EXTENDING CONSUMER UNITS. How to add a second consumer unit to an existing circuit.
This video is about adding an extra consumer unit to an installation.
It happens sometimes, that a customer will ask for a new circuit to be installed for a new shower, or a new electric cooker circuit to replace the gas cooker, perhaps a circuit for a new extension that has been built or maybe a request to add power and lighting to the garage.
And then, on inspection it is found that there are no spare ways in the existing consumer unit.
Rather than replace the whole consumer unit with a new and bigger board, an option that can be taken is to add a second consumer unit (sometimes called a mini consumer unit or garage unit).
This will mean breaking into the existing wiring, and so how can this be achieved correctly and safely.
This video will go through the steps in detail and will guide you in making a safe addition to the existing installation.
Remember that electricity is dangerous. Always lock off and carry out safe isolation before working on electrical circuits. If in doubt, stop and seek advise from a competent electrician.
To view all our videos, click on the following link
/ @learnelectrics4402
SEE ALL - To view a list of all our LearnElectrics videos, click on the link below. There are many videos on many electrical topics including Installation, Part P, 18th Edition, Testing, Certification, Lighting, Sockets, Ring Circuits and much more. kzhead.info/tools/YaJQnpO4XAp0yCgqzMkmfA.html
Again another excellent video, clear and so easy to follow. I can tell, you have put a lot of hard work into preparing these videos, and it shows. Thank you.
Thank you very much Frank, really appreciated feedback. Dave.
Best explanation on YT. As usual it's the official part, ie getting energy company to remove and install fuse that could be viewed as a problem 😅.
Thanks for the great comments. Appreciated. Dave.
Just came across your channel. I am really enjoying your videos and your calm, very explained manner in which you teach. Thank you
Awesome, thank you, really appreciate the feedback. Thanks for watching, lots more to come, Dave.
Perfect. Validates how I've planned to provide power to a new garden room. I will be getting a qualified electrician in as it's notifiable works, but now I know my suggested method is sensible.
Brilliant. Glad the videos helped. Good luck and take care Gary. Dave.
You are very clear in your teaching. Good stuff
Great feedback, thank you very much. Dave.
Thanks for you're channel. Just discovered it and halfway watching this video I immediately subscribed. Lookin forward of watching all of youre videos. Kerp them comin. 👍
Thanks Jexi, appreciate the feedback and glad you have subscribed, there are more than 50 videos so far, lots more to come and Monday's video will be about 2 way split load consumer units. Dave.
@@learnelectrics4402 thanks Dave. Ure videos are no nonsense. It's therapeutically informative for a competent person. Thank you & dont want to miss you're every Monday post. Stay safe and keep em comin. 👍
Great stuff.
Always great advice and very clear
Thanks for the positive comments. Dave.
Very clear and easy to understand for every level!! This is the best learning youtube chanal for Electrician!! Thank you!!!
Wow, what a fantastic comment. That has really made our day. Thank you so much. Bux
@@learnelectrics4402 🙏🏻
Thankyou for the positive feedback.
Is there any chance to make a video about Different tests and techniques? And Fault Finding methods? Honestly this is the far better video channel so far I see on KZhead! Thank you again🙏🏻
Yes, we are making videos on the different tests, completing test certificates and common faults with tips on how to find them. Keep watching, they are coming. Thanks for the very nice comments, we do appreciate your feedback. Dave
Thanks again for the great explanations, Now why can not we have our electrical installations simplified like you do. Its easy to understand and makes sense. I am an old Canadian electrician and always wondered who made our code book so complicated. Thanks again
They are written by the White Coats as I call them Lyle. But in truth, I wouldn't fancy writing 600 pages plus of Regs. Let them write them and we will interpret them. Good Luck. Dave.
Yes, it is the same in the UK but it is all to do with business , this is how they do it to make money. And this chanell is the best chanell actually.
Brilliant explanation 👍🏼👍🏼👍🏼
Happy that we could help. It makes all the effort worthwhile. Dave.
Easy explanation , well done 👏
Glad it helped. Dave.
Another excellent video-thank you
Thanks David, thank you for watching. Dave.
@@learnelectrics4402 Thanks Dave, I’m retired now, but began serving my time, in 1974--only wish these resources were available back then, but we still managed- I don’t practice any more, but still do minor work for friends and family-- Its great to see all “ the young people” showing us the work they are doing on you tube. Again many thanks, and keep on doing what you do-
Thanks David. I started in 1976 and I totally agree about all the help that's available now. We had almost nothing then and the only way to find out information was the bookshop. I just caught the end of the valve era and the start of logic circuits. Does anyone remember Norbit logic now. Some good memories. Thanks for watching. Dave.
Another great video... Thankyou
Thank you, your positive feedback is truly appreciated. Glad you like our videos, your feedback makes it all worthwhile. Dave.
Excellent video again 👍
Thank you Mark. Your positive comments are very much appreciated. Dave.
Thank you very help full It is well explained
Thanks for the great reply. lots more to come. Dave.
Just passed the 18th edition thanks to you on the 26.06.21
Great news Andrew. If I helped in a small way then that is good but you did this yourself because you bothered to learn. The secret now is to keep adding to your knowledge until it becomes internalised, until it is no longer a struggle to remember things. Keep watching the videos, lots more to good stuff to come. And spread the word about the channel, it might help others to pass. Good luck with your career, its a great trade to be in and its taken me around the world several times. Dave.
Great video. Thanks
Really happy that you like it. Lots more to come. Thank you.
Loved it thank you
We are so glad you like our videos and thanks for the positive comments, they all help. Bux
Great video, thank you
Thanks for the positive comments, we do appreciate them. Bux
Very informative, please keep them coming.
Thanks for the great feedback. Yes, lots more to come.
@@learnelectrics4402 really appreciate you sharing the valueable knowledge which is complete as most of electrical videos are shared but not complete as some parts are missing. Thanks
Well thanks very much, we really appreciate your positive comments. We try to be different and tell you what you need to know to be good at your job. Lots more to come, tell your mates about us, it all helps. Dave
@@learnelectrics4402 thanks and afcourse, looking forward to more content cheers
Thank you and yes, lots more to come.
Excellent videos, electricity companies are very annoying they come and install a new electric meter in the property but cant be bothered to install an insulator switch at the same time.
I know Mike, several have noticed that. Glad you are enjoying the videos, thanks for your support. Dave.
Superb, many thanks as always for these uploads 🥃🇬🇧
Thank you for the positive comments, they really do help. More to come. Dave
Thanks Dave, another great video. Keep them coming. Can you do one which shows how to fit an rcd unit into an older consumer unit after installation of a i.e extractor fan into a bathroom.
Yes, why not. We will see what we can do. Give it a couple of weeks and we will put one together. Thanks for the encouraging feedback. Dave
@@learnelectrics4402 Thanks mate. I'll keep an eye out for it.
No problems. We will definitely be doing one. Watch this space. Thanks. Dave
@@learnelectrics4402 thanks mate!
You're welcome.
Very clear description. What is the situation with for example, having a small shower or garage "fuse box" with a 2 or 3 kw load, on the end of an existing 6mm2 T&E running from a 32A MCB in the main RCD protected box. Rather than directly from meter tails & Henley splitter block/s? Is this a problem? Should the small fuse box also be RCD protected or does this cause problems, having an RCD running off an RCD? Should a simple 2 pole isolator type of main switch be used on the small extension box & rely on the 32A MCB & Main RCD?
If the existing 32A supply is RCD protected that is fine. The garage unit, I assume will be an RCCB plus 1 or 2 MCBs, this is quite normal. If it was me I would use a 20A mcb in the garage unit and run the sockets as a radial circuit and 6A for lighting. Thanks for watching. Dave.
Good video and thanks. Can you comment on sub mains longer than 3m to a second consumer unit in, say, a new extension. Is protection against overcurrent and fault current required on the output side of the Henley block? The On Site Guides are not much help, the IET Forum reigns confusion and Chapter 43 of the 18th is bewildering! Any insight would be appreciated. Thanks
Some DNOs like you to fuse/RCD at both ends of tails that are greater than 5 metres in length. A definitive answer is hard to find, all they say is to keep them as short as possible and be reasonable about the length if it does need to travel some distance.
Excellent video again, although I would check that the meter tails are large enough if the fuse cutout has to be increased, otherwise replace with larger tails (or does the electricity supplier do that!?
Thanks Robert, good feedback and really appreciated. Usually it is the electrician that will supply the larger tails for the DNO to install if they upgrade the main fuse. Covered in a different video. Great to have you along and loads more to come. Dave.
Great video as always, I really wish id had access to this level of information when I was doing my apprenticeship. I have a question too, im replacing a dual tariff CCU and the tails on the economy 7 side will not be long enough for the new unit (Iv had to buy double stacked). Can I use henley blocks within the CCU to extend the tails? There is no scope to rewire the existing tails as its in a block of flats. I just wondered if it was okay to extend them like this and have the henley block inside the unit? Any help or advice is greatly appreciated. Cheers
Thanks for watching Kev and yes I totally agree. Where was the internet in the 70s when I was training. Henly blocks no problem, that is the standard way to extend. I used to torque the blocks up and then return to them after an hour or two of doing something else and just check the tightness of them. Copper creeps slightly when first screwed down and a second torquing is a good idea.
Great video! I have a large property which will be a 6bed HMO I want Every room to have it’s own CU so I can sub-meter that.. Is correct to have a Henley block 1 to 6 and have a 16mm wire running to each room? Thank you
What you are suggesting is achievable. The cable sizes will depend on the loading for each unit. How many amps to each unit, what size Cu in each unit, what circuits in each unit,what diversity is applied etc. Thanks for watching. Dave.
thanks for your great videos..but i have seen many places they get fed from main CU on 32A mcb ,running 10 or 6 mm SWA and RCD protected on 2nd cu. is it anything wrong if to do that way then ?
If the cable sizes are correctly chosen then that is good too. The beginning of our video says that we are assuming that there are no spare ways in the CU to do what you suggest, so we give the solution.
How would you incorporate selectivity into the scenario mahdi has said. Should a delayed type rcd be used somewhere in the sub board or along the circuit to stop the main consumer unit from tripping?
@learnelectrics
Yes, a delay type RCD upstream is an excellent idea where there are two or more RCDs downstream. Have a look at Regulation 536 in the Wiring Regs, especially 536.4.1.4 Good points. dave.
Amazing 👋🏻
Thank you for your short but very powerful compliment. Much appreciated. Dave.
Hi can you please explain or do a video on filling out certificate for a remote 2nd board thats been converted to a tt system. Thanks
You will find the video on the link below very useful when completing certs for any second or third board, and indeed the first board too. Thanks for asking, thanks for watching. Dave. Filling in certificates for second boards kzhead.info/sun/mK2GYJGtjaaMY30/bejne.html TT systems Zs and Ze kzhead.info/sun/e7evmbplf5uCiac/bejne.html
Would this application work for a EV charger with a upgraded 100A fuse on the main consumer unit? The main consumer unit has no spare or surge protector, the House has solar & batteries.thabks
I would suggest getting the Code of Practice for Electric Vehicle Charging Equipment Installation, published by The IET and available from Amazon. There are lots of things to consider for EV charging. Dave.
Would you say db2 earth can be run out of db1 or split with a block before both? Thanks
If extending fro DB1 then yes. The Line, neutral and earth should all come from the same supply point.
Thanks your videos are the best on hers
What type of cable is recommend to supply second consumer unit? 16mm SWA or can we run 16mm T&E from henley block to second consumer unit?
If it was me it would be 16mm double insulated meter tails if internal, or SWA if the cable was going outside.
How do you do this for a 3 phase? Do you use 4 Henley blocks instead of 2
Basically yes. One for each phase plus neutral. Don't forget earth. Thanks for watching and lots more to come. Dave.
Hi What size cable should be used for this secondary consumer unit
Whatever size will take the max expected current and taking into account environmental factors, volts drop, distance etc. There is no set size. Dave.
My head main is split. The live goes into the cut-out fuse and the neutral goes into a sealed Henley block. Then both the L & N go into the meter. Is this normal? Great videos btw!
If its as the DNO installed it and it is still sealed, that should be ok. There are a thousand and one different examples of head wiring. Thanks for watching. Dave.
would it be possible to do a video how to wire a kitchen in domestic setting or how to wire a house?
Have a look at this video on ring and radial circuits. kzhead.info/sun/aauHkpWLineghJ8/bejne.html And don't forget about the search function on our dot.com website. Type in your question and it will bring up more help videos. Good luck. Dave.
Hello, I've had an electrician remove an MCB circuit and use that to run an armoured cable out to another consumer unit in my out building, till then I was running all the lights etc from an extension lead, since he's done this my original house consumer unit it's tripping an RCD, he's blaming my wiring in my outbuilding, but it can't be as I was using an extension lead before. Do you think this is how he's wired in the outbuilding consumer unit into my house consumer unit? Thanks.
Without actually seeing the install its difficult to say. This sometimes happens when circuits are changed or upgraded. You or the electrician need to investigate. Is it when any light is turned on, is it when all the lights are on. You will need to establish a pattern to it tripping. Sometimes, the extension lead will give just enough resistance to not cause RCD tripping if there is a fault, especially long extensions. Is the new wiring damp, sealed connections etc. Most electricians will come back and help you to solve it.
Update for you, the guy had wired the Neutral to the other RCD block (Which was still bridged in) however, by putting it on the correct side everything now works.. Low and behold he's trying to blame me... As expected.
Could there be an argument for installing 2 x isolators, one for each board? Thanks for the great vids by the way...
Absolutely there could James. In fact I do that if I am installing a second board in an outbuilding or garage that is not joined ion to the house. Any problem with the external wiring, it can be isolated and made safe. Good question. Thanks. Dave.
@@learnelectrics4402 have you done or are you doing a video on when you would and when you would not add a second board for things like garages or outbuildings? Or where would I look in the regs?
James, adding CU's is between you and your customer. Nothing in the Regs. Hope this helps.
@@learnelectrics4402 can it have anything to do with volt drop? Or I guess just practicality? Sorry for all the questions, just keen to learn..
Two different things James. Do you want extra circuits that is the question you need to ask. Any circuit existing or added should meet volts drop rules. See our video Voltage Drop Calculations on this link. kzhead.info/sun/jZGkp5pwZ4V_oqc/bejne.html
Why do I have a 2nd 1P consumer unit sourced from an MCB in a 3P supplying consumer unit?
I don't know the actual setup you have Rami. There could be lots of reasons. Usually distributing single phase to specific areas. Dave.
Would you need to put an 80amp isolator supplying the other consumer unit…
I used to do that if I was installing even a 40A second CU in a garage our outbuilding. It means that you have a method of isolating the supply to the garage when not needed. There are recorded cases of neighbours plugging into a garage supply and the customer being unaware of it for years.
@@learnelectrics4402 so u can just Henley block straight into the other CU without an isolator if it’s same building
can u take the supply from the main switch to feed the second CU
You may not get two meter tails into one hole on the main switch. From what you have said, it sounds like the second CU is only a small load. Rather than the main switch, put a 40amp breaker in the board to feed the new CU, if the original will take the extra load. Don't forget safe isolation when working around consumer units.
@@learnelectrics4402 thank you soo much this cleared alot up for me I will be visiting this channel alot more and ask plenty more questions aha thank you again. what cable should I use to feed the new CU would 6mm² Swa be ok?
Have a look at this video if you are taking a feed from an MCB. kzhead.info/sun/idiNhc-Np4NjhZs/bejne.html Hope it helps.
why do we need a switch after the meter? cant we just pull the fuse from the main supply box that goess to the meter each time we want to isolate??
That's one solution but only isolates the line conductor. Adding an isolator will isolate line and neutral.
@@learnelectrics4402 interesting .. wot are the dangers of touching a live neutral line on the incoming supply feed?
Hi guys, if I was to add a sub main for a new consumer unit in a new Anex, and I was running 10mm swa, does the consumer unit main switch have to be higher rating that the sub main main switch?
No. If it is a switch only, then as long as the switch is at least the correct size for the part of the circuit it protects it is ok.
@@learnelectrics4402 hi sorry if I’m getting confused here, Protective device is equal or less than current carrying capacity of cable , bs7671 says 10mm 3 core ref method D is 50A so will that need a 50A fuse or less at the switch/fuse at main incomer? 😃
Paul, two different things. A main switch (switch only) should be able to disconnect at least the maximum current of the circuit. Most houses are protected by a 100A incomer fuse. If you know the loading may be close to 100 amps at times, then a 100A main switch is ok. A fuse or breaker should disconnect before the maximum rating of the cable. If you know the cable rating is 14 amps say then a 10 amp circuit breaker is the choice, not a 16 amp one. Always protect the cable.
@@learnelectrics4402 got it thanks! :)
That's great Paul Also, if you look on page 188 of the Wiring Regs, there is a table that lists the functions of different devices, whether they are switches only, overload protection etc. main switches are usually BSEN 60947-3 types
thanks again, where the consumer installation start, consumer's tail?
From the consumer end of the incoming supply tails. Thanks for watching.
Nice one dave another interesting one 👍 just of topic but which is the best way to find the correct college course and price to be able to retrain as an electrician to the stage where you can register with a scheme napit niceic etc and am I right it usually takes 3-4 years to complete .ill probably get stick in the comments I understand I would never be a proper time served spark but I’m just thinking of an option as I find electrics very interesting to the point I’ve nearly completed all the sparky videos on KZhead 😂 including your videos dave 😂👍👍
Don't ever think that you cannot do it. Lots of people are in the same situation, later in life etc. If you want to be a sparky you can be. 3 to 4 years not true unless you take the apprentice route or only approach this part time. A lot comes down to your determination and time input. To join a scheme like Napit or NICEIC etc. you will need to show educational achievement (exams) and practical skills (assessments, on the job etc.). Plus, the more you practice and read the better you will be. Make your own test board and wire it up and test it. Test your house, change switches or ceiling roses in your house. These are all skill building and good for the confidence. And actually go to at least two different training centres and put your story before them. Don't rely on the phone, turn up on their doorstep and ask to look at their training facilities. See what they suggest, the routes, the time etc. If they are going to take 3 or thousand pounds off you, the least you can expect is a fair chunk of their time and attention, not just 5 minutes, before you make a decision. There is no "Instant Electrician course" so be aware that some will try to sell you one and three week courses that guarantee you are fully trained (not). It takes time. Months in fact. The most important thing is being able to apply your theory to practical work. And testing skills are very very essential. Do not part with ANY money until you are certain that you have found the right centre. Speak to NAPIT for instance, their training packages are very good (I used to teach for them). They might be a little more expensive but they will give you good training. So will other centres too. Just watch out for the one's that promise that you will be an expert after 4 weeks. And I will say it again, read and practice over and over again. That's why professional snooker players are so good. They practice with the same balls on the same table in the same room for hour after hour after hour. And then they do it all again the next day, and the next, and the next. Good question. You can do it and don't worry about where you started, it's where you finish that matters. Dave.
@@learnelectrics4402 nice one dave thank you 👍👍
You are very welcome buddy. Keep me in the loop and thanks for your support with the LearnElectrics channel. Dave.
@@learnelectrics4402 I will do dave 👍 thank you again, can’t wait for more videos 🙌🏻🙌🏻 cheers
Thursday this week is garage door motors and next Monday is 2 plate lighting circuits.
L u bro
Thanks, glad you liked the videos.
Hi, Is it OK to have 2 Main Switches in the same consumer unit , one for the House and the other to isolate a garage consumer unit which is fed from the House?
Why not use an RCCB. This will act as a 2 pole disconnector and RCD protect the cables to the garage.
Can two consumer units be installed in series?
Have a look at this video, I think this will answer your question. Thanks for watching. Dave. kzhead.info/sun/jK2lhMatepqIhpE/bejne.html