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.
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.
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.
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
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
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.
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.
+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!
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.
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.
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 ;-)
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.
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
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.
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.
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.
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.
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 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.
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!.
... .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.
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.
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!)
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.
+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
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.
Curious to know what 3- phase supply to a residence would be in the UK. Here in the US in some situations residential installations can receive 208Y/120 service if requested, rather than the usual split -phase 120
+Kyle Shady Single phase is neutral & 230V, 3 phase is neutral & 3 phases, 400V between phases, 230V between each phase and neutral. Most residential installations are single phase, 3p is available in some areas but is rarely needed or used. Most commercial/industrial is 3 phase.
+John Ward ok thanks, the only way to get single phase 240 here is through the use of step up transformers, or step down in the case of a 480Y/277v service. I'm surprised there are actually household appliances over there that use 400v
+Kyle Shady There are no 400V household appliances - 3 phase would be used as 3 single phases where additional capacity was required, or for 3 phase items such as motors.
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.
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?...
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?
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.
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?
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.
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.
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.
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 ?
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..
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?
@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?
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.
Hi John, good video, so would the neutrals from the TOP of the RCDs go into the neutral bar on the far right as well as the neutral from the bottom of the main isolator switch and the neutrals from the BOTTOM of the 2 RCDs into the 2 separate remaining neutral bars?
16mm² typically but is does depend on the manufacturer of the consumer unit. If replacing them, they need to be the same type as specified by the manufacturer.
wait, only single pole breakers in the UK? Bit odd, i'm only used to double pole breakers in the Netherlands. Is it also normal for the bridge to be exposed like that?
+FoodOnCrack Yes, most are designed like that. Some have a plastic cover over the copper bar, but plenty do not. Double pole breakers are available here but rarely used.
can we still get the old plastic ones? I am worried about an area that is concrete wall, and has the possibility of water migration through the concrete, which to me is more dangerous than the possible fire damage... as the concrete will not burn.
They are still available, although tend to be of the type intended for wet areas so have rubber seals on the front cover etc. Most sold for use in homes now are the metal type. Installing a plastic one in a house would not comply with BS7671. it would in other places.
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.
Depends on the make and rating, but 10mm² or 16mm² is typical. If they need replacing for whatever reason, use those provided by the manufacturer of the consumer unit.
+The Spider Kelly I think it is because the circuits mostly tend to come from above so more convenient to attach to the top of the MCB. Hence busbar needs to be at bottom
Some have the live side to the left and some to the right. You would put one with the live side on the right, to the left of its MCBs (and vice-versa). This is because the busbar couldn't "jump" over a neutral without you cutting one of its teeth/tongues off.
Hi John, I know this is a fairly old video, but maybe you still monitor questions..? The incoming DP switch is rated at 100A, but do the latest regulations say what the consumer circuit loads can add up to? I mean even in your example, you have a potential load of 148A total? I know this is unrealistic, but I'd be surprised if the regulations don't have something to say?!
It's unusual for a circuit to ever be loaded to it's maximum rating for any length of time, and pretty much unheard of for all of them to be simultaneously fully loaded. Even if that did happen, the whole lot is protected by the electricity supplier's fuse, which is typically 80A or 100A, so that would disconnect the supply long before the main switch was damaged by overloading.
The inside of that unit just looks scary. Is it legal in the UK to have the busbars for phase and neutral exposed like that? (I don't consider the flimsy panel over the phase busbar decent :p)
+DJefke RBBS Thats safe compared to some of the old boards i've worked on. You literally take your life in your hands when trying to add additional circuits, or work on them. Hate the things.
Ok here is a Shocker for you :)) The Neutral will not show voltage as long as its connected to the Neutral Bar then if you take a Neutral Wire from any Circuit even the mains Neutral then test the End it is a deadly Live Wire because the Returning current has no where to go so the Neutral wire becomes an extention to the Live wire. Scary Shit ay. So don't assume the Neutral is safe ever
I have built a shed/out house on to the back of my house and I want to use the power from an existing shed which is a 6mm cable running from a 32amp fuse on the main board in the house should I put a second consumer unit in the shed or just wire it straight to the sockets and lights? If so what consumer unit should I get?
If there is already an RCD on the circuit, you could extend the 6mm cable directly to more sockets and connect lights via a 5 amp FCU. If no RCD, or you don't want to use 6mm cable (may be difficult to fit into some makes of socket), then a separate consumer unit would be required.
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.
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
To me that looks small but I'm in Canada where are panels are quite a bit larger and we have a lot more circuits. Saying that, Would that be considered a sub panel or is that the main panel?? What size of house would that panel be servicing?? Could you do a video on the different types of wire used in the UK??
+RC MAD No, ring final circuits mean you only need one power circuit per floor, so that would do a fairly normal size house (but as John says, it IS on the small size.) Example for you, a 4 bed house I worked in had 8 circuits. Upstairs power, upstairs lights, downstairs power, downstairs lights, kitchen power, Outside circuits (both lights and power, lights being fed from a fused connection unit), water heater and electric cooker
Sir your one thing i cud not understand that what is the benefit of using two RCB in one single phase distribution board?? There may be only one RCB and even it was properly worked. And if you wanna break circuit then u can do it via MCB
Hi JW, I am moving my mains and will install a new C/U. I used to swear by MK in my contracting days but to be honest I think they have cheapened in quality and not even sure if they are made in UK anymore. Have you ever come across or used BG (British General) on your jobs and if so what do you think. I used a small 6 way DB in our temporary kitchen set up at home and to be honest I thought the quality was rather good but not 100% sure if it is really entirely British. That is one reason I would now convert to BG.
MK consumer units and devices previously made in China, and now are still made in China under licence to a UK company set up to represent the Chinese manufacturer. www.circpro.co.uk/ BG are a lower priced option.
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.
+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?
+PHASKO Not mandatory, not required and never installed or even considered in domestic installations. May be considered for some industrial installations. Where installed, it's a separate module which attaches to the side of the MCB or RCD and will cause that device to trip in the event of the voltage being too low / high.
thanks for your reply. Here in Malta it should be installed maybe because of excessive flactuations in voltage. Seeing the ABB installation guide it can also serve for lightheing surges. Still I cannot understand how the 2 terminal device should be connected if alone?
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.
Clear , concise and informative. Many thanks for putting this up John . Much appreciated.
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.
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.
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.
A cam pleasant explanation and the walkthrough made it easy to understand.
Glad I came across you!
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
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.
Excellent video. I think the reason for the overhang described is so that part of the unit can be neatly recessed into a wall.
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.
Excellent and well explained videos as always. Keep doing, I know a lot of people are learning from your videos Thank you John
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.
Well done on the explanation of the buzz bar and installing it. You done a better job in comparison to ghs electrical
Well Done John it is very clear and all information needed, Thank you
JW thanks for explaining that each rcd circuit needs its own neutral bar.
RCBOS All the way, more videos on domestic electrics john, love your videos
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.
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 ;-)
Thank you Mr.JW
Excellent video as always John
Many thanks for this very instructive video, Great Work
Thank you John for all your videos, really helpful.
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.
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 ?
JW man I love you so much. Thank you
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.
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.
Thanks for putting these vids up, very helpful!!
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.
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.
Great video John.
This guy is great. I wish my electrician was as good as him!
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 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.
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!.
Best explanation regarding fuse box 👍
... .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.
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.
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.
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
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.
Curious to know what 3- phase supply to a residence would be in the UK. Here in the US in some situations residential installations can receive 208Y/120 service if requested, rather than the usual split -phase 120
+Kyle Shady Single phase is neutral & 230V,
3 phase is neutral & 3 phases, 400V between phases, 230V between each phase and neutral.
Most residential installations are single phase, 3p is available in some areas but is rarely needed or used.
Most commercial/industrial is 3 phase.
+John Ward ok thanks, the only way to get single phase 240 here is through the use of step up transformers, or step down in the case of a 480Y/277v service. I'm surprised there are actually household appliances over there that use 400v
+Kyle Shady There are no 400V household appliances - 3 phase would be used as 3 single phases where additional capacity was required, or for 3 phase items such as motors.
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.
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?...
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?
Perfect vid John, Fitting a BG metal this weekend.
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.
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.
can you show us how you personally would set one up?
You are the best sir!
One of my pet hates is rising clamp terminal blocks like this that leave a gap beneath the clamp.
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.
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.
Circuits power for gas cooker power ratings? How do you know which rating is required
very helpful as always very well explained john Thanks
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.
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.
Hi, what’s the name of the terminals for flexible wires, I’m just from another country, and I can’t find them
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"
Hi John, what size are the main cables coming into the cunsumer unit?
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..
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?
@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.
Excellent explanation
Hi John, good video, so would the neutrals from the TOP of the RCDs go into the neutral bar on the far right as well as the neutral from the bottom of the main isolator switch and the neutrals from the BOTTOM of the 2 RCDs into the 2 separate remaining neutral bars?
Panasonic HC-X900, now discontinued. The X920 is the current equivalent.
What size are the neutral cables that supply the rcd's and then to the neutral bars.
16mm² typically but is does depend on the manufacturer of the consumer unit.
If replacing them, they need to be the same type as specified by the manufacturer.
Thank you John. I am so very grateful for your excellently presented videos.
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
wait, only single pole breakers in the UK? Bit odd, i'm only used to double pole breakers in the Netherlands. Is it also normal for the bridge to be exposed like that?
+FoodOnCrack Yes, most are designed like that. Some have a plastic cover over the copper bar, but plenty do not.
Double pole breakers are available here but rarely used.
+John ward can can you do a video on cable sizing.working out the tabulated current carrying capacity
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.
can we still get the old plastic ones? I am worried about an area that is concrete wall, and has the possibility of water migration through the concrete, which to me is more dangerous than the possible fire damage... as the concrete will not burn.
They are still available, although tend to be of the type intended for wet areas so have rubber seals on the front cover etc.
Most sold for use in homes now are the metal type.
Installing a plastic one in a house would not comply with BS7671. it would in other places.
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.
Nice video John, thanks for sharing.
Whats the CSA of the cables going into the RCD's
Depends on the make and rating, but 10mm² or 16mm² is typical. If they need replacing for whatever reason, use those provided by the manufacturer of the consumer unit.
What is the reason besides convience in some circumstances, for wiring the live bottom to top for the MCB's?
+The Spider Kelly I think it is because the circuits mostly tend to come from above so more convenient to attach to the top of the MCB. Hence busbar needs to be at bottom
+whitefields5595 Ah ok, thanks for the info.
How about the in and out sides? Is there any requirement for RCD that which side should be in?
Some have the live side to the left and some to the right. You would put one with the live side on the right, to the left of its MCBs (and vice-versa). This is because the busbar couldn't "jump" over a neutral without you cutting one of its teeth/tongues off.
is there a sprit-level on bottom of that fuse box? or is that just me seeing things.
+scaleop4 Yes, spirit level is included.
+John Ward And by all accounts it's all but useless.
Hi John, I know this is a fairly old video, but maybe you still monitor questions..? The incoming DP switch is rated at 100A, but do the latest regulations say what the consumer circuit loads can add up to? I mean even in your example, you have a potential load of 148A total? I know this is unrealistic, but I'd be surprised if the regulations don't have something to say?!
It's unusual for a circuit to ever be loaded to it's maximum rating for any length of time, and pretty much unheard of for all of them to be simultaneously fully loaded. Even if that did happen, the whole lot is protected by the electricity supplier's fuse, which is typically 80A or 100A, so that would disconnect the supply long before the main switch was damaged by overloading.
? listening to you say that you fuse the Neutral wire. we don,t do that in the US.
The inside of that unit just looks scary. Is it legal in the UK to have the busbars for phase and neutral exposed like that? (I don't consider the flimsy panel over the phase busbar decent :p)
+DJefke RBBS Yes, most are constructed like that.
+DJefke RBBS Thats safe compared to some of the old boards i've worked on. You literally take your life in your hands when trying to add additional circuits, or work on them. Hate the things.
Some have plastic covers for the live busbar. Neutral connectors block/s is always exposed.
Ok here is a Shocker for you :))
The Neutral will not show voltage as long as its connected to the Neutral Bar then if you take a Neutral Wire from any Circuit even the mains Neutral then test the End it is a deadly Live Wire because the Returning current has no where to go so the Neutral wire becomes an extention to the Live wire. Scary Shit ay.
So don't assume the Neutral is safe ever
ths s the most helpful video i ever watched, thnx sir
Hi, where do we get the brown twin crimp which is on the top of the first RCB, I really need to buy that.
For one or a small quantity probably ebay or similar - the thing to search for is 'twin cord end crimp'.
I have built a shed/out house on to the back of my house and I want to use the power from an existing shed which is a 6mm cable running from a 32amp fuse on the main board in the house should I put a second consumer unit in the shed or just wire it straight to the sockets and lights? If so what consumer unit should I get?
If there is already an RCD on the circuit, you could extend the 6mm cable directly to more sockets and connect lights via a 5 amp FCU.
If no RCD, or you don't want to use 6mm cable (may be difficult to fit into some makes of socket), then a separate consumer unit would be 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.
What make of 30mA 40A 4P RCD do you recommend?
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 !!
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.
To me that looks small but I'm in Canada where are panels are quite a bit larger and we have a lot more circuits.
Saying that,
Would that be considered a sub panel or is that the main panel??
What size of house would that panel be servicing??
Could you do a video on the different types of wire used in the UK??
i think that panal would probably be for a flat or small cottages
+RC MAD No, ring final circuits mean you only need one power circuit per floor, so that would do a fairly normal size house (but as John says, it IS on the small size.)
Example for you, a 4 bed house I worked in had 8 circuits. Upstairs power, upstairs lights, downstairs power, downstairs lights, kitchen power, Outside circuits (both lights and power, lights being fed from a fused connection unit), water heater and electric cooker
meh
+RC MAD yep that was my reaction, not enough room for expansion.
expansion is no go
Sir your one thing i cud not understand that what is the benefit of using two RCB in one single phase distribution board?? There may be only one RCB and even it was properly worked. And if you wanna break circuit then u can do it via MCB
There are two so that if a fault occurs, it doesn't disconnect power to the whole house - each RCD only covers half of the circuits.
John Ward It would also reduce the frequency of nuisance tripping, yes?
Hi JW, I am moving my mains and will install a new C/U. I used to swear by MK in my contracting days but to be honest I think they have cheapened in quality and not even sure if they are made in UK anymore.
Have you ever come across or used BG (British General) on your jobs and if so what do you think. I used a small 6 way DB in our temporary kitchen set up at home and to be honest I thought the quality was rather good but not 100% sure if it is really entirely British. That is one reason I would now convert to BG.
MK consumer units and devices previously made in China, and now are still made in China under licence to a UK company set up to represent the Chinese manufacturer. www.circpro.co.uk/
BG are a lower priced option.
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
Hi jw . Reg: Consumer units .
What brands are the best / easy to install cable / arrangement- Rcds + . And
A garage unit (c.u ).
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?
thank you for your incredible movies. any chance of doing one about insulation testing? any point trying to do insulation testing with an ohmmeter?
Do you have any clip showing o/uvr connection to the cu? Is O/Uvr installation mandatory in the uk? Is it difficult to install it?
+PHASKO Not mandatory, not required and never installed or even considered in domestic installations. May be considered for some industrial installations.
Where installed, it's a separate module which attaches to the side of the MCB or RCD and will cause that device to trip in the event of the voltage being too low / high.
thanks for your reply. Here in Malta it should be installed maybe because of excessive flactuations in voltage. Seeing the ABB installation guide it can also serve for lightheing surges. Still I cannot understand how the 2 terminal device should be connected if alone?