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👍
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?
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!
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?
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?
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)
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.
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
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.
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.
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.
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 ?
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!
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
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.
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
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.
+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...
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.
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.
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.
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.
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
JohnMy assessor told me that if an outbuilding is more than 20m (footing to footing) away from the house then an earth rod must be installed. Is that correct? Thanks
In a way. There isn't a specified distance, but as you get further from the main property it makes more sense to have an additional rod rather than to rely on what could be a very long cable.
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...
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.
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?
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.
I am also against exporting an earth from a tncs I was under the stars impression that you can not export it from the main building as if you lose the neutral somewhere down the line you have also lost the earth conductor I always stick a rod in an outbuilding on a tncs system I was speaking to s guy who is involved with the regs and he has told me that they are talking about trying to make all tncs into pme as there has been too many problems where the neutral has been lost with the supply so there is talk of having to rod every house in the country that is tncs or something along them lines
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?
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?
+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.
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
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?
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
I would of thought using a submains to an outbuilding with a PEN is absolutely last resort. It's essentially increasing the consumer mains PEN, thus any issue with continuity is bad news - why take on the risk?
Depends what they were referring to. It can be used, but only if of suitable size, 10mm or larger. There are many installations to outbuildings which have smaller cables, and for those the earth conductor would be too small to use as bonding.
John Ward to confirm, TN-C-S at origin and a 3C 10mmsq SWA feeds a shed containing extraneous conductive parts, can the internal 10mmsq Earth be used? On a forum, someone has described the scenario as 'its about the exported earth being possibly at the potential of star point which could in fact be many miles away'?
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 ?
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??
Mate, I got 1:45 into it but realised it was going to take 17 more minutes of my life for you to impart about 2 minutes of factual information about the topic I came for. 90% irrelevant waffle.
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
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)?
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.
If 6mm is large enough for the loads, voltage drop etc. then you could. However the difference in cost between 6mm 4 core and 10mm 3 core isn't likely to be significant.
+John Ward Why isn't there SWA provided with 10mm earth and 2* 4mm or 6mm cores, to cover this situation? Workaround seems to be 2-core SWA, with parallel 10mm Earth wire, but then you have problems deciding if the 10mm cable is/isn't sufficiently protected by being in plastic-conduit / ducting all the way outside...! Any Guidance on this situation?
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
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.
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.
Rather than using 3core SWA at 10mm2, can you not use 6mm2 and use the third core AND the armour for Earth to make up the deficit? (assuming 6mm2 is enough for the L/N conductors too)
No, as 6mm² SWA has steel armour of about 23mm², but as steel is about 8 times less conductive than copper, the 23mm steel is only equivalent to about 2.9mm copper, 6+2.9 is less than the 10 required.
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.ThanksPeter
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.
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.
John, thanks for this. You did not explain why the earth cable needs to increase from 6 sq mm to 10 sq mm if there were extraneous parts. I presume it is because more current needs to be carried .... but why?
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.
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.
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.
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....😮
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.
Hi John, I was always told that if you couldn't touch the outbuilding from your main building you had to divorce the dno's earth and use a TT rod for the earthing system, do you think this is something that the dno stipulated years ago ? taa
Would the 'spare' core of a 3 core 6mm SWA combined with the armour be acceptable as equivalent to 10mm earthing? Great Video by the way as with all your content!
Generally no - 6mm² 3 core SWA has armour of about 23mm², but that is steel which is about 8 times less conductive than copper, so only equivalent to 2 or 3mm copper, still below a total of 10 when added to the 6mm copper core.
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?
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.
if you run your copper water pipe from your house to your garage or shed wouldnt the earth from the house cover this as its directly connected. You would only have open circuit on the tap earth in the garage if the water pipe was physicaly broken.
Hi John. Great video thanks. I see a lot of talk about exporting a PME as a big no no, but this contradicts what you have said in this video. Any thoughts on that? Thanks again.
John, A really useful video as usual. Thank you. However I am not quite clear what connections are appropriate at the house and at the outbuilding in the different cases you outline. Is the connection at the house always through the house consumer unit? And is it ever appropriate (or indeed permissible) to install a separate consumer unit in the outbuilding? And if the answer to the second of those questions is "no", how would you connect, say, a lighting and a power socket circuit at the outbuilding (which must be a common requirement)? I guess these might be subjects for another video. Indeed you may have done one, in which case my apologies for missing it!
All depends on what is to be used in the outbuilding. Can be a separate circuit, or an extension of an existing one. A consumer unit can be fitted in an outbuilding but this is not essential - things such as lights could be connected to a 3A FCU.
@pmailkeey on ceramic pots? Then again my GFs house is fed that way, 2 bare copper overhead conductors onto ceramic pots with meter tails outside, (TT system) Need to check what my shed is, I believe its fed with a 2 core MICC cable from a 16A 30mA RCBO in the distribution box assuming that the copper cladding is the earth
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.
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.
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
Great videos. Really informative. Would i be able to use the 10mm2 earth cable separate for a hot tub outside? Or does that definitely need to be set up as a tt system? Im on TN-C-S
You can do that for a hot tub, although the regulations recommend that an earth mat or electrode with low resistance is installed even if TN-C-S is used, so there won't be much difference in cost or installation time. The electrode/mat would need to be connected to the TN-C-S earth via a minimum 10mm cable.
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
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.
So, John. I have a (single PH) 2 cable overhead supply into to a brick building, where the meter is. I need to go from there (via rcd spur) underground 75m to my new house, which will be, yes, steel framed. About as Extraneous as it gets.. What do you feel is best? With the long run, I was going to use 25mm sq cable, but 2 core, as I feel relying on such a long (and old, unknown) earth is maybe risky?
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
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?
John I have just recently put up a metallic hut. I know this will need 10mm bonding as it's a TNC-S configuration at my cable head. Can I take the 10mm bonding from the water pipe in my kitchen which is at the side where the hut is? Or do I need to take it from the MET or consumer unit which is the opposite side of the house and would mean lifting flooring and stuff? Kev
John this is very interesting . I hope you will see this as I am kind of late to this , it is 3 years old! . I have a question , or questions for you if that's Ok? . I am "into" lights , especially old street lamps and have installed a few old , restored , cast iron street-lamps in gardens for people . My question is , would a metal lamp post in a garden, remote from the house, often some considerable distance , need to be treated the same way as an out-building , as if it WERE an out building ? (Albeit a very "narrow" thin one)? In the past I have always used a relatively small cable to supply lamp posts in gardens like this , (probably a 1.5mm2 three-core SWA) . In the base of the lamp post I would normally connect a bonding conductor to the metal body of the post itself , (often by drilling a hole and fitting a brass earthing bolt). This would be connected to the earth terminal in the fuse / cutout which would be connected to the earth-core in the SWA cable and the armour wires. However , if I should be treating a lamp post as if it were an out building, and applying what you say in this video , that would mean I would need a minimum 10 mm2 SWA cable , or to provide an earth electrode for the lamp post? Is this correct? Have I been doing these incorrectly? How would you install a metal lamp post in a garden like this? Would what you have discussed here in the vid apply to this? Regards . Jerry.
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 😀
Surely most people will want to fit RCBOs or RCDs on all new installations anyway, so TT is the basic way to go to satisfy regs easily. If you supply with say 6mm SWA 3-core and link armour and earth you have more than enough safety at reasonable cost.
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.
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?
in a TT system, one should not have more than one earthing point to avoid ground loops which depending on the fault can cause power to flow from one ground point to the other, which is why the electrical code in my country requires that all earth wires go to a earth bus bar within the DB, before a single earth wire goes to the earthing rod. No looping of earth wires is allowed. So by right, the outhouse should also have an earthing wire going back to the panel in the main building, if it was a TT system
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
@John Ward, Could you please do a video on generator installation in single phase domestic places? Pertaining to the earthing and neutral connections at the actual generator and connection to a switchboard, via a transfer switch. There are a lot of American videos here, but none from the UK or NZ. Our regulations and "standards" here have made something like this, damned near impossible to find any real information as to how this should be done. What I'm after is the theory behind doing such a thing.
Hiya John. My mate has torn down his wooden shed which had power supplied via swa cable but he's gone and bought a metal tool store to replace it. It isn't sitting on the ground; rather, it sits on decking. What are your thoughts on this arrangement? He requires a socket outlet fitting for gardening purposes etc.
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?
why you woudnd take a pe line from blue building to main building and use the ground at main building in tt system ?? there is nothing special i see to make problems? at a steel armored wire use the armor as pe?? what is about corosion of steel? byside i only like TN-S-System systeme with symetrical squersection of conducters or better a bigger PE! all other are syspect to me!
