Can you still use TYPE AC residual current devices? (RCD)

Residual Current Devices (RCDs) are used extensively in modern electrical installations. However, the older type AC RCDs are now almost obsolete within the latest version of the UK wiring regulations BS7671. In this electrician's Q&A, Joe Robinson explains how RCDs work and why the Type AC is on the way out.
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🕐 TIME STAMPS 🕕
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00:00 RCD changes under BS7671
00:33 Types of RCDs
00:52 How does an RCD work?
01:30 Line and neutral currents
01:51 Earth fault
02:27 Loads with DC elements
02:40 AC sine wave
03:26 Magnetised core
04:45 Can I still use an AC RCD?
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[@efixx]

FREE training module - BS7671 Circuit Protection. www.efixx.co.uk/Know%20How/amendment-2-circuit-protection-cpd

[@mikeselectricstuff]

I tried to by a MK type A RCBO at a local wholesaler last week but they only had AC (After initially telling me they only had type B, which was actually the MCB characteristic) - the guy said they didn't stock type A's as nobody had asked for them before. Makes me wonder about the avarage sparkie's kmnowledge of the latest regs...

[@markpotter8280]

I doubt the wholesaler knew what he was talking about to be honest every new RCD or RCBO I have fitted for quite a while now has been type A off the shelf and every time I do an EICR I note down if the RCBO is type aC 5-4.13 I know this now off the top of my head I do it that often 🥲🤣

[@mikeselectricstuff]

@@markpotter8280 I saw the box - it was AC

[@markpotter8280]

@@mikeselectricstuff weird that they would only stock type aC even weirder that they said there isn't a demand for type A. but if that's all they had I guess you got what you wanted elsewhere.

[@conorgray6883]

I think some wholesalers might try and pull the wool over people's eyes and try to.get rid of some discontinued products, unfortunately.

[@elementaldraco]

I encounter it regularly with RCBO's where people get very confused over the system used to denote the RCD and MCB characteristics and mix up the meanings. Sounds like your wholesaler has a sales staff product training issue. There is one wholesaler I ues that has a terible habit of trying to make product substitutions with items of compleatly the wrong specifications when they don't have the specific item I have ordered in stock.

[@alanmarriott9216]

Great video. Could you explain earth leakage abut more please? How’s does a device leak dc current and why does it do it please?

[@edc1569]

In Europe the consumer unit is built into the home, if you wish to improve protection you swap in the necessary devices, you don't pull it out and bin it every-time some standard changes, you don't have a dozen additional opportunities for a mis-torqued connection burning your home down. In the UK, we can't use that 18th edition board anymore that you had fitted last year, time to chuck it in the bin while I bodge in this BG board. I'm starting to think the IET gets kickbacks, doesn't seem that hard to standardise a bus bar and a DIN rail, never mind suddenly realise 15 years later that Type AC RCDs are bit crap.

[@Marcel_Germann]

But only if the board still meets today's requirements. Otherwise that one has to go here too. Important is also that you install bigger boards with more space in it so you can retrofit devices in the future if necessary. The DIN rail is normalised, that is why it's called DIN rail, the dimensions are normalised by the German DIN, the German institute for standardization. BTW we call them literally translated "hat rail" in Germany, because in profile it is shaped like a hat. In Germany we purchase not fully equipped boards, we purchase all things separately. That means you can have Hager housings but the devices fitted into it are ABB for example. Every electrician has his/her own preferences on materials. Some will probably come up with missing CE, but that's not an issue here since we don't sell them on a big scale like the boards in the UK. They are custom made for the specific job, and the customer gets an instruction for operation of that board (which isn't much that the customer can actually do except switching stuff on or off), label the items and circuits properly, and of course only make them for your own jobs and then you can bypass that CE mark requirement. And just btw. : The VDE banned the new installation of type AC RCDs in 1987. Since then the type A was the standard type RCD here in Germany.

[@carlomarco1895]

Europe got the best electric boards !

[@GSHElectrical]

What an amazing explanation 👍🏻

[@NickToland]

🤯 very well explained!

[@DoctorElectricYouTube]

Great video Joe and helps explain the difference well!

[@brianwood5220]

Well explained Joe. Thanks for sharing.🎅

[@Aaron-ep1ik]

Great video thanks 👍

[@TheRaptor1122]

Shoutout to eFIXX for getting me through this apprenticeship 🤣

[@JamesCurnowElectricalEngineer]

Great video

[@DezqiNovaa]

AC RCD are banned long time ago in Switzerland if you want to know 👍🏻

[@banananaa]

In Finland it's been illegal to install type AC RCDs since 2007

[@thebamplayer]

In Germany since 1985.

[@jonathanrose456]

I’m advising most clients to wait until AFDDs become affordable before installing new circuits, etc.. IET should have made it plainer in Amendment 2 that most new circuits either require or will require AFDD protection, got the manufacturers onboard & ensured adequate supply of AFDDs at a reasonable price before the move. Absolute insanity to expect the majority of customers to pay such exorbitant prices.

[@lemech]

Is it correct to say that the DC 'leakage' current to the RCD is only on the negative cycle? Thanks;

[@therealdojj]

so where do we stand if we want to add an extra curcuit to an older board then? do we need these fancy things or can we keep to the same standard that is already in the board? or do we need to change the entire board again? having just upgraded the board it looks like we'll need to change yet again once the extension gets done next year so are we just thowing money away? thanks

[@markpotter8280]

Hhhhmmmm good question if it's a high integrity board maybe you could put the extension on a 61009 type aC rcbo or if not perhaps you could just swap out the 61008 to a type aC may as well put in a SPD and in a few months an AFDD as well if the boards big enough 🤣

[@steveclarkin6264]

You would more often than not be able to swap the type ac for a type a rcd no need to swap out board

[@richardnewton5159]

Great video, what code on a eicr would be assigned to a AC rcd on a circuit that contains DC components?

[@MrPete1664]

Personally it's a c3 from me, as testing to time it was installed.

[@markpotter8280]

@@MrPete1664 Yea it's defo a C3

[@jamesmoon5632]

What about a TT earthing system. Id code C2. Potential danger if the RCD fails and the zs is over 100 ohms.

[@tonymariner5519]

So..... all these years where I have been installing AC rdcs, they have been potentially lethal under BS7671. Does this mean I can potentially sue the IEE for incompetence?

[@mikeselectricstuff]

The issue is that the number of things that can cause DC leakage has been increasing over the years - ACs were fine when everything was electromechanical, but as most circuits are likely to have electronics of various kinds, the risk of DC leakage faults has been increasing.

[@DaveHines1]

One of the best explanations I’ve seen on this subject so far. Thanks 😃 And there’s probably a good joke here to do with second amendment rights 😉🤪🤣

[@davenoble7350]

Shouldn’t the live and neutral coils be wound opposing each other?

[@sergiofernandez3725]

What about an imersion heater in the hot water tank? That could do a type AC. I think the IET could do with a field trip up to Scotland and look at some of their regulations. Scotland seem to leed the way in some of the UK safety with regards to electrical and fire safety. I do however think that BS7671 amendment 3 will have more changes. I can see that they will push the wider use of AFDDs. It make me wonder what a customer who had a new CU/DB/Fusebox fitted lets says 2 years ago will think. Can you imagine the conversation? Your new board that was fitted 2 years ago is a split load dual rcd board, we have since gone to RCBO boards with or without SPD to the latest board with mainly AFDDs and RCBOs and a type 2 SPD. The board now cost about £1500 to £2000 that parts and labour.

[@chrisbuildelectrics4755]

I wonder for how long on future eicrs you can let a ac type rcd /rcbo go just as a c3

[@jamesmoon5632]

What about a TT earthing system.. if the rcd fails no protection

[@Marcel_Germann]

About time to get rid of them. Here they were banned 35 years ago for new installation.

[@ambiencelectronica]

Do dimplex quantum leak DC?

[@9sHenry]

What's the difference between type a and type f RCD's?

[@thebamplayer]

Look up the ABB data sheet

[@Duncan_Campbell]

How do type A or B RCDs work. Sorry not a sparky, but interesting none the less.

[@mikeselectricstuff]

They use a different type of magnetic field sensor (GMR, hall effect or fluxgate) which can sense DC without saturating

[@Duncan_Campbell]

@@mikeselectricstuff thanks

[@frankythehousecat2681]

Watch more KZbin videos & you will be a Pro !