Earthing Systems for Outbuildings

[@PhatTony-km3fl]

Great comprehensive, well presented video John, it has covered the info I was after for my son in laws project on his new house and man cave (A "TT" installation as it happens) Many thanks👍

[@harryadknee3980]

Thanks John for an incredibly clear and informative explanation. Good to see a You Tube video without bells, whistles and wrapping paper! Just straight to the information required.

[@itmayjustwork]

Thank you so much for making this. Your description is excellent and extremely useful. You made it sufficiently understandable. Great work.

[@iwayini]

Many thanks John for your fantastic videos. This video was very informative.

[@torquaymark4155]

A great video. Clear, concise and thorough. Thank you!

[@Plumbermark]

Certainly clears up the jargon and diagrams in BS7671....Wished i watched this before college ! lol now it's in my head so thank you John as always !

[@karl3721]

Thanks John excellent video, settles an argument I have been having with some young upstart who is telling me I have been doing it wrong for years.

[@Graza25]

"Your house might even have a roof on top", OMG, you crack me up John.

[@bramcoteelectrical1088]

Remote power to sheds and out buildings on PME/TNCS is the bigggest head ache but John nicely clarifying things for new sparkies and anyone diy 😊. Great work and clear as this is often debated and argumented....😮

[@Badgerooni90]

This is so clear and easy to understand. From a fellow electrician. Thank you

[@SzDavidHUN]

My grandfather have some talent for electronics. Replaces the ungrounded power outlets with grounded ones, does not connets it to anything (at least he says), and there is 115 and 81 volts to main and neutral from the ground. If I connect my aplifier to the living room, the speaker in the bathroom give me 81V to the case of the washing machine. The next rooms power outlet works fine. It MAYBE connected to the heatin systems radiator. The taps earthing is removed. In the garage we have a power outlet which have main on both terminal. Makes extension cord from 3 color 4 core wire, uses the same color twice. Uses 3 core wire, metal case machine, earth plug, leaves earth wire long and not connect. Doesn't use the strain relief in the plug. Maybe I sould be or get an electrician and redo the whole wiring.

[@mx5mke]

0:56 "Your house may have a roof on top" ==> (giggle) "British, much, lately?"

[@thermion7869]

John, Thank you for a very good explanation of the requirements for different supply systems.

[@shiamjad]

Thank you very much for your service to the industry.....Learnt so much from your videos

[@ekner]

This couldn't come at a better time. I've taken on renovating an old outbuilding on our property and I know I'm going to have to at least add an earth to make the wiring safe.

[@aurora0257]

I solved the problem of getting power to my shed for lighting by fitting a 12V solar system £100 for a 40w panel & charge controller, £15 for two 12v 10w LED floodlights and a used car battery £0.00. Six years later and it's still working fine. It would have been too much hassle to correctly run a mains supply to the shed which is mostly galvanised steel.

[@deborahholmes7465]

Thank you John.. perfect explanation!

[@lesterelectronics223]

If i install an electrical system in an outbuilding containing extraneous conductive parts, with the main building being TN-C-S, I always install an earth rod at the outbuilding. If there was ever a situation that the mains neutral was to become lost or damaged the earthing can become live at mains potential, which could be dangerous. This would not be a problem at the outbuilding if you made a TT system. I understand that you have multiple earthing steaks on a PME system, so if there was a break in the neutral the system can still be held at earth potential. However if the neutral break was between the last reliable earthing point and the customers home, any extraneous parts will become live at mains potential. I know the chances are slim but its possible. I have looked at the draft of the 18th edition, it looks like we will have to install earthing steaks on all new installations whatever the earthing system. I believe this is because of the points raised above.

[@sbusweb]

+Lester Electronics Additional earth rods would have to be very low impedance to make any significant difference, I thought... In my view some kind of "PME lost neutral detector/3-pole-disconnector" might be needed...

[@pauldavies9709]

Chances are your own house has a PME supply head and I doubt you've TT'd it, why would you bother treating an outbuilding any different?

[@atanquerel]

@R-77 no.

[@tinytonymaloney7832]

Been out of the trade a few years, semi retired, but I had to watch this to recap. I remember in the past I always used minimum 10mm SWA 2c SWA as standard and I don't know why or who told me to and I always used an earth stake completely isolating the earth connection from the house. Also I was taught on PME the mini C/U had to be plastic. I'm going back 30 or so years. Only recently have I seen vids of people connecting and using the house earth in a shed or outbuilding an wondered when this changed. Like we had to earth bond everything in sight at one time now its not the case. Glad I'm out of it now, just do bits at home spurred on after much nagging from her indoors 😀

[@antoniosfares3888]

Particular care is required where conductive pipes and such items as telecommunication cable sheaths , covered walkways, etc may be continuous between separate buildings and thus establish a parallel earth/neutral path

[@ChaoticaExtreme]

If you only need modest power requirements for your outbuilding, say lights and a pond pump, then treat the outbuilding as an appliance. Simply connect to the house supply via a standard plug in a convenient socket. Your outdoor wiring is no longer a permanent installation and is treated as an extension lead. Obviously, the connecting cable should be suitably stout to handle the max possible load rating of the plug, even if only as a fault condition. I would still use a small consumer unit in the outbuilding regardless, and protect the connecting cable. Not what you are teaching here, John, I know, and thank you for it, but jogged my memory and I believe is worth keeping in mind.

[@JimWhitaker]

Exactly what I did.

[@sagranreddy5696]

THANK YOU JW...for the detailed yet easy to understand videos.

[@joefarr3304]

John, thanks for this video and answering some of the questions below. This has really cleared up confusion I had around TT and the earthing that the electrician put in when he cabled my home office. He didn't connect the armoured cable armour to the outbuilding earth (there is a separate rod) or fit a time delay RCD at the house end. The breaker often trips when I plug in a laptop PSU and have to go dashing off to the house to reset the breaker. I will be having a conversation with him tomorrow.

[@Gary-ts6dh]

I'm glad you didn't title your video "Earthing Systems for Outhouses". That said, I can see a ground loop possibility between the two buildings as a result of the ground rods not being close enough to earth potential within mΩ (i.e., one of the rods has not as good a contact with the earth due to difference in backfill materials).

[@munchingfoo]

John, I am trying to work out the difference between connecting a TN-C-S earth to a metallic outbuilding and the situation everyone is concerned about with EV charging in the event of an open PEN fault. The two circuit diagrams side by side look identical to me. Any pointers as to why the metallic outbuilding is okay but the EV charger is not?

[@BlackHarleyRider1]

Thank you for a very clear explanation video on the types of earthing...Now to check out your other videos...

[@craigrollinson3326]

Brilliant video John, you make things easier to understand. Please could you do a video of potential difference.

[@neilwilliams3657]

bloody brilliant John, your videos are informative and easy to understand, do you mind if i share with students? I work for a college?

[@davidmg1925]

Mr Ward is the only person who can tell me this stuff. If my Dad starts explaining it I go into a deep coma lasting several months.

[@jafarsunny1762]

J W YOUR VIDEOS ARE VERY MEANINGFUL,THANKS.

[@jafarsunny1762]

Your explanation is very clear.Thanks a lot.

[@johnyearsley7970]

Really informative John. Thank you.

[@gp2580]

Great stuff again John, thank you.

[@daveperryman8554]

Hi John, many thanks for another great video. May I ask how this applies to a metal control box? Would it be a TT arrangement as the box itself is like a metal outbuilding? I am looking at running power to a painted IP65 metal control box to facilitate a supply to electric gates to my house, and am curious as to how this compares to the outbuilding scenario you've mentioned. I am using an electrician for this task but i'd like to be in the position to understand what he is doing and to be able to ask the right questions. Thanks in advance!

[@jamesgrimwood1285]

Put your hand up if you've ever lived in a UK house where the garage wiring was a piece of twin & earth run from somewhere in the house to the garage... Now, my question relates to network cabling... If I wanted to run network cabling between my house and garage (assuming said garage was correctly wired for mains), do I need to do anything special to isolate the network cable between the two buildings? Is it likely that a potential difference between the two buildings would build up, and use the network cabling as some sort of return path, doing horrible things to the network devices? Or is that only an issue for buildings far apart from each other, on totally separate power systems?

[@jwflame]

Not a problem, all Ethernet cables are electrically isolated by the devices they connect to.

[@jamesgrimwood1285]

That was my understanding too. So what are the "ethernet isolators" for that you can buy? Is that in case the cabling itself somehow picks up a charge? (which is unlikely in a short 20m run from a garage to a house)

[@LunaPlanetside]

Shielded ethernet cables are bonded to the earth of the devices on both ends, so some current could flow down this if you use shielded cable bonded at both sides. It would effectively be in parallel with the the earth used to supply the outbuilding. The isolators (often seen in hospitals) are typically rated for a higher isolation voltage, and isolate the shield.

[@jusb1066]

sure ive seen a lot of garages that have been using a standard extension lead for decades, running it outside along the fence in all weathers, plugged into a spare socket, then wonder why they cant run much at the end of a cheap 30m lead. dread to think how standard flex it stands up to UV and british weather too, my garage was built after the fact of concreting nearer the house, thus could not bury the cable, but in the 80s we wired at along the fence with MIC pyro cable, have had no issues in 30 years, we also have an earth rod along with the pyro is earth in the outer

[@boriseng]

There are different degrees of isolation. A typical port has a rating of 1500V (which is a TEST voltage not a continuous rating) but the industrial isolator I looked up was rated 4000V.

[@1Greghancock]

Thank you, very succinct appreciate your delivery as fast

[@TheChipmunk2008]

Interesting John, thank you for this.

[@grahamrobson998]

Thank you John clear precise and very very helpful

[@diggoryjones7837]

Earthing for off grid using inverters would be useful too. And how to connect to house pipes with grid earthing?

[@Webbster77]

John, so if I have a steel frame pergola in a garden that has lights and heaters attached and wired through the frame it would need bonding accordingly as well then?

[@digitraxuk]

Thank you John for another very clearly presented topic. With a TT system in the main house would it only be beneficial to connect the 10mm 3core SWA cable (cpc) to the outbuilding (with water and gas services) consumer unit MET where it has its own separate earth rod. I would imagine this setup, rather than keeping the two completely separate as you presented, is beneficial in trying to keep the Ra to a minimum. Or is it a pointlessly small benefit since you are relying on RCD for earth fault protection? I hope that makes sense? Many thanks for my crazy brain working overtime.

[@davidceredig-evans8772]

Excellent video again. Many thanks.

[@sbusweb]

Interesting case for bonding -- if you feed an outbuilding with Unshielded ethernet, and also separate SELV power (e.g. monititoring/alarm) in separate conduit -- all metallic, coming in from outside, but have no ''earthed'' wires at all ?

[@shilks8773]

Then you have created an Extraneous conductive part into the building.

[@garrymurphy5555]

@@shilks8773 Could you include the 10mm² Earth cable within the conduit ?

[@tonylynessable]

Hi John.. A great video as always. Could you answer a question for me please... Recently out looking at a job where a new build house is going in.. The supply cable for the new build is actually coming from another house on the site (parents house) So they're new house is titled as an annexed property... The existing house where the supply cable comes from is TT... So my question is.. If wiring the new build property, would it be best to not use the incoming earth on the supply cable from existing property. And to earth rod and TT the new build separately? Keep up the excellent work as always.... Much appreciated by many...

[@ben8878]

if you have done main bonding in the main house and the outbuilding's water and gas supplies are just an extention from the house do you still need to bond these extrenous conductive parts in the outbuilding as they are already bonded??

[@karoly365]

This is the most enlightening lecture I know of after Gautama Buddha’s some time back.

[@ernstpeterlegrand]

Working slowly through a lot of your videos. I am not living in the UK but living in Thailand. Working here only with TT. The electrician that was involved during the building of the house wasn't very good. So time to check everything. On this video. If I have a rod both at my house and the barn, would it be beneficial to connect them together? The difference is though that in my case, the electricity comes into the barn and with an underground cable goes to the house. Currently it is 2 wires going into the house with an extra rod for grounding at the house. The situatoin is actually a little more complicated but that I will ask in another related video that comes more close to my question.

[@ernstpeterlegrand]

the reason I was thinking about that is that in this way, both ground in the house and ground in the barn are basically a single reference to the neutral.

[@bjtaudio]

Also with equal potential bonding its typically installed as a separate earthing conductor run back to the earth bar at the main switchboard in the house, it's normally not needed to be connected to the feeder earths in the outbuilding as well, But not that it really matters if they are combined or joined to the feeder earths. Its typical to bundle the bonding conductor with the feeders in the same conduit or ducts. If the bonding earth is directly buried, this may be where the 10mm2 min size is coming from, I thought it was 16mm2 however. I never directly bury cables anyway.

[@Mark-ij2nh]

6mm swa 3 core best for future installs. Will support up to 40a mcb at the house and will supply a 32a ring and a 6a lighting circuit.

[@michaelcostello6991]

Why in a TT system does shed need its own electrode in ground. Is it because it would be running beside the 230 Volt cable from house. Or is because a fault in house would send all exposed metal in shed to 230 Volts ?

[@tonyknight9912]

Excellent presentation.

[@01dec2001]

Much appreciated. Would you consider inserting an insulated section in to the water pipe itself, breaking the electrical connection to ground("extraneous part").? This would obviate the need for a 10mm bonding cable and possibly work out cheaper?

[@ciaranhughes8705]

If copper pipes from house go underground and re-enter a ultily room. Does his need additional 10mm bonding at entry at utiliy. The board in ultilty room only has 6mm twin and earth supply. Thanks

[@boblewis5558]

Here's an interesting one: power from an attached garage (where CU is situated) to feed a wooden shed, maximum 6 feet away on a concrete base with concrete path between and a concrete garage floor! Questions 1. Is a catenary supported SWA installation legitimate or MUST the cable be underground? 2. The house is TT so presumably the shed will need to be TT also, or is six feet considered OK to use the same TT earth as the house? Seems undesirable at best to do the latter 3. Presumably also, all circuits will need to be protected overall by RCD anyway or individual RCBO? 4. What are the considerations for avoiding inductive spike loops? The house rod will be connected to the shed rod via the ground and there will be an earth cable running overhead to the CU in the shed. Unless there is an earth break somewhere, a full earth loop with the loop resistance in it will be created. What is the recommended mitigation or avoidance for this? a) Bring the SWA earth connection (3 core cable) into the shed connecting solely to the SWA steel sheath in a separate insulated enclosure and connect the system PE directly to the shed rod? b) Bring the SWA connection into the shed and connect it AND the shed rod to system PE and ignore any possible ground loop effects? c) Bring the SWA connection into the shed and connect the SWA earth to both system PE (including the metal shed CU enclosure and the steel sheath on the SWA and not use a shed rod (due to it's close proximity to the garage and the source power CU)? 5. Presumably NOW (Feb 2020) the 18th edition regs apply and the shed CU must be a metal clad one (earthedto what?) with plastic being non-legit?

[@Richardincancale]

Hi John, two questions: For a TT system would you bond the two earths (house and shed) via the armoured cable? Also - aren't you obliged to use an RCD at the house end to ensure safety in case someone sticks a spade through the buried cable?

[@jwflame]

Yes for both.

[@alanallington1001]

John Ward Hi, thought you didn't need an RCD on the house side to feed the new garage board with its own RCD if its a tn system?

[@jwflame]

+Alan Allington For TN systems the armoured cable does not need an RCD, as the fault current between line and the earthed armour will be high enough to trip the circuit breaker. An RCD is required for TT as the fault current between line and the armour will be very small.

[@alanallington1001]

Hi John, as i said. Seem to think you said an RCD is necessary both ends? My business is 26 years old and still learning, please keep helping this high class industry prospered. thanks Alan

[@boyeselectrical]

Could you use a 6.mm 3core swa and use one of the inner cores plus the armour to make up the difference ?

[@MrSJT]

*Following this comment*

[@sbusweb]

I (think) i worked out that may not in-reality be enough... and in some respects goes down to the regulation-wording. I could also ask after 4mm 4-core , 2 cores + armour to carry the main equipotential bonding? Puzzle!

[@MrSJT]

Come to think of it, probably not as the steel cores would have to be at least 32mm before you even go there, and even then, it may still not comply as it is not one material or the other due to wording of the regs

[@12000gp]

I’d say not because they would then be parallel conductors and a parallel conductor need to be the same diameter, same length and made of the same material to ensure it has the same resistance I believe.

[@islandhopperstuart]

Excellent: just the information I needed.

[@davidchamberlain2162]

I have a wooden summer house with a couple of sockets and a light. I have have connected it to the main house using 3 core armoured cable. It is connected via an RCD and 7 amp breaker off the down stairs ring main. It is all relying on the ring main earth back to the consumer unit. Should there be a supplementary separate 6mm earth cable back to the consumer unit? There are no extraneous metal parts.

[@MS-yy2dh]

How would this apply to a series or outside (earthed) metal bollard lights, screwed to concrete slabs, assuming the house is TNCS earthed? Can the house earth be used (as with a wooden shed) or is an earth rod needed for the lights (as they are metal)?

[@MS-Patriot2]

Probably best to convert to a low voltage system to be sure, see David Savery’s recent video on that. Otherwise make sure the circuit is RCD protected and have the 5X disconnect time checked for compliance (within 40mS) at the bollard furthest from the supplying RCD.

[@firstclass8710]

Hi John. Fantastic video's very informative. I see in the video at 13.55 you talk about ignoring the earth connection and driving your own earth rod. I have been asked to fit a new board in an outbuilding. The supply is coming from the dwelling house is a two core SWA cable and the steel wire was not used as an earth. As I see it I have two options. Option 1: Find the SWA back at the house and use the armour as my earth and connect it to the earthing block in the main board and do the same at the new board. The installation in the house is quite old and the size of the cable from the board to the earth rod is not 10 squared. Option 2: Ignore the earth from the earth connection coming from the house and drive my own earth rod and use 10 squared cable to the new board in the shed. What would you recommend and what distance from the building should the earth rod be driven?

[@hintoninstruments2369]

How can you say 6mm2 or 10mm2 without knowing the distance? If I have a metal frame greenhouse 30m from the house connected with 10mm2 3-wire SWA and the frame bonded to the E and armour the frame is in contact with the foundation, especially when raining, whether another Earth rod is added or not. So what happens if there is a close lightning strike and there is 50kV or more gradient between the house rod and greenhouse frame?

[@geoffdaniel1534]

Hi John I’m doing an old outhouse up and need electricity in it the outside is 2 metres away from electric can you use power from a wall socket to a consumer board and do it in armoured cable or do i need to get power from mains board all its doing is running a frezzer and garden lights thanks again

[@normanboyes4983]

Very clearly explained.👍Thank you.

[@johnwinters4201]

In a TT installation, would you then connect the two earth rods (house and shed) together?

[@Roverturbo]

Here for this reason, did you find out?

[@stevemead5000]

Have you considered using a 4 core SWA 6mm and using 2 conductors joined together as the earth conductor

[@rakselectric7390]

Useful information keep up the good work

[@stevecraft00]

A shop i worked at had a shipping container out back with a light and socket in it. They just stuck a plastic conduit from the shop to the container. no thought was given to bonding etc.

[@JamesEdwards860]

Hi John In relation to exporting a PME to outbuilding, A question I’ve always wondered is why is outdoor socket or lighting ok which could potentially be or have conductive things plugged into it. Yet if the light fitting was fitted to an out building the building would need an earth rod?

[@brucerobson8767]

Hi. John, Can I use a 6mm 3C SWA cable to supply garage with water pipe if the earth core is combined with the armour, TN-C-S system.

[@AdrianMould]

Hi JW, fab as always. A question if I may. I am off grid completely but running a conventional house. I generate electricity approx 100 metres away where it is also stored in batteries prior to onward transmission to the house. The solar system is earthed via a very effective TT install - there obviously is no other option. My earth and neutral are linked inside the inverter/charger. 3 core 25mm runs from my solar setup to my house. I have treated my house electrical installation as having a TN-S system and regarded my solar system (100m) away as my ‘power or generating station’. Consequently, I use the 3 core incoming earth at the house as my main earth, ie. no TT at the house. I wondered if you had any thoughts as to whether or not that is a suitable arrangement. In my head I can’t see a difference from a city estate house and my set up on a TN-S arrangement. BTW I am a retired electrician. Many thanks.

[@jwflame]

Your installation is TN-S. There is no TT. TT would mean an earth electrode at the solar/battery, 2 core L&N cable to the house, and another earth electrode at the house.

[@peterg5156]

Great video (as usual) thanks John.I came across this only recently so I think that the 18th edition change on bonding insulated section pipes may have overtaken the description? I can see that, for the TNC-S case with an open circuit PEN, the outbuilding feeder earth connection plus the 10sqmm connection to the water pipe could carry the entire installation neutral load current. I suppose this would only be so if the house water and gas pipe earth resistances were high and the outbuilding water pipe earth resistance was low. Wouldn’t it be easier to insert a piece of (insulating) hose pipe and avoid having to connect the water pipe to the protective equipotential bonding?I would be a bit reluctant to supplement the 6sqmm armoured cable earth core and about 23sqmm of steel armour in parallel. However, I don’t know if this arrangement would equal the current carrying capability of the 10sqmm bonding conductor? If the d.c. resistance of the armour is about 6.7ohms/km and the d.c. resistance of the 6sqmm copper is 3ohms/km with a current carrying capacity of about 42A, could we assume the armour will have a current capacity of about 3/6.7 x 42 = 18A? This would give a total rating of 42+18=60A - which approximates to the 60A rating of the 10sqmm single core. A bit shaky perhaps - A bit of hose pipe may be safer.Regards

[@curiousmichael]

*So* interesting, as usual - thanks!

[@chrisgascoyne4532]

hi john, After some advise please. i want to daisy chain two outbuildings from a TT house supply, would i need to fit two more earth rods and would they be linked together ? so all three are in parallel ? also how would I rcd protect them ? would it be better to not fit an RCD at the final DB and use the first outbuildings rcd ? no extraneus metal water pipes but the second outbuilding has a hot tub built on top of a metal tank . any help appreciated, chris

[@tavislucaso]

If you’re supplying an outbuilding without extraneous materials or a hot tub, and your have. TNCS system inside, could you just use a 2 core to the building or tub, earthing the armour with the TNCS and then just put a separate cable out to a local earth rod? I’m getting so confused by when to use RCDs with a TNCS system

[@colinmiles1052]

Thank you John, crystal clear.

[@eglkFlyer]

Excellent video John. A question, in the case of a garage with a steel sectional door , would that be regarded as extraneous and need bonding ? Also if I have a brass water tap inside the garage fed with a plastic water pipe, how do we view that from bonding perspective?

[@iainkay3630]

Regarding the brass water tap, if the plastic comes out the ground and is converted to brass above ground then it should not need bonding. If the brass enters the ground at all then you should bond it.

[@PaulSteMarie]

Huh. I'm pretty sure the TN_S configuration is the only type allowed for remote subpanels under the current US NEC, but the third conductor is an actual wire in the cable, not a lead sheath. Mike Holt goes into excruciating detail on this in his videos, which I highly recommend. The TT configuration has far too much ground resistance to reliably trip breakers, and the TN_C_S has the usual sorts of shared neutral/earth issues. Notably a broken or high resistance neutral/earth connection will result in all grounded metal cases going live in the outbuilding as soon as any thing in the outbuilding is turned on.

[@mr.d7372]

Questions: I have a metal lamp post outside currently supplied via a 13A spur from an interior ring going outside via junction box to SWA. Not sure what your opinion on that set-up would be .. but my main concern is possibility of lightning strike to the post sending a current back into the house. Is there any reason not to disconnect the exported earth at the exterior junction box and replace the earth with a rod?

[@station240]

Related question, how to you measure the stray voltage generated when there is a bad Earth bond ? I know of a commercial building with a stray voltage on anything earthed (sometimes). Thinking I have to report it to power company, as multiple transformers involved.

[@Nispark]

Hi john With lots of these steel sheds that are going up now would it be better not to bond the steel frame as they sit on a concrete base and don’t bring in a potential or tt and bond steel frame? Tia

[@MrWeddingPhotography]

On a tt system, I don’t understand why you would need a second Earth rod in the ground for the garage if you took an Earth from the house.

[@barrybritcher]

from what I get from the video you dont need it - only if there is extraneous metal parts

[@Jck142]

If you have a TN-C-S or TN-S supply to the house and your taking an earth to the garage there would be no need for an earth rod. As this would continue as a TN-C-S or TN-S system, providing the CPC is appropriately sized.

[@kiewong4870]

Jck142 extending the tncs, to an out building, if the neutral goes down, are you not out the equipotential zone? I thought you are, and this is why you don’t use the pme and simply rod it. Slightly confusing. Many people say only use one system, I’ve also read and been told, you can supplement pme with rods. I.e a cabin wired in swa, using the pme, can be supplemented with a rod( in case of neutral fault). Under fault the currents can be large and burn the rod out! So unsure about this too. Very conflicting, wonder if @johnward

[@MrSJT]

Moelwyn, he answered that question elsewhere on this video amongst the other comments, you can export so no need for another earth rod

[@termite2691]

What's the difference between touching the floor of an outbuilding with a concrete floor, which is the "ground" is it not if the concrete is in direct contact with the earth below, and touching a tap connected to the ground through a metallic pipe ? Surely in both cases you're touching ground ? Or is this just a case of how good the connection is as a conductive path ?

[@ColinDH12345]

With the 18th regs I believe you will require an earth electrode anyway even for TN installations. In which case would and exported earth to an outbuilding require an electrode as well? Rather like a belt and braces approach I guess. Very useful video.

[@jwflame]

The 18th is only a draft, but one electrode at the origin (in the house) should be sufficient as you are not installing a new supply but just extending an existing one. You could install one if desired, and the existing 17th edition does allow this already.

[@ketas]

we use earth rods and bonding because that brings body standing on ground or touching objects into same potential with equipment case's pe and no dangerous currents will flow now you stand in your shed but your pe comes from far away house and has no local connection to actual earth under your feet. that sounds bad even with rcds which would limit fault voltages. if it's any permanent installation i would recommend replicating house's system in there. that is, if tn-c-s, bring either tn-c or tn-s to shed, and ground your pen or pe there. logically thinking, it would be even safer if you ground something that should be at ground level anyway if you dig the cable into ground and path to shed is short, you could improve both buildings earthing by installing vertical and / or horizontal earthing structure along your cabling. if, for god forbid, the buildings miss earth altogether, you could end up with proper electrical system too. later could be case, depending how strict checks your country has. estonia, where i live, doesn't currently have strict checks on existing installations, it's both good and bad

[@jeffeloso]

Would using MICC cable be a solution to the size of the earth conductor - yes I know you need specialist tools and training to make off the ends successfully, or does this not give adequate protection for buried cables, or should then this be run on a surface instead if possible?

[@astrofishwalk]

I am thinking about having the house consumer unit upgraded and wonder about adding a separate supply to my garage come workshop. Currently it's a spur off the upstairs ring main as that is lightly loaded. The spur is overhead swa and meets requirements on that but may be changed to buried. I aimed to treat a new feed like a sub main by using fuse protection to allow the remote consumer unit to function independently of the main house circuits protective devices. I'm wondering if 18 strictly prevents the use of a PEN produced at the garage cu with the resulting earth also connected to a spike. This seems to be a pretty common way of distributing power but not sure how this fits in with building regulations. I feel that this offers a better solution to making the garage purely TT and an alternative to exporting the house earth. Thanks for your videos by the way. I've watched a number of them. They are very useful.

[@astrofishwalk]

I wont be doing the work myself by the way.

[@jwflame]

You can have your own earth and connect it to the supplied earth - there really isn't much point but it is permitted. A PEN conductor (where the earth and neutral are combined) is not permitted within any installation and hasn't been for many decades.

[@astrofishwalk]

@@jwflame Thanks. I wondered as it could be a better arrangement than the workshop being TT. A number of people with similar hobbies to mine seem to end up with TT.

[@alanpartridge2140]

For a TN-C-S system is it permissible to use a 3core SWA with cores less than 10mm^2 but use the steel armouring in combination with the earth core to make up to the 10mm^2 copper equivalent that is required?

[@jwflame]

No, if using steel it would need to be about 8x larger as it is less conductive, so 80mm. No armoured cables under 10mm have armour anywhere near that size.

[@chas3997]

It has been said before that a breakdown in neutral supply can be mitigated by a parallel earth connection In terms of touch voltages being safer. Finally there seems to be more acceptance of this in the new regulations.

[@brucelaing4478]

Great video john any chance of explaining how to wire a second outbuilding is it ok to take feed from first outbuilding or run separate cable from house cu .

[@westinthewest]

I'm planning to run a TN-C-S supply to a remote building (no extraneous metal) from a socket circuit in the dwelling. The new cable will be RCD-protected from the house so I'm planning to use non-armoured cable. It's a 30m run attached to a sturdy boundary fence. How about using PVC conduit containing 6491X singles?

[@jwflame]

Could be done, although fences are rarely sturdy or suitable for permanent installation of cables. SWA will very likely be cheaper and quicker to install.

[@westinthewest]

@@jwflame It's a wooden fence but luckily the base panels are concrete. Whenever I think of SWA I remember the tedious hours spent assembling the glands in the rain, but yes I think you might be right. SWA will be much quicker to erect than conduit, and the summer isn't over just yet (hopefully).

[@TheEulerID]

An answer for that TN-C-S water pipe issue will be to replace the section that enters the outbuilding with plastic pipe. The bonding issue then doesn't exist. Of course if the water was supplied via a 15mm copper pipe, with the standard wall thickness of 0.7mm, it has a cross-sectional area of 33mm^2, far greater than any earth bonding cable. It would require a continuity and resistance check back to the bonding point at entry to the property, but as electrical regulations seem to ignore these real world situations, it's not allowable. So, replace that last bit of pipework with plastic. Cheaper and easier than running 10mm cable out to an outhouse just to meet a bonding requirement.

[@alexwade9921]

In my workshop I have a water pipe which is plastic MDPE pipe coming in from the house (about 10m away) via an underground duct (4” soil pipe) with the armoured cable. Since none of this water pipe is conducting to the actual earth, is it OK not to bond it? What if I took it outside the workshop for a hose tap? The system is TNS and the outbuilding earth is from the house along SWA.

[@jwflame]

Plastic pipes do not need bonding as they are not conductive.

[@joegolden5214]

Just a question. I'm about to connect an earth to my old TT type system, as I have no earthing. Also putting armored cable to shed 10square. Separate rod for shed as u advise. Can the two earth rods be linked at both boards? Thanks John

[@busman2000]

If you do have a stake then you use that as your only earth, as you would create an extended fault loop, if you were connected to the houses earth also..?

[@mjl3691]

Hi John, I have just had a summer house built in brick, with a metal roof, however the metal roof is separated by timber joists, and 18mm decking OSB, so, the inside is totally isolated from the metal roof. I have no gas, or water installed in the building, or steel lintels, etc. I have a 3 core 2.5mm SWA from the house to a new consumer unit located in the summer house. My question is ?? do I have any issues, or requirements with the installation of the ceiling x 2 and all the walls being foil wrapped insulated on the internal wall surface ???? In this order : Brick, Foil insulation, Timber batten, Vapour barrier, Plasterboard & Skim. Regards, Michael

[@jwflame]

No. Roof isn't part of the electrical installation, and it can't introduce any potential as it's not in contact with the ground and it's not accessible inside either. Same applies to the foil - it's a concealed part of the construction.

[@mjl3691]

@@jwflame Thanks for that, also, can the foil perhaps interfere with any smart plug reception ??

[@jwflame]

@@mjl3691 Possibly.

[@kevinallen9106]

If the you TT the outbuilding would you common the house supply earth to the outbuilding rod (two cases of TT house or TN house)? If so is there a maximum house-outbuilding separation required to avoid differences in earth potential? Any other considerations if water (or other underground services) are to be installed in the outbuilding? Thanks!

[@jwflame]

If both the house and outbuilding are TT, they can be connected together, they both remain TT and the benefit is that the earth electrode resistance is reduced. if the house is TN, then they must be separated, otherwise you just get a TN system with a supplementary electrode connected. That is permitted, but it's not a TT system. A TT install must be separated from anything connected to the TN supply, and for buried items such as pipes, cables and similar, the distance will need to be several meters at least, some DNOs recommend 10 metres. If there are other services to the outbuilding, then ideally they should all be plastic. If metal, it's essential that they are not shared with the main house or any other property with a TN supply, otherwise it's the same as connecting the house and outbuilding earth system together and you just get a TN system with a supplementary electrode.

[@SqwarkParrotSpittingFeathers]

Hi John. I need 10mm for the bonding. Let's say I got 6mm 3 core of swa coming into my garage. If I used a copper core for my earth could I combine that with the steel on the outer sheath to increase the earth size. It would now be close to the 10mm required? If not quite there, just to be absolutely compliant would I be able to stick into the ground a small TT rod, that in combination with the steel and the copper takes it to an equivalent 10mm? And I guess that a small garage consumer unit with a RCD would help with the safety of the installation?

[@jwflame]

In theory a core + armour can be used for the bonding conductor, but in reality 6mm² 3 core SWA armour is too small, usually about 23mm² steel which is equivalent conductivity to 2mm² or 3mm² copper (about 8 times less conductive). Note that the 10mm² minimum only applies to TN-C-S supplies, it can be smaller (6mm²) in some circumstances for other supply types. An earth rod is of no use - bonding and earthing are two separate things, one cannot be used as a substitute for the other.

[@SqwarkParrotSpittingFeathers]

@@jwflame Thank you for your prompt and detailed reply. I've been watching your tutorials for three years now. They helped me through college and still do today. They hit the mark regarding my continuing education. Thanks again.

[@starky497]

Hi JW, If the outbuilding is less than a meter away from the main building would you still need another earth electrode (assuming the main building is TT, and the cable supplying the outbuilding is RCD protected at the main building end)? The circuit into the out building would be supplied via 3 core 2.5mm SWA (from a 16amp MCB) and be supplying a 2.5mm radial circuit of not more than a few meters in length.

[@bramcoteelectrical1088]

I would say not

[@Yes-ng6rf]

Great video JW, now I see why you guys call us "convicts", we would certainly be "convicted" if we ever used the armour or lead sheath of a cable as the earth, that's like using the steal conduit for the earth. M.I.M.S cable is one case where we are alowed to use the sheath as the earth and so long as the cable originates at the main switchboard in a M.E.N system, we can also use it as the neutral return path in what we call an E.S.R (earth sheath return system), where a single core M.I.M.S cable provides all three functional conductors to the sub board be it in side the main building or remote.

[@hmmmnz]

i miss wiring in nz and oz, far less stupid stuff, like ring circuits, fucken swa cable and multiple earthing systems and some of the dodgyest fuse boards known to man, dont even get me started on chiseling brick walls to bury cables in.

[@richardwallace3477]

Very useful synopsis - thanks. How about running a 10mm bonding wire in parallel with a smaller SWA cable if you have an extraneous conductive situation in the outbuilding as this would keep the cost down?

[@jwflame]

In theory yes - but if buried, 10mm² requires additional mechanical protection. 16mm² does not but that costs significantly more, so in reality the cost savings are minimal.

[@ducatimjc]

Cheers John. This seems to be a bone of contention in the sparky world. The DNO don't like you exporting their TN-C-S earth even if your outbuilding doesn't have extraneous conducive parts. I've rang the East Anglian DNO and they said no. However NICEIC technical helpline say crack on, or at least they use none committal wording in that if you think the TNCS earth will be better than a TT rod then use it. Seems to be contradictory. This is also becoming an issue for car chargers. Some car chargers say they have built in tech to allow for exported PME earth but again, DNO say no to using it. My personal opinion is that installing SWA correctly, losing the earth core is more unlikely than damage to a TT rod earth/16mm cable (which already could be up to 200ohms) but if the DNO are insistent then TT it is. Whats your thoughts please?

[@ChrisTheSparky]

He's still thinking