Dual RCD Consumer Unit
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- čas přidán 27. 08. 2024
- A look inside a typical dual RCD consumer unit as used in the UK.
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Mr Ward your videos are better then evening classes. Your videos are really a full course in electrical installation.
John I’ve been an avid follower of yours for a very long time. Not only are you exceptionally knowledgeable, you provide clear and concise explanation that the view is able to understand apply to their own given situation. I’m very grateful and enjoy looking forward to new videos as and when you post them. Again, thank you!
Outstanding! If I'd had a teacher like you at school I might of done something with my life instead of skiving off and wasting the chance of a decent education.
The bus bar tip is brilliant thanks so much for explaining it so clearly. I’ve just checked this on a new consumer unit and one leg was wrong side of the slot! Who’d have thought eh? New out of the box too! Respect
John.. A very well explained video. yours is by far the best explanation of this topic I have found to date. Thank you for taking the time to create this.
I have a 1970 house. I had the Wylex box replaced when I moved in because my surveyor red-flagged it. The lights are all on one circuit, and the sockets are all on another. The electrician put them on the same RCD. So now, if I trip my sockets at night, all the lights in the house go out. Genius!
Another video said downstairs sockets and upstairs lights on 1 RCD, and opposite for the other RCD...then if there's a power out there is still at least residual light. Or just RCBOs like this no nonsense man says
I feel like I should leave electrical work upto the experts, but then when you look at some so called experts work, it makes you glad people like this man put these videos out there so we have a chance of putting things right
Your electrician has no common sense, If one breaker or fuse trips you have no light, He should have split the lighting in two.
@@chestermartin2356 That is why I do as much work myself as I can. Then I know it is done to the standard that I want.
Just about to fit one of these new plastic CU myself - bringing greenhouse, shed, garage and cellar together, which are then connected to the house, so thank you for your clear explanation, it is a great help.
Just Excellent!!! Just what I needed. I'm installing an automatic transfer switch for my back up generator and I don't know how to wire it, this has been a great help. Thank you
Excellent video. I think the reason for the overhang described is so that part of the unit can be neatly recessed into a wall.
Hi there John thank you for the instruction on the consumer unit I've just replaced my old unit with a modern one but it kept tripping when I plugged any think in. It was just a case of the neutral wires it the the correct bus bar. Cheer's Jon.
JW thanks for explaining that each rcd circuit needs its own neutral bar.
A cam pleasant explanation and the walkthrough made it easy to understand.
Glad I came across you!
Excellent video as always John. This is certainly a lot better than having no RCD's at all like so many older houses in the UK. I replaced my old MK fuse board with one of these last week and it started tripping due to a borrowed neutral. Thanks to you I knew exactly what was happening. Thanks and keep up the good work.
+hyperion8008 As changing a CU is notifiable how did you deal with it?
+Graham Langley in your own home.... who cares? I'm a electrician by trade and if I installed it in my own home I wouldn't do any certification at all!
+tittytwister5251 An 'electrician by trade' who didn't know about borrowed neutrals until they saw John's video?
im not the original poster of that comment... of course i know about borrowed neutrals..
+tittytwister5251 Oops - sorry.
Our house has a much older consumer unit from the early 1980s with bottle fuses. I think it's 4 x 6A for lights, 4 x 16A for sockets, 1 x 40A for the shed welder outlet and 1 x 65A master fuse. It has an 30mA rated chunky RCD that covers the sockets only and it is surprising the range of appliances that developed an earth fault over the years. Thankfully not many appliances go short circuit as replacing a bottle fuse is not fun, particularly if an appliance/lead develops an intermittent short.
Great vid, as always *JW* - I've found that heatshrink can be cut and 'rewelded' using cyanocryolate... Carefully done, those copper Line (L) bus plates could be shrouded in brown heatshrink if a cover was not existent.
Well done on the explanation of the buzz bar and installing it. You done a better job in comparison to ghs electrical
Thank you Mr.JW
Excellent and well explained videos as always. Keep doing, I know a lot of people are learning from your videos Thank you John
RCBOS All the way, more videos on domestic electrics john, love your videos
Well Done John it is very clear and all information needed, Thank you
This guy is great. I wish my electrician was as good as him!
Excellent video as always John
Interesting. We have RCDs built into some of the sockets which protect any sockets down the line from them. Required by our NEC for kitchen, bathroom, and outdoor sockets. We also have breakers with built-in RCDs, but as you said they are very expensive. And of course being that we use both 120v and 240v, we have different breakers for 120 and 240. Our main switch is required to be a breaker, just in case the individual breakers that have been fitted are loaded up as such that they are not individually overloaded, but combined exceed the mains input (typically 100, 150, or 200 amp for residences)
***** the most powerful home kettles are 1500w here. Although I did find a KitchenAid 3000w, it was 230v which we would have to install its own socket in the kitchen. Not very common though, most people in the US generally have only a small stovetop teapot, or use the coffeemaker for hot water. We're a bit strange ;-)
Many thanks for this very instructive video, Great Work
Interesting, in germany we have light and sockets connected to the same breaker, but we have a breaker for every single room.
Also we have 3 phase design for high power applications. Nice to know.
Daft idea really, if you lose that circuit then all your lighting, table lamps everything goes off. Could be quite dangerous actually.
Thank you John for all your videos, really helpful.
Thanks for putting these vids up, very helpful!!
Best explanation regarding fuse box 👍
Perfect vid John, Fitting a BG metal this weekend.
WoW, here in Belgium they're a lot bigger, mine is even a floor model that is 2 meters in height... (But then I'm an electrician, so that's more geekiness I think)
+Joy Van Acker Yeah, I think much of the EU has it much better than we do for design. While there are sufficient circuit ways, the amount of wiring space is TINY, not conducive to neat workmanship. It CAN be done but it's a lot more effort than it would be on a larger panel. Does Belgium follow what many EU countries do and have 3 phase 230/400v into the house/flat? That could explain the larger size too, keeping separation between phases? (guessing!)
+TheChipmunk2008 Here in Belgium you can choose betwoin 1f230+N, 3f230 or 3f400+N, that will give you larger panels also. But it's like you're saying, making your installation future proof by installing enough circuits is key I think. And neat cabling/installation is always a must! :-)
+Joy Van Acker Thanks for the fast response, yes, you can tell a true craftsperson when you see them take that little extra time to make things neat.
Incidentally, the 3phase 230v without neutral you speak of, is that the old 127v to ground with 220 between phases that much of Europe used to use?
(Which also freaks out younger people with old stereo gear wondering why it has such an odd voltage option on the selector, 127v!)
+TheChipmunk2008 That's correct, 3f230 is 230v between the phases, 3f400+N is 230 between phase and neutral and 400 between phases.
One reason why they are bigger in Belgium is because 2 pole breakers are mandatory (or more if 3f or 3f+N). Even N must go thru the breaker. Also your light and sockets must be kept separate (exceptions are possible) and the number of sockets per breaker is limited. Even in a smal house or apartment you will often need a 2x12 modules or more.
Great video John.
Another great video JW, thanks. I'm surprised those un-insulated live bus bars are still allowed - in this day and age of health & safety.
Some makes have a plastic cover to clip over the busbars, however many do not.
Not really a problem as the main switch should be off before removing the cover.
You are the best sir!
JW man I love you so much. Thank you
Why is that panel designed with 2 extra spaces to the right, out of interest? It looks like with an alternative cover the main switch could move 2 positions to the right, so as to allow the board to easily take 2 further breakers (e.g. 2 RCBOs to complement the 2 small RCD groups), not too bad a config at all if carefully thought out layout.
Excellent, just what I needed thank-you! Just got back from Screwfix with the exact same model of CU - but metal of course.
Great video, really helpful, thanks for taking the time to post up.
John, also can you do a video on just how many times a solid core wire can be disturbed inside a patress box, or CU, before it breaks. What is the fatigue characteristic of a solid copper core and how can that fatigue life be extended without annealing or some other form of heat treatment.
Nice video John, thanks for sharing.
... .and just to complete it include steel and brass screws onto copper wire. Copper wire necking creating a fracture point. Screws loosening inside (concealed) junction boxes. Comparison between steel and brass screws, perhaps stainless too. The ideal method for soldering copper cores together. I'll show you mine, if you show me yours.
very helpful as always very well explained john Thanks
British General brand.
When testing an installation with one of those consumer units fitted, I found that the RCDs were adding about 0.5 Ohms to the Zs figures. It made a couple of circuits only borderline pass.
Strange, I've never found any other brands with such a problem.
Anyone else encountered this?
There's something very strange about that. I, say, 20 amps was flowing through an RCD with a 0.5 ohm resistance, then the power dissipation would be 20 x 20 x 0.5 = 200 watts. Naturally 200 watts dissipated in an RCD (or in a CU in total) would be disastrous. If the current from a 10 kW electric shower passed through it (about 40 A), then that would be 800 watts.
Excellent explanation
Hey JW. Great video - you mentioned your preference for RCBO units. How about doing a video about the internals of an RCBO consumer unit? It would be interesting to see the difference in wiring regimes as I would assume each RCBO would need their own neutral connection. Cheers
+Bob Fish
Look them up, there are loads of images... its' really simple -- main switch feeding line busbar into the RCBOs, then all the flying neutral leads go back to a neutral bar... Each circuits' line+neutral connections go directly into output terminals on the RCBO. Simple... There are many videos on fitting those, too!.
Hi ,
thank you for all your great videos. can you tell be the best practice to extend cables to a new consumer unit 3 metres away. All cables are required to be extended.
thanks in advance
Adaptable box with all connections ?
Nice layout
Cheers, Very helpful and clear.
+Adam Day If i was to put an extra rcb between the main switch as you stated for the Fridge freezer i.e if something trips the main ring I assume the 'singlr rcb would be okay for the Fridge freezer. Also how will the from fit on?
One of my pet hates is rising clamp terminal blocks like this that leave a gap beneath the clamp.
Really useful. Thanks.
ths s the most helpful video i ever watched, thnx sir
Nice work sir
we have an older type of consumer unit with one rcd protecting all rcd protected circuties and we have a switch under the consumer unit which when it trips all our electric is cut off we once had a boiler pipe leak and early in the morning the fuse under the consumer unit tripped and we was in a house without electric early in the morning when it was still dark it was winter i think at the time.
Yes, and that's the problem with single RCDs. My preference is to use RCBOs. The way each circuit has it's own residual current protection so only that circuit is lost in the event of a fault and, as a bonus, it's easier to fault find.
Retrofitting RCBOs is relatively simple, albeit that the box can get a bit cramped with the extra wiring involved and the larger devices, albeit that two slots are gained. The other issue is the cost, but as an installation is likely to be there for decades, it's not a ridiculously expensive job.
can you show us how you personally would set one up?
Very good, very clear!
Thank you!
Hi, If my garage is already being fed via an RCD in my house, does that make the RCD (it's been there since before we moved in) in the garage redundant and I could just have a "main" switch and MCBs?
If the RCDs are the same type, then you only need one in the house
There are situations where two may be required, such as a 100mA time delayed RCD in the house and a 30mA RCD in the garage.
@@jwflame got It, thank you for your reply. Just had a look inside RDC in the garage (it just an RCD in a metal box which then goes to an old consumer unit) and it's only got a line and neutral, no earth and no earth ring so as to use the armour as earth. Thank you again.
It is fascinating to see how different the electric distribution panels are in the UK ("consumer unit") and US ("load center"). Very surprising to see that the UK unit is basically just a plastic box with a DIN rail inside it. I do like the rails, actually, because it eliminates the need for bussing.
I see everything is on the same line there. Are there any installations with split-phase power in the UK or is it typical to receive only a single leg of the circuit?
The majority of homes have single phase 230V, supplied as two wires, a neutral and 230V.
For anything larger you get 3 phase & neutral, 230V between each phase and neutral, 400V between any two phases.
No need for anything else as all appliances are 230V.
What is that 2 into 1 peice called that links the RCD's. I have a board where the cable is pushed in with the bus bar at the bottom. Should be going into a y peice like that.
Bootlace ferrule or pin crimp. However to fit them requires the proper tool, which isn't particularly cheap. Some consumer unit manufacturers also weld the wire ends together so that they are a solid piece.
If it's not using the correct wire, it will be cheaper and easier to just get a replacement cable set from the consumer unit manufacturer.
Do not suppose you could possibly do a video segment covering Din Rail Surge Protective Devices (SPD's)? I am curious and also now does appear to make reference in the new wiring regs 18th edition draft. Cheers.
John, Can you do a video on the use of torque set screwdrivers on the terminals please?
+whitefields5595 FWIW the CU here got changed recently and the sparks went round every terminal with his torque driver. Next day I checked them all. About half were still OK, most of the rest less tight than I'd like and a couple were now actually loose.
+Graham Langley ... indeed, I found similar, hence the question. It is almost as though you have to overtighten to make sure everything is seated, then back right off then tighten again to the right torque. Or at least that's what I do, but I do not use a torque set screwdriver
Hello,
If you had three RCDs in a consumer unit, would you have to introduce a bus bar for live wires and then from bus bar go with live wires to each of the three RCDs? Or is there any other way going about it?
Yes, it would also require 3 neutral bars, one for each RCD.
Far easier to just install RCBOs.
@@jwflame
Understood. Thanks.
Many thanks great John
When choosing an RCD, does it have to be equal or larger(Amp-wise) than the MCB's connected on its circuit, does it have to be equal to the Main Switch?...
Is it necessary to have a split board my dad has an old fuse board I want to replace and he has 1 lighting and 1 ring for the whole house can you still get a fuse board with mcbs and 1 rcd rather than a split load cheers?
You can have pretty much any combination of devices, just by buying an empty enclosure and suitable items to fit into it.
For only 2 circuits, a main switch and 2 RCBOs would be ideal.
well explained thank you
Excellent video, thank you !!
great explanation , thank you Sir
I would like to see a 2021 version of this video as now I'm advised (still not done 18th Ed due to Covid) that each circuit requires an RCBO now and a anti surge device.
I have googled 18th Edition complete C/U's and I haven't as yet found one that has all this stuff, just the same ones as you were using in this 6yr old video.
The 18th edition OSG states that such an arrangement (i.e.2 RCDs in one CU) is "Generally [...] not suitable for an installation forming part of a TT system as there is insufficient fault protection of the single insulated conductors which connect the load side of the double-pole main switch to the supply side of the RCCB." (p.37 in relation to Figure 3.6.3(ii) on p.36). I am not sure I understand why this is so. I would have thought that if there were a problem with a 2nd RCD there should also be a problem with RCBOs. I would be very grateful for your thoughts on this matter. Thank you.
The supply side conductors are not protected by the RCD, and on a TT system the earth fault loop impedance will be high, so a fault between line and earth will not blow the main fuse.
It's more of a problem with dual RCD efforts because they have single insulated flexible wires from the main switch to the RCDs, and one of those being damaged could make contact with the earthed metal case of the consumer unit.
With an all RCBO board, line is on a solid fixed busbar so very unlikely to cause a fault to earth.
However for all TT installations, there is still the possibility of a fault between the incoming line and the metal case of a consumer unit, there are various plastic glands and similar which are intended to avoid that happening. Or an time delayed RCD could be fitted before the consumer unit, although that can lead to other problems such as when used with single pole RCBOs.
Excellent video Thanks
Love your videos, John. I am confused about why you can jump line wires from main switch to the two RCDs. I think from main switch to RCDs, there should be separate feed.
That isnt necessary as your not separating anything.
Is the ground/earth bar connected to the neutral bar at the back of the Unit? I found on the board of my house, the neutral In and Out from RCD is connected to the a single neutral bar, and so are other sub-circuit neutral. is the correct wiring?
No, neutral and earth are completely separate within the consumer unit.
If both neutrals from the RCD are connected to the same bar, the RCD won't work.
@@jwflame when I disconnect the eath bar from neutral bar, the RCD did not even switch on. so I have to connect the ground/earth bar back to the neutral bar and take the neutral from that to feed in the RCD, then RCD neutral and all sub circuit neutral are connected to a separate neutral bar. it seems to work, Test button works fine. but still not sure If I have done it correctly as it does not look like what you showed in the video. The whole reason for me to look at and redo the wiring at the board is that the RCD went off when I recently reconnected an old circuit back into the board and after checking the wiring I realized that the RCD was weirdly connected, serving only single circuit that I reconnected. ant thought ?
@John Ward I guess the circuit in our house is so called "grounded neutral"
Is the UK banning plastic boxes? What's the reasoning behind that? I mean, the plastic you've got there looks flimsy and thin, but in principle I think I'd rather have my mains stuff in plastic than in metal...
Since January 2016, they must be 'non-combustible', with an example of that being steel. No other examples are given and no definition of 'non-combustible' is provided either, so in practice they are all steel now.
This only applies in homes, commercial and industrial ones can still be plastic, however they are typically metal anyway and have been for decades.
Bakelite is pretty non-combustible. Maybe some of the fuse box manufacturers still have their machines from fifty years ago.
b.
The answer is twofold. Firstly, in most domestic applications, the consumer unit is sited either under stairs, or in entrance hallway. This causes major problems in the event of a consumer unit fire, and increases the risk of not getting out of the property. Sadly, it appears that it is also widely accepted, that the standard of installation in consumer unit replacement leaves much to be desired. Price work, fast track project delivery, and no quality control, means the shite standard will continue as the norm. This has more or less been said, without saying it! Introducing something which doesn't melt and keep burning is a sad way to have to combat it. Obviously it must be easier than raising installation standards.
Brilliant. So clear that I'm determined to install my own myself. But is it still legal in the UK for a handyman (aka recreational electrician) to install a pre-wired consumer unit, rather than a qualified electrical tradesman. Fortunately I have installed one previously under the supervision of a qualified electrical tradesman so your refresher is much appreciated.
the cable from the bottom of the isolating switch then goes to the top of the right rcd. what is the thing called at the top of the right rcd that then sends the cable to the top of the left rcd?
Excellent!!
Fantastic. Thank you! 👍👍
Job well done
Hi JW, I have exactly the same this CU and it's wiring type as the main and only one panel in my small house, so where can I bond neutral and ground together?
That consumer unit is intended for use in the UK, and in the UK it's not permitted to connect ground and neutral anywhere within the installation.
Other countries have different rules.
@@jwflame
thanks for answering,
If live wire touched metal case of the load then how MCB would trip? What is grounding system used in this circumstances?
Why the neutral bar and the earth bar are not connected together ?
Not permitted to do so.
@@jwflame Looks like that each country have their own regulation !!
Hi, what’s the name of the terminals for flexible wires, I’m just from another country, and I can’t find them
What make of 30mA 40A 4P RCD do you recommend?
Well explained thank you .
If you were to install an 8, 8.5, 9 and 9.5KWshower could you wire them on a 32a mcb with 6mm cable or something else. because 9500/240=39.5A, and 6mm cable is rated at 47 clipped direct. Also, an MCB doesn’t trip exactly on the rated current does it?
6mm cable is ok, but a 32A MCB is only suitable for a 7kW shower, anything above that will require a higher rated MCB.
Although MCBs to not trip on the exact current, running them at overload all the time will cause them to overheat and eventually be damaged.
Continuous load must be smaller than the MCB rating, and the MCB rating must be smaller than the cable capacity.
@@jwflame ah ok. So to do a 9.5kw shower I could do it off of 6mm cable, but would the mcb be either 40A or 45A?(if not protected by RCD, install RCBO). Because 9500/240=39.5A, and 6mm is 47A rated, so the the load would be much under the cable rating.
Thanks johan
How about doing a more expensive consumer unit that is "not usually sold in diy sheds" as you put it.
There isn't a massive amount of difference with them. They usually just fit together in a nicer fashion, look better and have fewer RCD's fail. The actual wiring inside is the same and they physically are no different.
they all have to meet strict regs
Circuits power for gas cooker power ratings? How do you know which rating is required
Does the new code require all to be rcbos and no longer requires dual rcd?
It doesn't specifically require that, but what is needed is 'Every installation shall be divided into circuits as necessary to avoid danger and minimize inconvenience in the event of a fault'
and with RCBOs being readily available, using a dual RCD arrangement doesn't meet that requirement.
thanks for this
Can anyone tell me why the Lives are daisy chained from the master switch to both RCDs but the neutrals go to a bus bar and then the RCDs.
Gives the option of adding one or more circuits with no RCD, they would connect to that neutral bar, and to another short piece of busbar from the bottom of the main switch..
Electrically it would be identical if the neutrals connected directly to the RCDs
@@jwflame Ah...that would make sense. Thank you.
@John Ward What is the general cause of a main incoming rcd tripping even when ALL the individual circuit breakers are off? Is that still likely to be an Neutral to earth fault as the lives are all disconnected?
Yes, N-E fault on one or more of the circuits. You will need to disconnect the wiring for each circuit and test individually.
John Ward Turned out to be a fried main 100A rcd. Dead short on Live/Neutral on the outgoing side! Curious what would cause that to happen. All circuits tested ok before the replacement was fitted.
Bare copper plate for live connection between rcd and breakers, didn't think that would be allowed..
+John ward can can you do a video on cable sizing.working out the tabulated current carrying capacity
Hi Jw. , need to move consume unit by about 3ft ! What is the best and safest way to extend cables. Can you advise me please . Mark
Super! Many thanks.
Nice sir
It's a helpful video.
Hi John great video, what would cause the RCD to have burn marks at the bottom? Electricity trips but no fuses or RCD actually trip?
Almost certainly loose connections, which cause overheating.
Does it need MEN link between neutral and earth bars?
No, and in the UK such a connection is not permitted inside the consumer unit.
I was thinking the same thing, in Australia there is a link, but we do not use the dual type CU...all lighting and power outlet now has to have RCD or RCBO protection..
thank you. really helpful.
John has some good knowledge on Circuit Panels. If I could ask him to speak up a bit and try not to mumble, that would be excellent. Looking forward to more videos from John.