Earthing & Bonding - Part 2 : Main Protective Equipotential Bonding
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- čas přidán 24. 05. 2015
- Part 2 looks at main protective equipotential bonding, why it is needed, the size of conductors to use and what needs to be connected.
Earthing part 1 : • Earthing & Bonding - P...
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NO daft intro or music, just straight clear facts. Fantastic.
I congratulate you Mr Ward on (yet) another first rate presentation made with wisdom, clarity and humour, thank you!
You sir have just earned a new subscriber.. Fantastic info thank you
This man is a mean machine...wish I had him as a lecturer when I did my training...keep it up...love your attitude and zest for explaining things
Hi John, your videos helps alot, thank you ever so much for making them. If You can pls make more videos explaining various sections from the BS 7671 book pls.
Thanks John for another concise and informative video. Easily the best resources available for revision.
Sheer excellence. Many thanks for these videos that are very clear and well explained with justification of reasons.
Re. Metal CH pipes set in concrete. As copper reacts badly to being directly embedded in concrete, any such copper pipe should be wrapped or sheathed. You can get 8 & 10mm microbore pipe with with a semi-airspaced sheath to give some thermal insulation as well as isolating it from the concrete, which should mean it's not an ECP. I wonder how many electricians would pick up on this point.
JW, Thanks for the vids. You are one of the best tutors on CZcams. I have watched a lot over the years and few can compete. In addition, the section about the boiler causing shock when touching hot and cold pipe has possibly solved a 20 year mystery of an incident I dealt with in my old job. Thanks.
Hi JW, firstly thanks for the video ! Just a comment on the several good folks discussing whether or not to bond things in domestic situations. I have been zapped, several times over the years and all of them could have been avoided with proper bonding as you have described (I started work in 1974 and things were not well controlled shall we say ). Noting my bias, if it's in someone's home, if it's an accessible copper pipe, I just want to see it bonded. It doesn't cost much and then there are no surprises :)
Awesome video thanks for the lesson, much easier to learn this way as a pose to reading it.
The video is excellent. But I think the "why to use protective equipotential bonding?" part should be at the start, then followed by examples and details like conductor sizes and types.
Big thank you JW!
JW is my best channel. Because his is smart and English
Really useful video as per usual! A very belated comment but if my understanding is correct: it should be Emphasised that: an "Extraneous Conductive Part" is not only some "externally supplied (metallic) service" like water or gas. It applies to ANY metal object that comes into your building (from the "real" earth). Which includes but is not limited to your gas and water supply, eg: it includes your own off-grid water tank, if it has metal pipes. It is any metallic object connected to the "real" earth that you could touch at the same time you are in connection with a fault in your electrical installation. It is about "Equipotential": so the Earth in your electrical supply and the Earth in your metallic pipe may have a different voltage potential. This difference could kill you (and also why an RCD is essential as well). In a "TN" installation these should all be bonded together to make the system earth and ground earth at the same potential. In a true off-grid TT installation you need your earth rod(s) close to the point of contact to minimise this potential difference. eg: I have a TT supply coming into a metal caravan. The supply and the Caravan are all grounded to the same local earthing rod, so there is minimal potential voltage difference. So, if I'm standing outside the caravan and touch the metal body that may have an electrical fault - the voltage drop and hence the current flow will be minimal/reduced. The Caravan of course has a 30mA RCD and the main source supply has a 100mA slow RCD.
I love your lessons Sir!
Your videos is very good! (electrician, building manager in hungary)
Hi John great videos Would you consider doing a video on the '50v touch voltage' explaining what it is, how we use it, etc. Many thanks
Great video. Have to say your voice would be great in a podcast or radio!
yes - BBC
Super explanation thank you John
Always interesting to hear you sir.
The filling loop for as combi or system boiler is connected to the mains water supply, which is then of course connected to the entire internal heating pipework. Althought these filling loops are a rubber tube, this is covered with a metallic wire shield so presumably this also would require equipotential bonding.
Many thanks once again...I have returned...for clarity
Excellent. Why at 24:40 does JW explain that an RCD would NOT help in electric shock, if the person touches both the metal heater casing and the cold mains metal pipe? My misunderstanding i'm sure! The Live would be imbalanced against N current is flowing down through the person to CPC via Bonding conductor to MET. Can anyone explain please? The RCD should disconnect, quick enough to prevent death?
thank you for your effort
Do not assume pipes in floors (concrete) are touching the concrete giving an earth path. They will have a protective covering on them insulating them from concrete/cement.
Thanks John
Hi John, many thanks for the great helpful videos. Quick question though. After some kitchen renovations we now have a situation where the incoming water main pipe with the original main bonding clamp attached is now under the floor boards and the pipe then continues further along past the bonding clamp and branches off (A) left to our kitchen and comes up above the floor to our sink and (B) branches off right to feed upstairs to our bathroom. I am fully aware that the main bonding should not be past any branches and also should be above the floor for inspection. The other problem is that the copper pipes have been joined using tectite copper push fit fittings which I suspect would not provide sufficient bonding? I would be very grateful for any advice. Thank you again.
Good video thanks .
hi John would just like to thank you on all of your helpful videos and stress how useful they have been to me.
I just have a quick question that confuses me a bit and was wondering if you could possible clear it up.
using the scenario in your video. you say that if the boiler casing is live and you touch that (at the point before the fuse trips) you shouldn't get a shock, if you only touch the casing and nothing else. I was just wondering why this is as you are stood on earth which will have a different potential to the live casing (to me knowledge if this is wrong I apologise).
I hope this question makes sense and any help would be greatly appreciated.
My only understanding of this is that the bonded boiler would have a lower resistance to earth that a human so it would always use the bonded boiler as is path.
thank you for your time.
Interesting point about not needing to bond a water main where the incoming supply pipe is plastic.
I had wondered about this, but as all the houses here (built 1982, PME, plastic supply pipe) have a 6mm² bonding cable put in by the builders, and every house I've looked at where the CU has been changed or some other major work done the bonding has been re-run in 10mm² (usually in full view under the DPC across the front of the house) I've just wrestled 12m of cable through the house under the floor in preparation for a CU change.
It looks like I needn't have bothered.
Hi John
Great video
On tncs installation,where existing bonding ,water gas ,is at 6mm and db upgrade required to 17 edition,but is impossible to change the water or gas bonding to 10mm without damaging the finished laminated flooring.The tails and main earth can be upgraded to 25 and 16mm.Can we upgrade db without changing existing bonding from 6 to 10mm ?
the rule appears to be that you should never connect ground to neutral anywhere else than at the main panel. The reason for that (from countless individuals/websites online) is that once you do that, you would be a using a device's ground and neutral returns in parallel, and once the ground in a system is energized, this effectively energizes all other objects connected to ground in the system.
But given that ground and neutral are already connected together at the main panel, doesn't that do exactly what is meant to be prevented with this rule? Once you have conductors (ground/neutral wires) at equal potential somewhere in the system, how does connecting them elsewhere change their relative potential?
Hi JW. Really appreciate your videos. very well presented. The best I've seen.
Question:- I think by the lay out my supply is a TN-C-S system. Now the main earth from the incoming housing is only 10mm. Does the main protective equipotential bonding still require to be run in 10mm or would 6mm be ok ( which is what is already installed) or does the size need to be upped to 10mm
thanks
Mick
For TN-C-S the minimum size is 10mm, smaller sizes were allowed in the past.
For other systems it can be smaller if confirmed by calculation, but in most cases 10mm is fitted anyway.
Top Man Mr John
Hi john
Any chance of a video on calculating if bonding is required and if an existing cable is 6mm bonding is of a suitable size please
Hi John, excellent videos. I have a question about the bonding of the incoming water supply. From what I gleaned you are saying if its plastic pipe which typically it would be in all new builds, does that mean the water supply never needs to be bonded, even if the plastic pipe only enters the building to a length of a few feet before the connected metal stop tap and pipes? As a follow up, even if it is plastic, doesn't the water inside the plastic pipe essentially act as an extraneous conductive part, given it conducts fairly well?
phil taylor Bonding wouldn't be required if the water supply enters in plastic.
I'm an auto electrician but I have an interest in mains circuits. I have met a few guys who have said "I used to be an auto sparks,now I do mains,it's much easier" given that we are now dealing with networks,multiplexing, LIN,VAN,CAN,MOST,etc.I suppose there is that to it but only because we are dealing with electronics and software instead of physical switches, the principles are the same and many automotive electrical issues are physical wiring or more specifically connector based,so my reply is always "yes but 12 volt don't hurt",though with the increasing popularity of hybrids EVs etc.that's no longer technically true😗!What I see from my point of view of mains electricians is that the implementation of increasing amounts of automation and other technology going into buildings nowadays,that it is no longer the case of a couple of ring mains and lighting circuits and that the difference between both is becoming ever increasingly smaller and that's besides the ever changing electrical and building regulations yous guys have to follow,I had a pal rewire my workshop,six ramps,brake rollers,an outside,compressor shed,outside pressure washer socket etc. plus the usual sockets and lighting .both single and three phase and the rules and actual physical components needed against the original 1981 build was a real eye opener! . Anyway I have a question out of curiosity,Say for instance I have a fibreglass or porcelain bathroom fitting with metal taps fitted that are supplied by plastic pipework,in essence the taps are perfectly isolated but assuming that the plastic pipework will be connected to metal pipework at some point,(supply)and taking into account that the water its self is conductive does this then mean that the metal tap it's self should be earthed?or am I missing something😄
Hi John,
Recently contact NICEIC regarding a main equipotential bonding question. I asked weather a small external propane gas installation that supplies the property via a copper pipe through the wall would require bonding. They asked whether the gas pipework entered the ground outside at any point. I replied that it didn't and they said that in that case no bonding was required. It seems at odds with your explanation here . Do they have it wrong? Or have I misunderstood something?
Kind Regards
Sam
+starky497 The issue is whether the pipe is introducing a potential (earth potential in this case) into the building. If it was buried in the ground then it certainly would be and would require bonding.
If not in the ground then it may not introduce any potential so bonding not required.
All depends on exactly how it's installed - a small portable propane cylinder with a flexible connection would not be the same as a larger tank with fixed metallic piping.
Hai Mr.John,
Do you share a video about bridge rectifier for higher amps, include semiconductor fuse ,filter and snubber circuit for multi drive panels,if yes please include a catalogue also along with that??
you are the best
Hi John. Is it permissible to use structural steel as a main bonding conductor? The situation I’m referring to is a large industrial building where the services come in a long distance from the MET. Is a correctly sized bond from the MET to the steel work and then from the steel work to the services at the opposite end of the building acceptable?
John, I've a question to ask you regarding your video at 21:00 If the 'cold water tap' which has its pipe in the ground (for example), is touched at the same time that the hot water tap is touched (when the hot water boiler becomes live) then why does the recipient get a shock?What gives the earthing rod an impedance of about 50 ohms, but the cold water pipe an impedance approaching 0 ohms, when they're both in the ground? Sorry, it might be a silly question but I'd appreciate your time in helping me to clarify this. Thanks.
Hey JW, I have just discovered a water pipe in a bathroom that has been repaired with a plastic connector, is this dangerous and why? Also, what is the best way to remedy this? shall I just bridge the connector with earthing wire?
thank you
Thank you for the video, but I'm not clear on the case of mixed piping (plastic supply pipe burried in the ground, entering the building but further extended in the building in metal pipe network e.g. water). Graham Langley (below) understood from your video that in this case the metal parts need not be equipotential bonded as no potential is introduced (as the metal parts are not in connection with the ground becaus of the plastic supply)But Number 33 (below) said the water alone would account for a potential.Any ideas on who is wright? And if the piping would not hold water, but a non conducting fluid: would then equipotential bonding be (un)necessary?Thanks!
+klosty2 See www.plasticpipesgroup.com/media/1036/earthbonding.pdf
Hi john looking for a bit of info main water coming in is plastic but it's in a basement then runs up through the floor all installation is copper whats the best way to test to see if it needs to be bonded
I've read comments online saying that gas mains are now in polyethylene pipes. The cast iron pipes are being removed as they are corroding.
Also at 17:30 we look at a pipe such as a drain point for the heating system. I'd say that a pipe doesn't introduce an earth potential just because it emerges from the wall, outside the building. Doesn't it need to be in contact with the mass of Earth to do that?
PE pipework has certainly been fitted for at least the last 30 years in gas distribution mains and services (as indeed they have in water distribution). However many of these pipes are either laid inside existing iron pipework or in some cases steel pipes are laid (higher pressures are typical for steel pipework). NB as JW says ALL gas pipework from the ECV is metallic, and any above ground entry will also be metallic. Below ground entries have not been fitted for a long time now and all are metallic.
I didn't know that many PE pipes are laid in the old metallic pipes. I'm not sure what an ECV is, and I got confused at the last paragraph about entry points above and below ground. Wouldn't it be useful to eliminate any metallic parts just before entry into a building? We'd no longer need to bother with main equipotential bonding.
The mains water may enter the building via a plastic pipe which is non-conducting, but the pipe contains water which, unless the water supply is distilled water (very rare), is conductive. So taps and steel sinks etc. will still be at ground potential.
+number 33 Not true: www.plasticpipesgroup.com/media/1036/earthbonding.pdf
+klosty2 I stand connected . . .er corrected
Thank you Sir. Question: If the metal pipes (water or gas or soils) comes from the ground and enters the building, the pipes are already earthed and thus at "zero" potential via entry from ground. Any stray currents would flow naturally along the pipes into the ground. Why we need to clamp a separate cable onto the pipes on consumer side to connect to the earthing system of the building, both pipes and cables are grounded at "zero" potential? Greatful for advise.
The purpose of bonding is to keep the parts at the same voltage when a fault occurs.
Without it, an appliance casing could become live, and you would then have 230 volts between that and a pipe. Connecting them together with bonding keeps the pipe and appliance casing at or near the same voltage to significantly reduce the shock risk.
MR John Ward, would the MCB not trip before making the extraneous conductive parts LIVE though?
JW in a 3 phase commercial building is it acceptable to connect a Main Protective Bonding Conductor to a sub distribution board in the building as opposed to the MET if the supply cable to that sub board is adequately sized?
Yes.
Do you have one about banjo bonding in panels because i deal with a lot of Bs or Middle eastern wiring. Plus i also work along side British electricial inspectors and can you help
John do you have a video on testing a TT system bonded earth
In an apartment on the 3rd floor. At some point, the feeder water pipe was replaced with PEX. There is still a bonding conductor connected to the cold water pipe under the kitchen sink.
1. Shouldn't this bond be removed?
I heard that in very old installations, maybe the water pipe was used as the main building/apartment ground?
My concern is, are we replying on the earthed water pipes of the other apartments and what happens as they corrode and also get replaced with PEX?
2. How do I check whether there is a low impedence building earth ground, in addition to the utility earth ground, and not just earth bonding through the water pipes of other apartments?
22:29 looks like the water pipe is a more effective ground that the electrode itself!
It quite often is, large lengths of metal piping in the ground is far better than a single rod.
However metal pipes can be replaced with plastic ones, so water pipes can't be used as the means of earthing.
So if I understand correctly, bonding is the most essential in TT systems ( because of the large impedance od earthning). In TN-S and TN-C-S systems, we have very low earthning impedance, thus the circuit breakers will pop in no time, so it will by highly unlikely for a person to hold the pipes and electrical equipment in the same time when fault occurs. Is that correct ?
TheRodionRaskolnikow A high earth impedance results in higher voltages on exposed conductive parts when there is a L-E fault.
Disconnection times will be similar regardless of the earthing arrangement, although it will usually be an RCD disconnecting for a TT supply rather than a fuse or circuit breaker.
***** Right, thanks for answer I am new in electrical instalations. So in TN-C-S and TN-S, in case od L-E fault, voltage drop across exposed conductive parts and ground will be very low, so risk of getting electric schock is also very low.
I have one more question, imagine TN-S system, without RCD, only with 16A fuse and earthning resistance of 1 ohm. If we short L and PE together. Will we get 230 amps for a short period of time ? or at least 50 amps before fuse will pop.
TheRodionRaskolnikow Yes, with 230V and 1 ohm, the current would in theory be 230A until the fuse failed.
In reality, it is more complex, since while the fault current flows, the fuse element will heat up causing it's resistance to increase, reducing the current.
***** Right, resistivity of metal conductor ( for ex. cooper ) rises quite quickly, when the temperature is rising, i didin't thought of that. Thanks for your time and knowledge :)
What if there is a section of plastic pipe joining two copper pipes? The first copper pipe is bonded as described in your video but the second copper pipe is a shower feed (behind the tiles of a shower enclosure) and the plastic section has been installed for ease of joining the two copper pipes. It would be very difficult to install an earth wire to the shower feed copper pipe. This is not an electric shower but fed from a combi boiler - so two pipes (hot and cold) in this situation.
If there is a plastic insulating section, the rest of the copper pipe beyond the plastic section probably isn't an extraneous conductive part (this can be confirmed by testing) and therefore would not require bonding.
An air conditioning unit with external compressor would have extraneous copper pipes running to the fan coil unit in the building.
Surely bonding these pipes is superfluous as they are grounded via the CPC of the supply?
Bonding probably not required, as they won't be introducing any potential from outside - they typically won't be buried underground.
Hi John, can you please explain why at time 22:20 the equipment would be at the mains potential of 240v? Thank you
Becaus the hearing element has shorted out and the live wire has touched the outer casing of the device
at 20:00 why would the fuse blow? I thought the RCD would trip because some current is flowing through the CPC?
In my house, I have water storage and a water pump for the house that pumps when a valve/tab is opened because of pressure drop. I have the feeling that something electric wise is wrong with the pump and in a hort distance from the pump, I have a metal valve that has static on it.. All is connected by pvc pipe. Bonding might be difficult. Any suggetion?
I have come across a job. The CU is new with RCD, PIR testing is done. Everything is fine, but no bonding! Water stop cock is in the toilet and it is too difficult to run CPC unless take off the whole toilet system. The gas meter is outside and running the Y/G cable inside the house makes it ugly as the floor is nice tiles. The customer is not happy doing that. I wonder what code it would be? As if it was code 3 it would pass?
Thanks John
Missing main bonding is C2, and the report would therefore state unsatisfactory.
@@jwflame appreciated John.
Hi John. how can I do bonding if the gas meter is outside the house. If a cable is run through the house it will mess up with the whole house as it look ugly. ny suggestions please.
Thanks
+Hamid Bazmi Bonding connection is made where the gas pipe enters the building, does not have to be at the gas meter.
Cables can be run externally, or concealed behind coving, under floors, through the roof space and down the external walls, and many other possibilities.
Many thanks John. Looking forward to more videos. If possible some videos on real jobs. Something about kitchen ring, saw running for loft with a new consumer unit, and perhaps 3 phase on a medium commercial premises like dry cleaning.
Thanks again.
My house doesn't appear to have any bonding of extraneous conductive parts. I have metal gas and water pipes entering the house with no sign of any electrical connection to them. The main earth point next to the meter is connected to the sheath of the incoming cable and only has one wire which goes via an earth leakage circuit breaker to the fuse box. Is this a recent requirement, ie within the last 50 years, or does it not apply to a TN-S system where it would appear to be unnecessary? Note I said fuse box, none of this newfangled consumer unit rubbish.
+number 33 It applies to TN-S, TN-C-S and TT, and has been a requirement since at least 1966.
+John Ward Thanks John, my house was built in 1959 which probably explains why there's no bonding. I seem to remember that I promised to give you the old Chilton ELCB for your collection when I replaced it but when I measured the actual leakage current flowing in the coil it was varying up to about 50mA so I decided to delay replacing it until I have tracked down the source of the leakage. I'll get around to it one day, maybe.
Hi john on a consumer unit change if the bonding is 6mm and shows no signs of damage is it ok to leave in or will it need upgrading to 10mm
Yes for a TN-S or TT supply. Not for TN-C-S, which requires 10mm² minimum.
@@jwflame ok John thank you
I don't get why my plastic mains water pipe is bonded and the entrance to the property?
It never made any sense to me.
Its the original pipework from the 70's - 80's and is imperial sizing on the plastic and metric on the copper.
If incoming water main is plastic (blue pipe) but turns into copper pipe at the Installation side does it still require bonding? Cheers
Probably not - but it would if those copper pipes go into a concrete floor or similar within the installation.
If the main inlet gas pipe is bonded does the gas pipe to the hob also have to bee bonded? Thanks
No. Bonding at the entry to the property only.
Tanks
Can I make bonding connection inside the flat instead of 600mm from the gas meter outside on the soil . The flat is on the third floor , and will require 25 meter long bonding conductor
Yes, bonding is connected where the metallic pipes enter the property, which isn't always where the gas meter is.
@@jwflame cheers John 👍
***** could you make a video explaining the TT,TN & IT systems? I find it hard to understand.
Rohit Lakshmanan This should cover most of it: czcams.com/video/AWxeb2MI37c/video.html
All right. Thank you! :)
1. Can the protective bonding bar be inside of the distribution panel casing? Is it possible and allowed? What I mean is if it can be the PE connections bar inside the electrical panel casing, because I cant see any other electrical bonding bar inside of my house.
2. What does the connecting of the sheath of TV aerial cable look like in real life? Does anyone ever does it?
Yes, the earth / bonding bar can be inside the panel or consumer unit.
For TV aerials, things like this are used: www.blake-uk.com/equipotential-bonding-bars/215-8-way-earth-bonding-bar-proception.html although normally only done for larger systems with multiple outlets.
Hi john we fit a lot of plastic sure stops just after the stop tap, does this in any way effect the earthing system and therefor should the sure stop be cross bonded?
No, but the main bonding should be connected on the house side of the SureStop.
Main bonding within flats? Is the bonding required within each flat?Great vid thankyou
Usually yes - it's designed as each flat being it's own equipotential zone with it's own bonding and earth connections.
In theory it could be done for the building as a whole, but that would also require proper controls over all alterations to the system, something which is not possible where each flat is owned by different people.
A plastic gas main coming into your house is _zero?_ No.
Internal installation pipes are *not* guaranteed to be earthed. If installed properly the pipes will not touch masonry. If he gas meter is removed and main pipe capped, with the earth attached to the internal pipe on the outlet side of the gas meter, there is a good probability it will not be earthed.
Good
Is it 6mm earth bonding good enough for periodic report John
Depends on the type of supply. For TN-C-S minimum of 10mm² required. For TN-S or TT smaller sizes may be permitted.
Its TNS thanks for your help mate
Hi John My heating system is fuel oil l presume this requires bonding , can you confer
Only if the incoming oil pipe is exposed bare metal. Many are plastic coated.
If it is bare metal than bonding may be required - a resistance test between the metal pipe and earth will confirm, low resistance = bonding required.
You will need a clamp designed for small diameter pipes, the usual BS951 type are not suitable for the small 10mm size normally used for oil boilers.
Thank you
John....great videos for an enthusiastic amateur but I'm confused. At about 20 mins you describe a fault occurring and the casing developing a "fairly large voltage". You then say that as long as "that's the only thing in the room" and you touch it you won't get a shock because you're "not connected to anything else". I don't understand that. Surely if you are standing on the ground and touch a "live exposed conductive part" you will get a shock. Is it something to do with a TT system in your example?
You probably would get a shock, that comment was more about the dangerous situation of holding two conductive items of different potential rather than one item and the floor/wall or whatever.
I thought the Green Text in the mini thumbnail said "Man Bonding"
👍👍👍👍👍
Iv got 260 ohms on my tt at home
Ben
HELLO MY FRIEND TU NE REPOND JAMAIS AUX COMMENTAIRES
Hi John great video keep it up, I have a question regarding the thickness of the earth cable for the gas and water pipe ? Is it always 10mm2 or can it be higher , just want to know what is the minimum requirement according to regulations?
For TN-C-S the minimum is 10mm², it can be smaller for TN-S and TT, although it's common to find it as 10mm on those as well.
It can be larger, and is required to be larger on some installations.
Thank you John appreciate it.