EARTHING a SHED or OUTBUILDING - TT - TNS - TNCS
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- Опубліковано 12 лют 2022
- With more people working from home now, here at LearnElectrics, we have been asked many times about converting a shed into a work space or work cave as some call it.
The electrical supply to such a work space, shed or outbuilding will need careful consideration as will the earthing arrangements.
It is not just a case of hammering an earth rod into the ground and installing any old cable.
In this video, we will show you some common scenarios and solutions to help ensure a functioning and safe installation.
This video is No.120 on our UA-cam channel where we have videos on a wide range of electrical topics.
To see a full list of all our LearnElectrics videos, click on the link below.
/ @learnelectrics4402
You can also view all our videos by typing LearnElectrics all one word into the UA-cam search bar.
Always work safely, electricity can be dangerous. If you are unsure, stop and seek advice.
This video is provided for guidance only. Every electrical situation is different, please check and ensure that you are applying this learning information to your own individual circumstances correctly and safely. If in doubt, stop and seek competent advice.
After watching some videos, I became so interested that I watched all the videos available and my knowledge increased a lot. Without any doubt this is the number one UA-cam channel for learning about domestic electrical circuits. Best wishes!
Super feedback Sajad, so glad it is helpful. It makes all the effort worthwhile, thanks for your support. Dave.
The best most well explained videos anywhere, thank you
Good of you to say, thank you. Dave.
Clear & precise, all video's should be this way, now I understand what the Electrician was explaining to me.
Thanks, glad it helped.
Sir, you’re amazing. Explanation is clear, thorough, and reconciles what my current understanding.
Appreciate your videos!
Thanks for the great feedback. Glad you found them useful and thanks for watching. Dave.
Thanks for the wonderful video, earthing and surge protection is one of the very important topics which is usually neglected.
Thank you Mangani, your comments are appreciated. Dave.
I watched this video before I did outbuilding connections for better understanding. Thanks David
Great to know, thanks for the positive feedback and thanks for watching. Dave.
Very good David..very informative..keep up with the good work!
Thanks, will do and thank you for watching. Dave.
You should be employed to rewrite the regs documents. You make it so easy to understand and remember.
Now that would be good. Thanks. Dave.
I always learn something from your videos. Thanks
Glad to hear it. lots more to come.
Dave, really love ur videos, contents covering various areas, thank you very much
Glad you like them and thanks for watching, appreciated.
Cracking vid, very informative and dumbed down too!
Thank you very much. Thanks for watching. Dave.
Very well explained. Thanks for such an easy to understand video. Far better than some of the connections magazines articles which don’t explain the reason to convert TN into TT. Highly recommended watch for all electrcians.
Thanks for watching and for the great feedback. Dave.
Thank you for an excellent explanation🙏
You are welcome, thanks for watching. Dave.
Love the clarity of your videos. I wish UA-cam content like your's had been available when I was an apprentice, learning would have been much easier.
Unfortunately the Internet wasn't available back in the olden days.
Today's apprentices don't know how lucky they are.
Well done, and thank for your efforts.
Thank you. I agree, there is so much help available today. I remember sitting in Waterstones reading electrical books because I couldn't afford to buy them.
Thanks for watching.
Dave.
We're are also 'lucky' to have the police.....
Another superb video 👌👍
Many thanks Martin, thanks for your support. Dave.
Really interesting. Thank you.
Thanks for watching and supporting the channel. Dave.
Nice one 🙌🏻🙌🏻 thank you 👍👍
No problem 👍. Thanks for watching and for your support. Dave.
Thanks for sharing this
My pleasure David and thanks for the support.
Thank you.
You're welcome Kip, thank you for watching. Dave
Hi. Many thanks for your easy understandable videos. You are doing excellent. What I want to recommend is that. Could you please can you show some examples on the site. İt will be more clear.
Thanks for the comments and the support. Much appreciated. Dave.
Good to know . I have a project starting in July , temporary install 3 x 20Ft Stores , 1 x30ft stores and toilets which will have pipes going in to it but not sure if will metal or plastic pipes
Good luck with that, a nice little project. thanks for watching. Dave.
Great video - but would also be good to explain the more common requirement of safety providing a couple of SOs and a light in a shed via a fused spur from an existing ring main in the house and possible pitfalls, dos and don’ts etc.
Excellent idea Bagpuss. That could make another video. Thanks for watching. Dave.
If it doesn't have water supply or extraneous conductive parts you should be ok.
@@g-labs No, mine doesn’t and there is a 3A fuse in the FCU so effective fault discrimination with the protection on the upstream ring circuit should be ensured 👍
Great initial comment about TT being two earths, one at the property, and one at the (generator) supply [or substation]. I'd not cottoned on to that perspective of how that "TT" terminology came about.
I'd always translated it in my head as "Transformer-Transformer", or the two terminals at the local pole mounted transformer, or equivalent.
In some ways I should have realised - FiL (sadly passed away just under a year ago) had great stories from WWII and thereafter of not being allowed to connect to the "Board's" supply earth (lead sheaths everywhere), and other now no longer acceptable practices (slapping the end of a cable to see how long the spark was to determine voltage, wiped lead solder joints, banning of single core ring mains, etc.)
Excellent diagram of the carried earth fault from elsewhere to a 'poorly' bonded system.
The problem of diverted neutrals (current in earth bonds) could have also been noted (see that gas meter that burnt out because of such diverted currents!)
Thanks for the great input Philip, really appreciated. Dave.
Regarding transporting the earth on a TNCS system… it’s a matter of the weighing up the dangers. On one hand you can have the broken PEN at the house, thereby placing a voltage on the earth conductor, or the induced voltage from neighbouring services due to a fault.
Thanks for watching, lots more to come. Dave.
This the most interesting topic that i was looking for since we build our outbuilding at the back. The only thing I am disagree on this is when you said we put TT system on shed and on this if there is running trough water pipe and we induced voltage from the next door when the replaced they pipe with a plastic. and to have this scenario you have to take consideration of the ciruit its need to be parallel and have sufficient of energy to induced any voltages to adjacent circuit that may have be affected. And Induced Voltage mostly common on High Voltage system and this a natural phenomena. It may appear to any Pilots cable using 30V DC. But this have to be running parallel with HV cable normally 11kV upto 132kV. Or any 2 parallel HV transmission lines. But for me I haven't encounter situation like this on the LV. If you encouter this during your time please do let me know.
Thanks for the input Alan, interesting, and thanks for watching. Dave.
Based on the illustration in this video, it seems that in Uk in a tnc-s system you do not provide an earth electrode inside the house. This electrode would be great in some scenarios like a broken PEN.
This is the way its done in the UK Sajad. We can only comment on UK Regulations even though most electrical practices are similar around the world. Thanks for watching. Dave.
I've just been to a job where they have a 3 core, 4mm swa to a shed in the garden. The shed is metal and the installer has exported the tncs earth into it 😏. Also, there was an EICR carried out a couple of years ago, which didn't pick this up!
I sometimes wonder about the time spent on inspections. The quality of inspection varies dramatically.
can you explain what you mean by exported the tncs earth into the shed please.
in my 3rd year of training and always learning =]]
if im thinking right you mean the shed needs bonding but to comply it would need a 10mm earth? thus 4mm is wrong ?
cheers
Hi Thanks for the videos you do on UA-cam. I've finished watching the one "EARTHING a SHED or OUTBUILDING" .
My question to your video is... We have a TNCS at the house and would like to connect 3 separate outbuildings, daisy chained?(1 is Brick, with a WC, the other 2 are normal wooden sheds)
We have not long had the garden landscaped and had a 16mm 3-core saw layed. is it possible to use this one SWA cable to feed all 3 outbuildings.
A concern i have is that the electrican i had advise me originally said i would need an earth rod for each shed, or for atleast the brick one (with the WC)... having now watched your video and my house being TNCS and having 16mm SWA i feel confused as to whether this is necessary?
Any help on this would be greatly received
If it is 16mm 3 core SWA there shouldn't be a problem. The 16mm earth is above 10mm for bonding. And the WC is not a special location unless it has a bath or shower in it. Keep it all as a three wire system. Just check your load requirements and voltage drop for the cable. Thanks for watching. Lots more on the channel and on the website. Dave.
I drilled a hole through the wall from the back of an indoor socket, installed a weatherproof 13A fused spur, ran 2.5mm 3 core armoured cable to my steel garage (10 meters) and into a weatherproof socket inside the garage, then from there a spur goes off to 5 sockets and another spur to power a 12v psu for my diesel heater and a couple of led lights. Everything is earthed from the indoor socket, armoured cabled is earthed, sockets etc all are aswel. Do I need to add a extra earth on the steel shed?
I only use the shed for my vinyl cutter, computer, printer, heat press etc, if I had everything on at the same time then the amps will still be below 13amp.
You will need to bond the steel shed, certainly. Dave.
Great
Thank you for watching.
I have this current scenario and currently just use an dedicated 16a extension 3 metre cable plugged into an outside socket into a 16A C form input into the side of the shed when I need power to strip lights only but now I need a dedicated 13amp socket for power tools. For safety I need to split the lights into one circuit and the power into a separate circuit . I was thinking of fitting one of those garage Chint consumer boards in the shed ( Screwfix) but I don't know if this would cause false tripping from the main Consumer board
The extension cable would be disconnected and removed after use and stored in the shed as required so not a permanent fix
Take a look at this video and thanks for watching.
EXTENDING CONSUMER UNITS, click on the link below
ua-cam.com/video/pdKtFEhP3Eo/v-deo.html
Can I advise you to seek the advice of a qualified electrician. An extension cable is not adequate and for a garage consumer unit, the installation needs verifying for cable size, voltage drop so the protective device works correctly and testing. It's not a DIY task in any stretch of the imagination.
Unless i have misread the latest regs I have read that you should not use the earth in the swa cable on the systems as you are porting the earth from the incoming mains and they can have a different potential which can be dangerous
If there are no extraneous parts and the armouring is correctly terminated it is permitted, Thanks for watching. Dave.
Great video, there are others on YT saying you must use an earth rod in case there is a PEN fault ??
Some DNOs will insist, others will not. A lot depends on your supplier.
We've just moved into a 1920s bungalow with a detached garage (35m away). The earthing system to the house is TT.
There is a 10mm 3 core SWA cable that runs from the consumer unit to the garage where it feeds 3 lights and 2 double sockets. There is a tap in the garage that is fed directly off the main water supply which was rellaced a couple of years ago with blue mdpe plastic pipe.
This tap is not earth bonded, and it looks like the SWA cable is used to provide the earth.
Everything seems fine, but is it legal?
If the tap is at the end of the plastic and there is no other metallic connection from the tap then that is ok. It looks like the supply to the garage is treating the garage as any other room in your bungalow. I assume you are 30mA RCD protected which is the main requirement for TT systems. Thanks for asking. Dave.
@@learnelectrics4402 Thanks - put my mind at rest.
Very informative, thank you. Should the neutral and the earthing conductors be linked in a TT installation, as they are in the case of a TN-C-S arrangement? I believe there shouldn't be a metallic connection between earth and neutral in a TT installation, but I'm still learning, so I could be wrong.
Thank you for sharing your knowledge with us.
No, don't link the earth and neutral yourself, you will lose the RCD protection. Hope this helps. Dave.
@@learnelectrics4402 Are you sure about that / can you explain why?
Just run the water supply to the shed in plastic pipe. It's easy enough to do that outside the shed, maybe with an access point to the joint. Whilst it makes sense to put 10 mm^2 SWA into a new installation, for some like me, who has a 4 mm^2 SWA underground cable to a detached garage, it would be easier than replacing an underground cable should I ever want to run a water supply to it. However, I guess a retrofit of a water supply to a garage is a job for a plumber, who might not know about this added complication.
Good comments, thanks for the input.
So if I have no extraneous conductive parts in the outbuilding, I am ok to take the incoming TT earth at the house and extend this to the outbuilding via 3core SWA?
Or should I use 2 core SWA and only earth the house end of the SWA armouring, before installing a separate earth rod at the outbuilding?
Hi, many thanks for the brilliant video. I am however wondering about a hypothetical problem. If for whatever reason I drive two rods into the ground say 30 metres apart and almost connect the two together, say a steel fence that ends near the second ground rod for instance. Am I in danger of being electrocuted??
Generally we are assuming the ground and any rods as being close to zero volts. Properly chosen RCDs and MCBs will limit any duration of shock to a lot less than a second. The quicker the system disconnects the supply, the more chance you have of surviving an electric shock. Hope this helps.
Great explanation.
One question, someone before be has installed 2 core SWA and an earth rod. We have a TN-S system in the house. Is the only way to improve safety on this to dig the cable up and start again?
A lot depends on how they have placed the earth rod, is there an earth rod at both ends, have they made it a TT system and taken suitable steps in the shed with the shed CU. Have you considered running suitably protected Earth conductor immediately next to the buried SWA, is the steel wiring of the SWA properly connected at both ends so that it is performing an earth function. This video may help.
ua-cam.com/video/qAah0Uqx9oI/v-deo.html
Thanks for the direct reply @@learnelectrics4402 . I do not see an earth rod at the incoming cable or anywhere around it, only one outside the garage. The steel sheath is not connected to the earth bar at the main consumer unit. I would have to check the garage sub panel but I don't think it is there either. But based on what you say in this video, I don't think it would have enough capacity anyway as its running on a 60amp breaker at the consumer unit. Digging a new cable is a big pain because of the path, so trying to determine if I definitely need that before I do! I note that you say TN-S systems usually have soldered on earths, where as mine is a clamp, but I assume that makes no material difference?
Good Video, But SSE where I am won’t allow you to export your PME supply to any outbuildings. Always have to TT 🤙🏼
Interesting, even as three wire. Thanks for the info and thanks for watching. Dave.
@@learnelectrics4402 Some nonsense about fault conditions if a PEN conductor is damaged.
Keep up the good work on the vids
I have a scenario that many radio hobbyists also have, my house is TN-CS. A mains powered radio is connected to a ground mounted antenna in the garden. So the outer of the coaxial cable is effectively linking the house safety earth to the ground. Obviously in the event of the incoming mains cable losing the entire sheath connection I could have a scenario where the earth wire of the ring main and the outer of the coax could carry significant fault current which might exceed their current carrying ability. I can think of ways to avoid this happening, however is there a standard approach other than ignoring the possibility? Proper radio sites do use comprehensive bonding systems, but the likes of minicab offices don't.
I would consider using a radio-frequency isolating transformer separating the earthed radio from the outer of the co-ax. Obviously this transformer would need to be rated to withstand 240V between primary and secondary under fault conditions.
@@davidfaraday7963, an interesting solution, though quite tricky to implement over a wide frequency range.
@@g0fvt The technique is widely used in audio to address problems with ground noise. A properly designed RF transformer should be able to cover at least as wide a frequency range as an individual aerial array
David has you covered with the answers below. Isolation transformers will separate the earthing. You would be best advised to contact a radio specialist for the right equipment for this. It may be a common request and they may have off the shelf solutions. Thanks for watching and thanks for the question. Dave.
Thanks David, I agree with your suggested solutions. Thanks for the support. Dave.
The earth connection on a TN-S system to the lead service cable is not soldered, a special clamp is used although self tightening springs are now the preferred method. Either way the DNO is responsible for both TN-S and TN-C-S earthing arrangements.
Absolutely Steve, the DNO should be called for any main earth problems on their side.
Interesting I thought an out building had to be on a TT system the same as a caravan park in BS7671 but you are saying I can use a tnc-s system and that is ok with a 30 am RCD for Additional protection
You can use a TNS system. The TNCS will stop at the house and become a three wire system, effectively TNS. We don't recombine the earth and neutral, they stay separate. Hope this helps. Dave.
We upgraded our house fuse box last year and the electrician fitted appropriate earth bonding to gas and water pipes in the main house. He didn't carry out any bonding work to the garden sheds which are connected electrically from the house via a plastic piping running along the garden border and feeding into a separate shed fuse box which serves several power sockets for power tools ,garden mower etc , the sheds are all wood and it looks like the wiring is black,red,copper strand in a thick white sheath, the sheds have been like this since 1990's when my father installed it so does it need any further bonding do you think?
If there are no extraneous metallic pipes in the sheds, water, gas that go into the ground then not needed. I like the idea of the wiring in plastic pipe if its above ground, protects it from strimmers and mowers. Dave.
@@learnelectrics4402 Dave Thanks for that. No there are no metallic pipes in the sheds, we have disconnected a sink unit and water heater that my late father fitted to one of the sheds as he was into photography and enjoyed developing his films, as to the plastic pipe that serves as a conduit for the wiring from the house we plan to bury this completely in a trench as the plastic pipe is showing signs of becoming brittle so to be on the safe side that is a little project to get going soon. Peter
Excellent, I'm currently planning a large ish (6.5m x 4m) garden room / office. Yet to run my electrical plans past an electrician, but I'm hoping to take the supply straight from the meter cupboard - so henly block > switch fuse > SWA > Office CU. Is that a common method? Would make a good video!
@P A This type of installation is notifiable, a qualified electrician will need to be involved; but that doesn't mean I don't have a say in the design and quality of the install. If that offends you.....tough.
Gary, take a look at this video
EXTENDING CONSUMER UNITS, click on the link below
ua-cam.com/video/pdKtFEhP3Eo/v-deo.html
You're approaching it the right way. Dave.
Not sure if this was for me Gary. Has someone said something that I've missed? That's not what this channel is about. Let me know. Dave.
@LEARN ELECTRICS Not for you Dave. Looks like the comment I replied to has since been removed.
@LEARN ELECTRICS Thank you Dave. I will be getting a qualified electrician in, but like to be involved.
Excellent video once again. The db in the house, you would use an (40 amp rcbo) for example. At the shed db what device is necessary, im thinking 2 rcbo’s in same circuit as such would cause nuisance tripping?.
MCB in the house, rcd protection in the shed if there’s a board in there.
If yours a spurred socket and light, rcbo in the house board
@@newlinerealboi3434 doesnt the cable need rcbo protection from house to shed?
@@Dibbo1979 it wouldn’t if the cable feeding the shed is a SWA ask the risk of someone damaging the cable would be low
I didn't think you could export the earth on a tncs system.in case of a pen fault ?
You can't export it as a combined N+E. It goes as a 3 wire system. Dave.
Whats you option on the earthing for outside electric gates and garden sockets away from the house
Many people with install an earth rod in the vicinity. Thanks for watching.
With a TN-C-S should a neutral fault occur effectively the earth will in turn carry the load increasing the chance of shock through any earthed connection. Would that not make the best option a TT so it has a guaranteed earth and probably RCBO on the individual circuits? Also what’s you’d thought on the incomer if a TT is better should it have RCD protection or would the RCBO on outgoing circuits negate the need.
If the RCDs/RCBOs and MCBs are right, the supply should disconnect within 0.4 seconds or less. A lot less with RCD devices. Some have an RCD device at both ends. Usually, the one nearest the fault goes first.
Dave.
My shed uses solar power only, the energy from the 500 watt solar array is stored in 2x 200W batteries, easy to do and the system is adequate for lighting, small power tool use, and charging tool batteries. Not suitable for electrical heating though....
According to UA-cam guru John Ward, this is classed as a 'TI' earthed system.
Great feedback and interesting. Thanks for watching. Dave.
Better sound this time with NO overloading (clipping)
Thanks Les. Thanks for the support.
If the SWA was on show due to danage and the neighbours water supply was energized by a fault. Would the Swa pick up a live feed and energize the earthing arrangements in the house and shed? I know its a odd question but.?
If it was close enough to pick up induced voltages yes. It will act like an earth rod.
Good question. Dave.
@@learnelectrics4402 I thought that was the case i know that was thinking out of the box but it makes me wonder how one could future proof this problem that would probably never happen. The only way i can see this is not to earth the SWA at any end but thats not the correct way either bit of a conundrum wouldn't you say. But thanks for your reply.
How about...cut in a plastic fitting above ground or shed entry point on the water supply pipe
thanks for watching, appreciated.
Why not label LIVE with VIVERE =V?
I remember a Mars vehicle crashing onto the planet because they used different standards of measurements.
Archaic standards like feet and inches; pounds and ounces, Fahrenheit should be pitched into museums.
Electricity is dangerous enough without bringing confusing terms into the jargon.
Great video, thank you.
Good one Colin. There are so many confusing words and then they change them.
Maybe its a test to see who's paying attention. And yes, I remember reading about this incident. Different standards on different parts of the design.
Thanks. Dave.
Please be aware that PME/TNCS is not all it's cracked up to be as if there is a loose neutral at the transformer then the earthing arrangements can become live. Also it worth mentioning, that the new 18th Adition Metal Clad boards, bring another risk to 'exporting PME' and not recommended for DIY'ers..
Absolutely right Jonny. Thanks for your input and thanks for watching. Appreciated. Dave.
You would think a pipe underground would be well earthed and have no voltage ? Does it depend on soil conditions ?
Electrics can be full of surprises. Yes, soil resistivity can be a big factor, hot and dry in the summer make the readings high and wet in the winter makes them low. Thanks for watching, lots more to come. Dave
It always strikes me as inherently risky to export the earth on a system which is not assured to be TNS as a fault in the combined N/E conductor could result in high voltage appearing on the main house earth. Local TT earth would seem to me more appropriate as that would ensure the intention of minimising the risk of any dangerous relative voltages such as between shed & earth proper such as if someone took a laptop outside to work whilst on charge. Considering a shed as one would a car charger seems a good idea to me?
Interesting comments Alan. Thanks for watching. Dave.
A “ high” voltage could not occur on the house M. E. T . as domestic electric services are in the low voltage range (230v)
@@steveclemons8373 I should say 'dangerous ' I guess so as not to confuse with network voltage definitions...
Unless TT or TN- S , I'd install a " rod " isolated at the shed from the incoming supply to the shed
Hi. Have a shed/man cave to re-connect (it’s temporary connected to kitchen ring with 5 meters of swa 2.5mm). There is 2.5 twin and earth sticking on the wall to connect it to (10meter run from consumer unit to the outside of house). Shed has double socket and 4 down lights. What’s better: A. Connect it to spare 16A mcb RCD protected and fit 16A and 6A mcb’s in the shed. Or B. Connect in CU to 16A mcb not rcd protected and in the shed fit RCD and 16A + 6A mcb’s ?
I would use an RCD in the house consumer unit as this protects any damage to the cables. Dave.
@@learnelectrics4402 Thanks for being back with me. Same what I was thinking. Only thing what I was considering with connecting to separate 16a MCB in CU and fitting RCD in shed was that if any earth fault in shed then will trip only the shed not all mcb's connected to the same RCD in CU. Maybe the best would be to replace that spare 16a MCB with RCBO in CU and then 16A,6A in the shed.
Hello dave i have one quastion is why almoste using earthing systeme of TN and TNC TNS in industry installation why not use TT . Thinks
TT systems were the original systems a hundred years ago, then updated to TNS, then TNCS. It's just the age of the installation. Properly installed and maintained, they are all safe. You will still get TT systems installed today in some locations. Good question, Dave.
@@learnelectrics4402 thinks dave for this information but can use RCCB in system TN CS is there no probleme . Excues me because i trouble you with my quetion.
was thinking that a 10 mm cable is a fairly good size. (whole cable or one conductor?) Just how much power is going to this shed? Here in the USA that wire size will be a work shop with a welder or even the ability to fast charge TWO electric cars at the same time.
Thanks Rupe. For the example here with a need for bonding in the shed, 10mm for each conductor, you need to provide a 10mm conductor back to the house for the bonding and 10mm SWA will do this. All done in one job then. Thanks for watching and thanks for the feedback. Dave.
@@learnelectrics4402 ... this is were I get confused. Your 10 mm wire size is just over 0.39 inches, which converts to 2/0 wire gauge, which in copper can carry 175 amps at 240 volts. (numbers we use in the USA) That's why I was wondering what is being powered in that shed. BTW, I presume your wire size is the actual conductor diameter. In the states we'd use a #6 wire for the earth connection. That works out to just over 5 mm.
@@rupe53 10mm is not the diameter, it's 10mm2 which is the CSA (Cross sectional area) and is the same as your 8 gauge AWG
On the TT system, why not run a 3 core cable to the shed and use the house earth?
You can, but often you will want to bond the area around the shed to the same potential as the house.
Thanks. So, perhaps a second earth rod and bond any extraneous parts? Especially if metal construction?
Sir. According to you , which earthing system is best and why ? . In India which earthing system is commonly used.?
We have all three types in UK. In order of age this is TT is the oldest, then TN-S and the more modern TN-C-S
As an electrician I just work with whichever system is on site. Thanks for watching, lots more to come.
With tncs your not exporting tncs because its now a 3 wire system after the supply . Is that correct dave
Spot on. Once we split it at the incomer, we never recombine it. Thanks for the input and thanks for watching. Dave.
This is annoying Dave! BS7671 goes out of its way to over complicate the non export of a TNCS supply where what you really mean is PEN conductor ! You lot make everything harder than it needs to be!@@learnelectrics4402
My boss has told me that you are not allowed to export a TN-CS earth to an out building, you must install an earth rod at the out building? Is this true?
Absolutely right. The TNCS ends at the house and becomes TNS effectively. Have a look at the incomer for TNCS on the little house in the video, you will see where it is split off into separate Neutral and Earth and is not recombined. Everything from the house is three wire or two wire plus sheath (which is three wire). Yes, your boss is correct. Dave.
No this is not true . The NIC ,Napit etc say it is prohibited but BS7671 does not prohibit it .
@@learnelectrics4402 Can you state the regulation that prohibits using the pme earthing in an out building . What is wrong with using a 10mm for any bonding ?
Just started listening. On a headphone set the sound is only in my left ear. Is it just me ?
Interesting and thanks for the info. I used a different microphone last week. Will check it out. Dave.
I'll check this out. Thanks. Dave.
I see you keep saying you are not exporting the TNCS arrangement to the outbuilding, as yo are using 3 core or the armour. This I believe to be irrelevant, you are still running the risk of the installation including the shed becoming live if the pen conductor is broken. Therefore the shed must be bonded to make sure there are no differences in potential between the house and the outbuilding. I have been told by 3 tutors that the regulations require the shed to be a TT system incase of a broken PEN conductor. As I understand from reading the regs myself, it either has to have an bonding conductor from the MET to the outbuilding that matches the size of the house bonding or bigger to account for volt drop ove the distance. Or a TT system should be installed as the regulations require the earthing arrangements to be separate from the main dwelling. Any thoughts
I was pulled up on an NICEIC assessment for exporting the TNC-S to a separate outbuilding that was converted. Got me to TT it.
Thanks for the comments. Once the TNCS is separated in the house it should stay as a three wire to the sheds. We shouldn't be exporting TNCS back out again. The drawings show it as three wire. Hope this helps. Dave.
What is the purpose of the main earth?
To provide a low resistance path for fault currents.
What about a shed brick shed 10m from the house.
Fed from a FCU?
The Shed is actually like 3 metres from the house but its not possible to go under so I'm going along the brick wall of the house and brick wall along the side so need 10m
Treat it the same as any other outbuilding/garage that is remote from the house/CU.
Have a look at this video on our YT channel and thanks for watching. Dave.
ua-cam.com/video/YIlTbuChRSY/v-deo.html
@LEARN ELECTRICS unfortunately my board has no spares.
And there is no room to fit Henly boxes.
I have had an electrican out and that's what he told me.
He said I don't need a Garage CU for a couple of sockets and a light.
Can you elaborate on the dangers of an earthing rod being close to supplies? Why is an outbuilding any different to the main house? The earthing rod in the main house (assuming there is one) will almost certainly be close to the supplies, since the supplies go to the house.
I don't see how you get a shock in the scenario you described, since you are touching two things at different potentials. You say the earth would be energised to 150V, but what is that relative to? Surely, potential is irrelevant, only potential difference matters?
Exactly. the soil can have different potential during faults, that reduces as you move away from the fault. It depends where you are stood and what you are touching. I may do a video on this, its now on the list.
@@learnelectrics4402 Thanks. Isn't that only an issue if the earthing rod is not located close to the outbuilding? As long as the ground the earth rod is in and the ground you are standing on are essentially the same ground, there can't be a significant potential difference, right? If it is a large outbuilding such that an earthing rod on one side of it could be at a significantly different potential to the ground on the other side of the building, couldn't you fix that by just putting a second earthing rod on the other side of the building and bond them? Any fault current would then flow through that bonding rather than through you and the outbuilding would be kept at a near-constant potential. (Any extraneous conductors in the outbuilding might provide that for you already.)
Been watching some American bonding videos they sometimes use this method of bonding 2 rods between ground points. I think I’ve asked this question to NICEIC before and they’ve indicated every earthing point needs to be suitable for the highest level of fault current on every ground bonding for that installation.@@thomasdalton1508
If a out building is 10m or more away from the property and the DNO supply is TNS-C then an earth electrode must be provided. Exporting the earth is not good practice.
Thanks for your input Paul. Thanks for watching.
I would argue that a metal waste paper been sat on the ground would be grounded,
Thanks for watching, thanks for the input. Dave.
Increase your audio output, I am slightly deaf but not that bad, I have every possible volume at max and I'm still struggling to hear you. Thanks As much as I managed to make out and my working knowledge I was told that in every substation the neutral and earth are combined. I used to work in a university where we had separate copper spikes in the ground for sensitive equipments.
Thanks Steven, sorry about the volume. Two other chaps said the volume was low and others said it was ok. However, that video was recorded with a brand new microphone so perhaps it is that. I've not used that mic since. Yes, at the substation the earth and neutral are physically connected together, what we call the Star Point.
Thanks for watching, we shouldn't have that problem again. Dave.
@@learnelectrics4402 it's not a problem, if people don't tell you then your non the wiser, thankyou for your great output here. 👍
20m of 10mm swa is £143 as of yesterday and what would it cost for a 50A rcbo?. no ill stick with 6mm for now.....lol world gone crazy!
Thanks for watching. Dave.
couldnt hear most of the video due to sound problems. Any one else got sound issues?
Nope, sounds just as normal.
Thanks Zed Zed. Dave.
Thanks Chris. You're the third person to comment about sound quality. Most people seem to be ok but I will check it out. I did use a brand new microphone for this video but nothing showed up when I replayed it, more investigation needed and another new microphone by the sounds of it (sorry about the pun).
Thanks again. Dave.
If I had the iPad in one orientation the sound dropped to a very low level. If I turned the iPad 180degrees the sound was ok. Very strange, not experienced this before
Regs state sub boards minimum of 10mm .also .swa cable armour sheath can not be used solely as a earth conductor a separate earth cable not less that 6mm must be used. Rcd and rcbo mcbs must also be used to disconnect the supply. And most importantly all the electrical installation must be carried out by a competent person tested and the results sent to the revelant governing body.. do not watch you tube videos and think you can do it ..electricity is so dangerous and done wrong can result in death.
Thanks for watching. Appreciated. Dave.
😔 P*R*O*M*O*S*M!!
Thanks for watching.
Sound is very low
Interesting. Are any of the other videos low. Thanks. Dave.
@@learnelectrics4402 others are ok. And the prerole ads are full volume, so I don't think it is my phone.
I don't get it. Loads of 'sparkies' on YT installing earth rods for garden rooms at the bottom of the garden. .. It seems like a grey area to me as no one can agree - similar to politics..
We're not as bad as politicians are we. Thanks for watching.
When researching electrical installations on boats supplied from the shore it was generally recognised it is impossible for an installation to be 100% safe. We have to settle for making the best of a bad job whenever it involves electricity. Correct/wrong??
It says in building regs that a property with a TNC-S earthing arrangement (PME) can not have the earthing from the house exported to an outbuilding, instead the outbuilding must have a TT earthing arrangement. That also means the PME at the house must not bridge with the TT arrangement of the outbuilding (shed/garage) so what you’ve said there isn’t correct with a TNC-S swelling.
You are right and if you watch the video again you will see that we do not export the TNCS to the outbuilding. There is a difference between TNCS and TNS.
Thanks for watching. Dave.
At 5:18 when you say 4 mil cable "might" be sufficient - presumably that is without doing the volt drop calculation ?
This was just part of the general conversation, yes you would do a Volts drop and you "might" start with a calc for 4mm.
@@learnelectrics4402 One thing I forgot to ask - as 5.42 you talk about the suitability of the steel wire armouring at 4 mm sq yet at 8:09 you appear to contract this.