get some power from a little (700W continuous) inverter generator into the house in case we get power cuts this winter. What I ended up with was a 16A Mennekes inlet (effectively a wall mounted ‘plug’) on my outside wall coming through into a three gang 13A fused MK socket, monitored on the way by a Peacefair PZEM-022 power monitor in a little IP66 enclosure (so I can see what I’m drawing from the generator, incl. power factor etc.). I worked out that I needed to cross-bond the earth of this setup to the indoor earth in case of mains or neutral to earth faults in equipment indoors causing dangerous potentials between them, or in case that a PME or open PEN fault on the main did the same, also creating dangerous potentials indoors. The one thing I can’t really account for is that if I return the mains earth all the way to the small generator, then I can’t protect against a PME fault causing a shock risk at that point. Within my generator itself, neutral doesn’t seem to have continuity with the generator earth. Should I just let the generator float connecting it with two core flex? Who knows? In the interim, I’ve placarded the indoor socket with advice to connect the trailing lead from the generator to the house inlet last, then disconnect that end first before approaching the generator minimising the risk of a PME fault shock to local earth.

[@ranat5526]

Good to see you again!

[@Duddi1966]

Thanks, Interesting. Type AC has not been permitted for residential applications here in Denmark for decades

[@dollarama8652]

Thanks for the video... be well.

[@bjornroesbeke]

With the advent of electric cars, my local laws have changed to require type B RCD's upstream of all EV circuits. I've never encountered a type AC RCD and checking §5.3.5.3 of the regulations confirms that type A is the least protective type that's still allowed. They don't explicitly say whether type F is allowed, nor do they state a definitive trip delay.

[@christastic100]

Very clearly explained Mr Ward . Can you explain what the technical reasons for not putting any other type of RCD up front of an old type ac .

[@edgar9651]

Thanks!

[@FinlaysFireSystemsElectrical]

I like how John is slowly becoming to look like Einstein

[@solidus784]

Funny, I was only looking this up last night then a J.W video nice👌

[@alanmarriott9216]

Great video John. Any chance you could show in depth about Rcd blinding when wrong Rcd is installed or currently installed when doing ev charger for example please?

[@charliea697]

Some of the best content on yt.

[@g7mks383]

Very good and well explained video thanks. But O dear if ever an organisation existed to generate money. Have you seen the cost of the new regs books.

[@solpcb]

Lovely explanation 👌🏼.. I see you have some very old and interesting literature on the book shelf, esp 'The art of Electronics' by Horowitz an old favourite of mine 👍🏻. Your haircut reminds me of man I went to visit in my time machine, Very cool 😎

[@tonythorrington3740]

Welcome back finally some new content

[@ninaevans4501]

Indeed, Mr Ward. Common Sense and Responsibility, clearly, are no longer on the curriculum of modern education. Wayne & Nina

[@cdturri]

Great video, I recently upgraded my consumer unit as I was running mains power to my shed and I didn't have any space left for more circuits. I went with all Hager Type A RCBOs but if I would have seen this video I would have gone for Type B. These do cost a bit more but if you are going for individual RCBOs best to go for something more modern too. I bought them online at edwardes. They have loads of Type B RCBOs for other brands too and were great to provide a replacement when one of the RCBOs wasn't properly painted. PS: Of course all this work was done by a qualified electrician and signed off/certified as part P.

[@philipdarton1002]

I have never seen a type B RCBO are you sure there are loads? The B normally refers to the mcb part not the rcd part so when it says B6 or B32 it is the mcb that is type B not the rcd

[@Marcel_Germann]

There's no RCBO available with a type B RCD functionality. They're usually type A, and that's sufficient for the use in a regular domestic dwelling circuit. Here in Germany the type AC RCDs were already banned in 1987. Standard type of RCD protection is the type A since then. Don't confuse it with the B tripping curve of the MCB part of the RCBO. The selection of the proper RCD must be made according to the possible dangers that can occur on that circuit and that is depending on the appliances that are connected to it. The chance of having a dangerous smooth DC voltage on a regular socket outlet circuit is almost zero. Where it makes sense is when you install an EV charger without DC protection. The ones with DC protection just want a type A RCD, the protection against a DC fault is included into the charger itself. That is actually sufficient. The smooth DC most household appliances have is in a safe range. On EVs it's a completely different thing. For example the battery of a Renault Zoe has 400V DC and can supply a lot of power, so that is dangerous and requires this additional DC protection.

[@cdturri]

​@@philipdarton1002 Go to edwardes and search for Type B RCBO. There are loads. I can't post the link as it gets blocked by YT.

[@markrainford1219]

@@cdturri I looked. All Edwardes RCBOs are type A. Many are labelled Type B, but that relates to the operating curve of the MCB side. Pricing is mostly effected by whether they are single or double pole switching. The cheaper ones tend to be solid neutrals.

[@mernokallat645]

@@Marcel_Germann What type of fuses were used in Germany before the D II bottle fuses being commercially widespread in the 1910s?

[@Xclub40X]

Welcome back... Long time no see

[@asdreww]

Welcome back. My new CU from around 12 months ago is full of BG type AC RCBO's... annoying

[@swirlingmurk5342]

There are many very old Type A BS4293 RCCBs in the wild and also many Eaton RCBO pods for the MEMshield 2 MCBs which 99% seem to be Type A

[@MalinDixon]

Some hair dryers still use a diode to produce the half power setting.

[@alunroberts1439]

I do remember pages coming up were techs were saying the grid needs to be changed to DC. And at 48v and using DC with inverters in each home. I have stuck my tester in to a socket and the killed the power and measured the DC coming back out on my desktop PSU and other electronics. So with all the appliances there must be a lot of DC on the line.

[@loc4725]

That was interesting, thanks! I just had a look at ours; the sparky whi did the work failed to give either us or buildings control a certificate and the NCIC had to be...'politey asked' to give us one, so I've been a bit suspicious as to whether the job was done properly. Looking at them there are no symbols (only compliance marks) but apparently we have CIT branded type 'B', so at least that's good. 🙂

[@leemckerrow1986]

The b6 or b32 etc is not a type b mcb. It will be type ac or a

[@thewaveringwarrior]

Hi John, you videos are always very well explained. I presume when you describe a type F rcd working at up to 1khz, I guess you mean if a switch mode psu working at say 1khz decides to leak to earth from a fault in its internal oscillator then it will trip at its In value?

[@ninaevans4501]

Very interesting (and informative) video from you once again Mr Ward. It is indeed, amazing how electrical H&S has evolved over time. Myself, and other half, were both born in 1971. Back then, British Relay Colour T.V. sets were full of valves that glowed bright orange, and became extremely hot. The sets were housed in wooden cabinets, with a kind of cardboard "rear end". Plumes of acrid magic smoke often arose from these units at least once a week at best. "Redifusion" service engineers almost lived here, they had to come round and repair these disgusting pieces of equipment so often. In short, if something wasn't right electrcally, you left it to the professionals. You didn't cut wet grass with a mains powered mower, and were always careful not to cut through your flex when trimming your hedge. Electrical H&S IS a good thing, BUT IT CAN ALSO MAKE US TAKE THE DANGERS OF ELECTRICITY FOR GRANTED AT THE SAME TIME.

[@jam99]

You're talking about education, aren't you? It was previously known as 'common sense', but people took more personal responsibility in those days. Fewer parasitic lawyers were ready to launch themselves at you to support your idiot (or malicious) actions in order to try to screw money out of a company.

[@chriholt]

Thanks for the detailed explanation. I was fascinated, even though I'm in the US. By the way, whatever became of the phase converter project from a couple of years ago?

[@jwflame]

Phase converter is mostly assembled. It will be in a video at some point.

[@daveaustin53]

Be useful to have some further info on testing requirements for the A, F, B types as a standard mft probably only generates AC leakage current to test?

[@nickbradley3966]

Thanks John , that was excellent. Would an old AC RCD be insensitive to the other types of fault current (e.g. DC pulses, high frequency current etc.) and not trip when it should, or might it display nuisance tripping in the presence of safe levels of them? I have an old split consumer unit. I assume that the RCD is type AC. I've just had a solar and battery installation and now I have regular RCD trips. I can run nearly all my circuits, but the last one I close trips the RCD. The one that causes the trip isn't consistent. Sometimes it stays in for a few minutes. It seems to be that each circuit has a small earth current and with them all in, it trips the RCD. I replaced the RCD with a new one identical one and it became worse. And advice would be greatly appreciated, thank you.

[@ianmiller3182]

I think maybe the equipment manufacturer needs to provide information on the type of RCD protection needed as I believe some do. Else we we could end up with the scenario of inadequate protection being fitted and the possible defence could be that there was no particular recommendation from the manufacturer who could have the last say on the installation.

[@MyMyian]

When you plug a phone charger or the like into a socket does that constitute DC with all the associated circuitry, diodes etc?

[@alexwade9921]

Great video. Pretty timely for me because I’m just looking at EV charging. After some head scratching I’d just about already worked out that I need a type A and a downstream charger that detects greater than 6mA DC leakage, or a type B. Most important of all, also a PME fault detector though! I don’t think I can get a bullet proof TT earth. Why on earth is pretty much every supplier still selling type AC? It’s ridiculous. If you go to Screwfix or similar and by a consumer unit with modules off the shelf it’s all type AC!

[@jam99]

Look at chargers with everything built in. They cost a bit more though. Something like a Zappi does not need earth rod, nor external expensive RCD, as the safety is built in. I expect others are available cheaper with the safety but without the fancy functionality built in.

[@smarty0604]

Nice video mate very clear and easy to follow 👍

[@davoc5140]

Great work as usual John

[@ZerHour]

Brilliant video , for say motorhomes with inverters and solar panels on board which RCD would you recommend the Standards say Type A , but would type B be better ?

[@andrewturpin1994]

What are your thoughts with a touring caravan that has a charger/converter to charge a 12 volt battery that runs most of the equipment in the caravan and many have solar panels that also charge the battery

[@iDoWayTooMuchAcid]

Wow, been a while since I sat down and watched some JW! Usually (and currently) I watch JW while enjoying a doobie while on front porch… god I love getting educated.

[@anthonycurran362]

Thanks sir,great advice as usual. So I assume the AB unit will cover all eventualities?

[@ayrtonspark3661]

I live in a house that has type ACs..we have an induction hob, all LED lights and two inverter type Air cons and we don't have a problem with RCD trips... I have tested them with a MFT and they work fine. The Z's checks out too.. maybe because it's a TT system?🤔

[@blueyhis.zarsoff1147]

Great video John I assume as each version of the rcd can deal with the more complex signals on the wire a modern signal cant trip an older rcd? Q. So no nuisance tripping with the wrong version to suit your requirement?

[@MrKarlPrince]

Hi John, Excellent content as always, are you aware of any resource that shows which manufacturers supply "RCD type" F or B RCD's/RCBO's devices for their consumer units? Would be nice to install a board that have the required options available for near future expansion.

[@jwflame]

No. Most domestic consumer units have only recently moved away from Type AC, anything else is total fiction for the majority at this point. Even obtaining F and B RCDs for commercial distribution boards is far from straightforward, they do exist but choices are extremely limited.

[@mathman0101]

@@jwflame and very expensive with an EV install really type B or B+ should be really the standard. Time delayed - I see Eaton offer type G and type S. Programmable frequency RCDs/GFCIs are theoretically constructable but once you get into much higher frequencies beyond 2khz and or aperiodic frequencies it can get very complicated to fine tune the software encoded on these devices. And yes it’s pretty much software rather than hardware on its own - to recognize and filter the various frequency types. The other route some manufacturers here in the USA go through is to modify the output signal and apply chokes and filters to remove multi-frequency and higher frequency noise say from VFDs allowing a cleaner signal for the standard type A GFCI protection to work that is quite the rage here in the USA with VFDs on air conditioning units. After this a discussion of selective coordination is really needed not just for GFCI or AFCI protection but also for overcurrent protection including mixed use of breakers and fuses….

[@BPo75]

@@jwflame In Sweden it's not a problem finding them, though were type A typically is in the span of 250-700 SEK, type B is considerably more expensive, with the a span between 3000 - 6500 SEK, not counting the no-names and uncertain Chinese brands like Chiant and Rogy.. Type F is rarer, but readily available in the range of 700-1200 SEK. It seems like the shift is under way at least.

[@SonofChurchill]

JW not see for sometime. hope well. Vid alway interesting

[@MagnetechSolidSolutions]

John, immersion heaters are not going away. They are increasing, additionally immersion heater boilers are the next new craze with gas and oil boiler retrofit

[@An.Individual]

My 240V mains fuse panel has MK 5706S, I just checked and they are type AC. Should we be getting the Type AC RCDs replaced urgently? I'm thinking so what if they don't work with DC, UK mains is 230V AC and always will be.

[@johnburns4017]

John, you might want to do a vid on AFDDs, as they are now mandatory in blocks of flats in 6 floors and over on circuits with sockets. They are also _recommended_ on all installations. As AFDDs are so expensive, I see going back to one large ring in a flat/small house (maybe a 4mm cable ring). It would be interesting to design the cheapest electrical system incorporating just one AFDD, conforming to the regs of course.

[@alexwade9921]

An AFDD doesn’t work properly on a ring. It won’t detect a series arc because current can flow around the other side of the ring and ‘blind’ the AFDD. I think everything will go to radials and, in time, every circuit will have a single pole MCB/RCD/AFDD combined of the correct amperage.

[@johnburns4017]

@@alexwade9921 A ring reduces the arc as it is fed from both ends. So an in-built safety aspect of a ring. It will detect a large arc on a spur off the ring. The ring is here to stay in the UK. it is too good. Right now AFDDs are expensive, suggesting multiple radials with AFDDs is not economically going to work for many when other cheaper solutions are here. If fitting out a new electrical system with sockets circuits then reducing the sockets to one circuit, with heavy appliances on radials on RCBOs, will reduce costs. You can have a number of radials off one AFDD. Each radial can have its own fuse. The fuse carrier can be on a DIN rail in the CU, all labelled up. So one AFDD with a number of socket circuits off it. One could even be a ring. Cheap to do and well within regs.

[@alexwade9921]

Is it really a safety aspect though? If there’s a break in the ring due to a loose connection you then also have an inappropriately sized fuse/mcb/whatever and you won’t know it. I bet there are thousands of ring circuits that have been broken into radials by incompetent modification. A radial is so much more difficult to mess up. The only real benefit of a ring is that you get more current carrying ability for little more expense in cable or vise/versa. Modern appliances of every kind are more efficient than they ever were. Unless you’re using a fair few plug in heaters around the house then the 32A rings in most houses could quite happily be 20A or even 16A radials.

[@johnburns4017]

@@alexwade9921 If a ring is in 4mm cable with a 32A MCB/RCBO, then no problems if it is broken - which is a very rare thing. Many clearly do not understand what a final ring is to do. The ultimate is to have a radial to _each socket outlet_ on its own fuse at the main panel - the optimum solution of course. This means you will need a _very large_ expensive main panel and lots of fuses (one for each socket) in the main panel. 🎊🎈 *BINGO* 🎊🎈 *A ring gives this by distributing the main panel around the house via a ring cable,* distributing the fuses from the main panel around the building to each socket. *The ring is a busbar.* This saves the vast expense of a plethora of radial cables back to the main panel and also a plethora of expensive fuses/MCB's/RCBO/AFDDs at a _very large_ expensive main panel and expensive labour to install. *a)* A ring uses less cable and gives a longer route *b)* No limit to sockets on the ring, but total is limited to typically 32A. *c)* A ring uses less copper for a given load/area. *d)* Rings rarely have voltage drop as it is fed from both ends. *e)* Rings have lower impedance, less volt drop is less waste! They are more efficient. *f)* No single point of failure for the protective earth. *g)* If you are covering all rooms in one floor then a ring can do it. *1.* Ring final 2.5mm cable, 32A B-curve MCB, length *106m* on TN-C-S. *2.* Ring final 4mm cable, 32A B-curve MCB, length *171m.* *3.* Radial final 2.5mm cable, 25A B-curve MCB, length *33m.* *4.* Radial final circuit, 4mm cable, 32A B-curve MCB, length *43m.* Simple and highly effective.

[@alexwade9921]

@@johnburns4017 - A 4mm ring would end up being really expensive though! The cable is stiffer and harder to route as well. I bet there aren’t many around. That’s the real reason for a ring circuit. Economy at initial installation. Cooking and heating/aircon loads apart (and they are mostly dealt with separately) I reckon most houses are never using much more than 5A on everything else put together nowadays. 4mm everywhere is such a lot of copper!

[@michaelchapman4269]

Legend John, great video as always. Are we talking about appliances ‘leaking’ these frequencies onto your ac mains installation. Equipment providing screening and suppression to stop this happening? I’ve just come back from working in France and surprised they still use and supply type AC, for use in ovens, sockets, lights which back in the day like you say wouldn’t normally have any DC on the circuits, but that was like 30+ years ago now!! 😅

[@jwflame]

Partially - for the higher frequencies from things like inverter drives, some of that will end up on the supply. For others it's the current waveform that the device uses from the supply, many items with switching power supplies take current in pulses, and not always equally on the positive and negative cycles of the AC waveform.

[@l3w1s91]

The frustration I find is customers that have recently installed consumer units with type AC RCDs, I come in to quote some work and tell them they need to be changed. They almost don’t believe you as it’s been newly installed. 🤦‍♂️ the problem is type AC are still widely available at cheap prices like screwsfix etc .

[@l3w1s91]

Very informative and great videos as always. Thanks for your time and effort.

[@edc1569]

@@l3w1s91 why do they need to be changed on existing installs?

[@johnburns4017]

@Michael Chapman Yes in the three DIN rail row of _Legrand Lodgement T4_ main panels (which we stupidly call a consumer unit these days), they have an RCD for each row of DP MCBs. In Germany, France and Switz, all disconnectors at the main panels have to be DP, unlike the cheapo backward British, then they can have L and N bus bars making matters much easier - and do. At Leroy Merlin you will see for sale _Legrand Lodgement T4_ three row main panels - search on them - with an RDC on each row. Max eight MCBs off an RCD. They have on each row: *1.* 63A RCD type *AC.* *2.* 40A RCD type *AC.* *3.* 40A RCD type *A.* The type *A* has the washing machine and hob off it. The type AC according to John is obsolete in the UK. The type AC and type A both have the A/C and pulsed DC symbol on them. French consumer units. Leave us standing. They also use cable in flexible conduit and no cheapo twin & earth cable. Easy to thread in and out of the conduit. Their regs have been updated greatly in the past 20 years. The French units can be bought unpopulated, just with din rails and din rail connectors with cable. Then use British RCBOs and busbars. They are plastic but they do sell metal outer enclosures. The British come in the bottom on MCB's, etc, while the French is from the top with two bus bars, one L and one N. Nicer. Note the vertical busbar on the left hand side of the T4 linking the DIN rail rows. Search KZbin on: _Can UK Electricians Learn from French Electrics?_ Also search KZbin on: _Tableaux électriques Legrand Drivia prêt à poser : comment installer nos tableaux précâblés ?_ This shows a legrand main panel being installed.

[@Longtimerolling]

Good info. I'm guessing Aus/NZ will have these new rules as well?

[@jwflame]

They have gone further, Type AC RCDs not permitted to be sold or installed in Australia from April 2023. Some parts of Australia banned them years ago.

[@mrxmry3264]

depends on their governments.

[@sonnyfung5135]

Really wanna buy those books behind you.

[@POLITICAL-BIAS.]

This is bloody complexed. You're a genius

[@tomsurrey2252]

Very good BUT, what about 'D' rated RCDs? I know they are mainly used for heavy industry / welders etc BUT... it would be great to hear what you have to say about them!!

[@jwflame]

Those are MCBs, covered here: kzbin.info/www/bejne/pJq9YWR6p8Rreac MCBs work on overloads and short circuits RCDs detect leakage to Earth.

[@blueyhis.zarsoff1147]

Q.Dual pole breakers, is there any time you could would should use one on a single circuit?

[@Clip7heApex]

If you're looking for a type B rcd or rcbo you are likely to come up with thousands of results for type B curve making it a pretty poorly thought out naming system.

[@markrainford1219]

Is pulsed DC as dangerous as AC, as in make you hold on or throw you off like smooth DC?

[@bigjd2k]

You try and buy one though! My solar install was done by a company with type AC breakers. Want to change them but they’re either out of stock or stupid prices.

[@TheGodpharma]

Not an electrician here, just an interested householder. I found this video after having a PV system and a Zappi EV charger installed (by different companies). The PV system has its own fuse box with a Type B RCD in it, and I understand the Zappi also has one built-in. The PV installers did not change anything in the main CU (which had Type AC RCDs) but the people who subsequently installed the Zappi a month or so later swapped out the Type ACs for Type A. Why was the change needed for the EV point but not the PV system, or was one of the installers wrong? Any why Type A not Type B in the CU?

[@G8YTZ]

Where I live there is a pedestrian bridge over the railway line, mopeds of these companies drive over the pedestrian bridge.

[@davidsteele3037]

I never understood the RCD types meant until now. I need a type B RCBO for a variable speed water pump but the manufacturer of my consumer unit doesn't make one. This means a separate RCD and MCB using up 4 slots.

[@johnburns4017]

Many RCBO are interchangeable from manufacturer to manufacturer. Find out which. They say do not mix, well they would say that wouldn't they.

[@lemech]

Hi, I have a split board with two 30mA type AC in the consumer unit and one 100mA type AC RCD outside of my premises. I'm planning to replace the two 30mA type AC with two 30mA type A. Since the 30mA type As are upstream of of the 100mA type AC RCD, would that be OK? I am not allowed to replace the 100mA RCD as it it outside of my premises. Thanks.

[@icarossavvides2641]

B+ 20KHz limit seems odd as induction hobs typically work around 32KHz?

[@gabrielhomeku185]

👍👍👍👍

[@khalidrash5814]

Hello sir, Should the outdoor service switch be greater or smaller than the main breaker in the consumer unit? I'll be so grateful if you would send me back. Thank you, Khalid

[@okaro6595]

In Finland type AC was banned 2007 at the same time when universal RCD protection was mandated.

[@arsenic222]

Hi John, is type A RCD sufficient for EV charger earth fault protection?

[@jwflame]

Yes if the EVSE has a Type B or equivalent in it. Most do. If not then a Type B RCD is required.

[@BipolarShango]

Where have you been John!

[@normanpouch]

Can we install a Type B RCBO for solar in the main board, or will the rcd trip anyway? Cheers.

[@jwflame]

You could if you can find one - most consumer unit manufacturers do not make them.

[@normanpouch]

@@jwflame Thank you John, top man.

[@Xclub40X]

When it comes to electricity.. I'll stick to JW... the correct type 🤣

[@MrSJT]

I'm pretty sure 30mA type B goes up to 12mA DC .. I think it was 40% of leakage current or 10mA whichever is greater, 40% of 30mA = 12mA.

[@kriskay2771]

John... do a video on air source heat pump wiring.

[@jamesclarke5331]

The regs have been requiring A type RCD in medical locations since 17th ed.

[@alunroberts1439]

Makes me think what if DC did win the battle. What would it all be like. With today's tech as I have powered up TVs computers laptop PSUs with DC as most the mains comes in through filter caps. Then to a bridge rectifier DC that we can feed with DC. What did confuse me many many years. We have ups systems taking 12v 24v 36v 48v to 230 to feed computers only to come back down to 3.3v 5v and 12v so would DC work today would it be better ???

[@brianhewitt8618]

👍

[@ambiencelectronica]

Hi JW. Would type AC be ok to install for dual supply isolators dimplex Quantum HHR storage heaters? Thanks

[@jwflame]

No, because those heaters contain electronics which is not suitable for Type AC.

[@ambiencelectronica]

Appreciate your confirmation, I’ll be getting them swapped out. Thanks

[@thewaveringwarrior]

Surely the Rcd is protecting the cable to the appliance or load. Ie a washing machine if it developes a fault on its DC side to earth then the fuse should trip. Are we talking about type F rcd being used to death by electric shock?

[@Chris_In_Texas]

So being in the USA, is there a big cost difference between say a Type A and Type B?

[@jwflame]

A are a similar price to what AC used to be. F, B and others are significantly more, anything up to 10x more as at the moment they are used in very few situations.