Earthing & Bonding - Part 2 : Main Protective Equipotential Bonding

Part 2 looks at main protective equipotential bonding, why it is needed, the size of conductors to use and what needs to be connected.

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[brianlopez]

NO daft intro or music, just straight clear facts. Fantastic.

[Backacheme]

I congratulate you Mr Ward on (yet) another first rate presentation made with wisdom, clarity and humour, thank you!

[danieleuboldi]

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

[tonybrock]

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.

[Graham_Langley]

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.

[movaxh]

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.

[ManUned]

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.

[loghead]

You sir have just earned a new subscriber.. Fantastic info thank you

[peterjones]

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.

[martinporter]

JW, Thanks for the vids. You are one of the best tutors on Youtube. 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.

[timothymack]

Thanks John for another concise and informative video. Easily the best resources available for revision.

[Danxr-kj]

No supply in Separate. Earth is combined with neutral at the end of a cable run ie Potend, at the LV fuse board in the substation and via the street furniture outside.

[davidw]

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 :)

[abdullahalahmadi]

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?

[johnburns]

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.

[RaxTubeYou]

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?

[obviouslytwou]

JW is my best channel. Because his is smart and English

[areyouundoingthatorwhat]

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😄

[robinmitchell]

Great video. Have to say your voice would be great in a podcast or radio!

[westinthewest]

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?