A bit of bondage!

[david911cockburn]

Ricey,

You are giving the impression to the people who have respected your opinions in the past that you are in reality little more than an irresponsible, ignorant, irritating little boy!
Is that really what you want people to think of you?

 

[bernardgreen]

no longer referred to because the IET and others are now trying to cover up the mistakes they have made.

In my opinion they were not mistakes but a clumsy attempt to rationalise the situation that has developed over the years.

A compromise between [1] "earthing" to provide an adequate route for fault currents such that they are large enough to ensure dis-connect devices will operate and [2] "bonding" to ensure that in the event of a fault all metal parts that can be touched by a person will be at the same potential, the equipotential bonding.

It was complicated because the "earth" conductor in a TT system with voltage operate circuit breaker has to be insulated from earth otherwise the circuit breaker's operating coil was effectively bypassed and could not work when needed.

The guidelines are still compromised in that the equipotential bonding is almost always connected to the earth CPC in things like boilers and immersion heaters, ( electrical supply CPC to pipe work, then pipe work to equipotential bonding around the building ).

The situation is then complicated by the fact that in all but TT supplies the CPC is not connected to earth but to the neutral of the incoming supply. Which unless there is a ground rod for the neutral right at the point it enters the property will never be true earth ( ground ) potential when there is any current flowing in the neutral. ( voltage drop along the neutral ) If the only "bond" of the neutral to ground is at the substation then the potential of the "earthed" CPC in the building can be several volts different to true ground. That is not a problem inside the building as equipotential bonding keeps every at the same potential even though it is not necessarily true ground potential.

The problems come when that CPC is exported to outside the building. Gas meters and external water taps supplied by copper pipe are at the potential of the CPC and therefor may be several volts different from true ground. In a network fault condition they could be 230 volts above true ground while the buildin appears to be wth out any power. ( such as a failed neutral ). Everything in the building that is earthed or equipotentially bonded will be at the potential of the live conductor. In many situations the RCDs in the building are likely to operate but any circuit that is not RCD protected and has equipment switch on will provide a circuit through the equipment for live potential to reach the neutral and hence CPC conductors. The equipment will not work so appears to be without power and safe.

Given that set of conflicting requirements about earthing, equipotential bonding and CPC's derived from the Neutral of the supply is it any wonder the "regulations" and guidelines are at best a compromise and at worst a flawed attempt to minimise risks ?

 

[skenk]

FWIW I think your postings are tantamount to trolling too, mr cockburn. RF Ligthing, Spark123, dingbat, Ricicle and others have gained my respect over years of reading this forum. Your postings and from what I have read of your book on amazon have the opposite effect.

Your muddled use of grammar and terminology lends nothing to the discussion on earthing and bonding, one could only feel sympathy for anyone seeking knowledge on the subject who was unfortunate to come across your 'book'.

You seem to think that all your proclamations and the content of your wafer thin publication are correct, while the respected opinion of many, the entire IET, the Amazon book-buying public and, it would seem, anyone with a bit of genuine knowledge of the subject is incorrect. Don't you think that's just a little odd?

Have you ever admitted you were wrong about anything? Or is it just because you are involved in a desperate attempt to save any reputation you had that you cannot 'see the wood for the trees' in this case?

 

[westie101]

Just read this during lunch - wish I hadn't

The various bonding requirements especially for TN-C-S think Faraday Cage, especially if the neutral/earth is lost.

Oh and touching live conductors, been there not got a shock (our guys do it day in day out)

 

[david911cockburn]

Hi Guys,
Nice to hear some genuine debate.
Westie,
For the touching an energised circuit conductor experiment you need to be upstairs with your boots off, standing on floorboards.
If you haven't had a nasty shock up to now, it won't be long before you find one!

The one thing that you all seem to be over-looking is the fact that the earthing of all conductors (other than circuit conductors) is the Law!
This means that there is little need for any of us to think too much about it, we must obey the Law or if and when 'it' hits the fan, we will be accused of negligence and some pencil necked Lawyer will convict us of Manslaughter as a result.

The obvious way to prevent charges of 'manslaughter' from happening in the long term is simply to return the Wiring Regs. to a 21st Century equivalent of the 1991 version without delay, having done this and shown that we are doing all that is reasonable practicable to rectify the situation we currently find ourselves in, any deaths or injuries caused by current installations will have to be put down to 'misadventure' (and a slap on the wrist rather than 14 years inside).
All this will cost is a little pride!...; and there will be stacks of work for all of us as nobody wants an Electrical Installation that fails to comply with the British Standard.

 

[holmslaw]

Is there anything you're good at?

So as long as I'm upstairs with me boots on, I can't get a shock, thats my bedroom slippers binned. Do you reckon it would be safe to take off me boots before getting in the bath or going to bed?

Lawyers do not convict anybody, that's what judges and juries do. Have you perchance written a handy guide to the law?

 

[Robgers]

He fried with his boots on

 

[IJWS15]

Mr Cockburn

From your posts:

Hi Guys,
The one thing that you all seem to be over-looking is the fact that the earthing of all conductors (other than circuit conductors) is the Law!

and from earlier

Conductor - means a conductor of electrical energy.

I have in my hand a give away pen provided by one of those pencil necked firms of lawyers carefully emblazoned with their logo. It has a metallic clip which I believe falls under the definition of a "Conductor" since I can use it with a bettery to light a torch bulb.

Are you saying it should be bonded (presumably to my desk - also partly metallic)? If so:
1. how do I avoid people tripping over the trailing wire when I go to a meeting with the pen, as I often do?
2. As I sometimes take the pen home (27 miles) what thickness should the bonding wire be?
3. Why is the pen clip any less dangerous when I am using the clip to light a torch bulb when, according to your posts, it does not need bonding as it is then a "circuit conductor".

Could you please explain.

Typo corrected

 

[westie101]

For the touching an energised circuit conductor experiment you need to be upstairs with your boots off, standing on floorboards

Hmm let me see, touching a live terminal whilst standing on dry wood which is a pretty good insulator - can't see a problem. I'll try it next time I take a carpet up!

As for touching live conductors generally, as I stated where I work we have guys do that every day, sometimes up to 11kV.

 

[david911cockburn]

Westie,
For christ sake there are young impressionable minds reading this!
I have already spoken about high voltage systems, EEBADS will obviously not work on 11Kv other than for over-current protection at the time of a fault to earth.
When you get home, if you intend to prove to yourself that an RCD will not replace supplementary bonding, go upstairs lift up the carpet, take off your boots, loosen the front off of a socket outlet, stick an un-insulated screwdriver in to the L terminal and touch the back of your finger onto the shank of the screwdriver. The result will be a nasty shock even though you are upstairs and apparently not in contact with earth! But because you will not be in good contact with earth the RCD will not automatically disconnect the circuit (ramp test the RCD before and after).

Dear Sir who's name I have forgotten,
A pen in this case is a conductor that is true but it is not fixed or otherwise immovable, in common with a household flexible circuit conductor it is also too small to be gripped by the human hand (it can simply be pulled through or out of the fingers) therefore it is not reasonable forseeable that it will present any added danger if it were somehow to become hazardous live. Unlike a radiator, metal sink, bath or any other piece of isolated copper pipework.

 

[ricicle]

TROLL

 

[david911cockburn]

Keep your hair on Ricey, I'm still thinking about it.

 

[westie101]

But because you will not be in good contact with earth the RCD will not automatically disconnect the circuit

Oh there is no doubt that the RCD will fail to operate!

But the current flow through me will no doubt be below a level that will have a harmful effect on me, and probably below a level that I will detect.

 

[david911cockburn]

Hi Westie,

I would be nice if your assumption was correct but unfortunately I know from experience that it isn't!

There is a much less painful way to prove the point, get yourself a 'neon screwdriver'. If your assumption was true a neon screwdriver wouldn't be able to work, but we all know that they do.

 

[westie101]

Actually I think to avoid household disruption I'll get a Megger and get a value for the insulation resistance of the wooden floor to earth, ohms law should then give a reasonable value of the expected current flow. (of course it is a DC test and will give a value of resistance as a result, whereas it should be an AC test to give the result as an impedance. But within experimental error the result will be valid enough)

I'll even let you choose the test voltage, 500V, 1000V, 2500V or 5000V (if you want higher I'll pop into work and borrow a 50,000V test set