A bit of bondage!

[aptsys]

troll View media item 32946

 

[bernardgreen]

oh dear, oh dear, Bernard (or is that AKA cocky?) has just mentioned the C-word.

Hi Mike

Sadly C for Compromise has to be included when creating regulations that are required to do the impossible which is to fit all situations.

And as a result safety IS compromised in some situations where force fitting the regulations required some bending of things too far.

There are many situations, like metal windows and metal door frames with switches fitted in domestic situations, which are so rare they rate very low for consideration when the compromises are made during the writing of regualtions. But they do occur and so it is necesssary to be aware and prepared for them. An electrician cannot say that if the regulations do not specifically mention an item then it can be ignored when designing the system. (are metal framed windows mentioned ? I do not know ).

 

[mikhailfaradayski]

oh dear, oh dear, Bernard (or is that AKA cocky?) has just mentioned the C-word.

Hi Mike

Sadly C for Compromise has to be included when creating regulations that are required to do the impossible which is to fit all situations.

HI Bernard,
Sorry, i mean't C for common, as in common sense. In this day and age of red tape, regulation and a blame culture, it seems as common sense has no place here anymore

And as a result safety IS compromised in some situations where force fitting the regulations required some bending of things too far.

There are many situations, like metal windows and metal door frames with switches fitted in domestic situations, which are so rare they rate very low for consideration when the compromises are made during the writing of regualtions. But they do occur and so it is necesssary to be aware and prepared for them. An electrician cannot say that if the regulations do not specifically mention an item then it can be ignored when designing the system. (are metal framed windows mentioned ? I do not know ).

 

[bernardgreen]

Hi Mike

I did for a moment think that you had meant Common sense but as we know that is now a banned skill and best not to talk about it in case some DIYer starts using it.

 

[mikhailfaradayski]

sssshhhhhh, don't mention it again and I think we'll be ok.

 

[bernardgreen]

Perhaps if we spell it cents then we can say it is part of the Euro

 

[Spark123]

My idea, that I have put in writing to the BSI, is to ask the manufacturing companies of modern aluminium double glazing to produce windows and doors, which have handles that are electrically speaking isolated from the frames. This should not be too difficult for them to achieve with the use of 'nylon' spacers and washers.
Hopefully this will relieve us of the burden of having to bond aluminium double glazing in the future.

You're almost a week late

 

[ricicle]

You're almost a week late

 

[Buzx1313]

time to stop now... getting boring

 

[securespark]

2. As I sometimes take the pen home (27 miles) what thickness should the bonding wire be?

As long as the total conductor resistance is sub 0.05 Ohms, you're OK.

150mm2 should do it.

EDIT:

I'm sorry, I've made a classic schoolboy error and not looked at the total length of the conductor.

I think it may need to be bigger, but don't worry. Just go with the biggest and you can't go wrong.

How much is 1Kmm2 single core BS6346 anyhow? The price just may be a little prohibitive.

 

[bernardgreen]

time to stop now... getting boring

While I accept the discussion is probably boring and confusing for the average DIYer I find the discussions about the differences between earthing. bonding and true ground are fascinating.

Seriously the claim that equipotentially bonding a pipe to an earth terminal at the incoming supply cannot be refered to as earthing the pipe is contrary to common sense. Of course the "earth" is often not true ground and a bonded pipe can be several volts from true ground potential.

In humourous mode, how long before any conductive ground around a house will have to be equi-potentially bonded to the earth terminal. ( mild shocks from gas meters connected to equi-potentially bonded internal pipe work ) That wire will be hard to describe. In one direction it will be an earth wire and in the other direction it will be an equi-potential bonding wire. Or will the wet grass and topsoil need to be double insulated from the ground underneath it to remove the "earth" function from the wire.

 

[david911cockburn]

Hi All,
Let's look at the past and EEBADS without the benefit of the RCD.
Now nobody is claiming that EEBADS is fool proof without the invention of the RCD. For example in a circuit protected only by a fuse or circuit breaker, if your client (or you) should come into direct contact with a circuit conductor whilst simultaneously being in contact with an earthed conductor, a large amount of current will be able to flow accross the body and this is presumably the reason that some members of the industry did not agree with EEBADS as a safer principle.
With the invention of the current operated RCD, or more especially the 'split load' distribution board which removed the problems of nuisance tripping, the problem of simultaneous contact with a circuit conductor in one hand and an earthed conductor in the other ceases to be a problem as the RCD will automatically disconnect the circuit when 30mA of current flows.
Therefore if we use EEBADS and a 'split load' dist. board with the lighting circuits on one side and all of the other circuits protected by the RCD on the other, we can say that our clients are as well protected as they need to be especially from their trailing flexes and extension leads. But now with the invention of the RCBO, which we can now add to the 'split load' board to protect the lighting circuits. We can also take the opportunity to protect ourselves from simultaneous contact, with the circuit conductor of a lighting circuit in one hand and an earthed conductor in the other!
This is called 'progress'.

 

[holmslaw]

Hi Dave, how's your knob?

 

[Robgers]

Holmslaw you have just made my day

 

[david911cockburn]

Hi Bernard,
You seem to be worrying about 'Indirect contact', or the human body proving a second 'parallel' path to earth.

I believe that earlier on in this thread I mentioned that the definition of 'indirect contact' had mistakenly been taken straight from the 15th Edition without being updated, it read;
Indirect contact - Contact of persons or livestock with exposed-conductive-parts which have become live under fault conditions.
Which is incorrect!
This definition should have been updated to read something like;
Indirect contact - Contact of persons or livestock with earthed conductive parts (in the case of earth leakage current).
And;
Indirect contact under fault conditions - Contact of persons or livestock with earthed conductive parts (in the case of earth fault current).

In either case you are correct that if the recipient is in good contact with earth they will recieve a nasty 'nip' (ask any plumber), but because they are only providing a second parallel path to earth the amount of current that can flow will not exceed the recognised 'let go' value (which is somewhere in the region of 5mA if my memory serves me correctly), therefore the shock should not be life threatening.

Holeslaw - Grow up son.