Main bondage

[telectrix]

IMO, the resistance measured ( of a main bonding conductor ) should tally with the mohms/m ( in BS7671 and 0SG as 0.0018ohms/m for 10mm) multiplied by the length in metres. so a lentgth of 27.7m should read 0.05ohms.

 

[Gavin A]

Not at all, I have been trying to educate the poster on the question of the max value of the main bonding conductor, not sorting out his high value, I thought others had pointed him in the right direction regards, joints, reduced cable size hidden and re-joined behind walls or somewhere. As someone said with the reading he was getting it would have to be a very long cable indeed. If he used a wandering lead method he could of obtained an estimate of the length etc................................But THERE IS NO MAX value of 0.05ohms for the main bonding conductor the his measurement has to be below. Reread his question ................. So no not a cop out a FACT

well it's a cop out from the subsequent questions.

If the maximum value is not 0.05ohms as you repeatedly state, what in your opinion should the maximum resistance value of a main bonding connector be?

In the absence of any sensible answer to this question, I reckon I'll stick with the guidance given such as the guidance below, even if it is just a ball park / rule of thumb figure.

The resistance between any extraneous conductive part and the main earthing terminal should he 0.05 Ohms or less; all supplementary bonds are also required to have the same resistance.

http://www.tlc-direct.co.uk/Book/8.4.1.htm
ps I know that relates to 16th edition, but did anything change in terms of main earth bonding between 16-17th that would affect this? and yes, I'm aware it's also just a guide and sparks are under no obligation to follow it etc but IMO you'd need a decent logical reason why not, and this thread hasn't supplied any IMO.

 

[ezzzekiel]

Providing pipework is effectively bonded
Then its resistance will depend on the length but would ensure a dangerous potential will not occur between parts

 

[KAS1]

Where is TLC DIRECT quoting from I bet if you look closely it's that "Extracted from The Electricians Guide Fifth Edition
by John Whitfield" I think he's been know to make mistakes

well it's a cop out from the subsequent questions.

If the maximum value is not 0.05ohms as you repeatedly state, what in your opinion should the maximum resistance value of a main bonding connector be?

In the absence of any sensible answer to this question, I reckon I'll stick with the guidance given such as the guidance below, even if it is just a ball park / rule of thumb figure.



http://www.tlc-direct.co.uk/Book/8.4.1.htm
ps I know that relates to 16th edition, but did anything change in terms of main earth bonding between 16-17th that would affect this? and yes, I'm aware it's also just a guide and sparks are under no obligation to follow it etc but IMO you'd need a decent logical reason why not, and this thread hasn't supplied any IMO.

 

[Elmer BeFuddled]

is it just me? i thought we cleared all this ages ago?

I'm confusticated!

 

[Gavin A]

Where is TLC DIRECT quoting from I bet if you look closely it's that "Extracted from The Electricians Guide Fifth Edition
by John Whitfield" I think he's been know to make mistakes

that was just one example.

I note you're still avoiding directly answering the question posed.

what in your opinion should the maximum resistance value of a main bonding connector be?

 

[Des 56]

I'm confusticated!

Shall we restart this thread again

 

[Elmer BeFuddled]

Shall we restart this thread again

Please! I'll start.
Marmite should be spread no thicker than 0.05mm on thin sliced toast according to the EBF 1958:2013 Amd 55.

Discuss.

 

[Des 56]

Please! I'll start.
Marmite should be spread no thicker than 0.05mm on thin sliced toast according to the EBF 1958:2013 Amd 55.

Discuss.

But that is only guidance,the thickness of the Marmite will not affect the taste

 

[KAS1]

It all depends on the length and size of the cable a bit basic really, how can you expect anyone to come up with a max value without knowing a length and size you can't expect me to mind read, Now can you grasp "the max value of any cable/core" it's easy maths lol

that was just one example.

I note you're still avoiding directly answering the question posed.

what in your opinion should the maximum resistance value of a main bonding connector be?

- - - Updated - - -

Can't stand marmite lol

 

[Geoffsd]

THIS IS ONE OF THE MOST FAILED QUESTIONS IN TEST AND INSPECTION EXAMS when the question has been asked state the maximum value of resistance of a main protective bonding conductor...................I REST MY CASE END OF FINISH

I presume that students are advised and probably instructed to read GN3 in which case that would very reasonably be viewed as a trick question.

Furthermore, why would such a question be asked if there is no maximum resistance value?

Getting the question wrong would only result in an installation being 'safer'?

 

[Chr!s]

The figure 0.05 is just a means of confirming a connection say between a RSJ joint, simple, that's lt.

Main Bonding lust needs to be sized correctly, the length Is irrelevant.

The op, he needs to ensure his test equipment is calibrated and correctly connected.

The resistance needs to relate to the length and csa.

If it doesn't he needs to identify why and remedy.

 

[netblindpaul]

I can't believe that this is still going on.
A competent electrician should KNOW this without asking.

 

[Silly Sausage]

The figure 0.05 is just a means of confirming a connection say between a RSJ joint, simple, that's lt.

Main Bonding lust (haha...back to the thread title) needs to be sized correctly, the length Is irrelevant.

The op, he needs to ensure his test equipment is calibrated and correctly connected.

The resistance needs to relate to the length and csa.

If it doesn't he needs to identify why and remedy.

Exactly!
If the length is irrelevant and some like to say there is no upper resistance specified, you may as well use 1mm[SUP]2[/SUP].

So therefore, the resistance of the cable must have some significance.

 

[Guest55]

Exactly!
If the length is irrelevant and some like to say there is no upper resistance specified, you may as well use 1mm[SUP]2[/SUP].

So therefore, the resistance of the cable must have some significance.

well thats not quite right is it ?
a minimum sized bond conductor is specified , but no upper resistance value needs to be complied with for that conductor if its the correct csa.

 

[Chr!s]

Exactly!
If the length is irrelevant and some like to say there is no upper resistance specified, you may as well use 1mm[SUP]2[/SUP].

So therefore, the resistance of the cable must have some significance.

Archy, 1mm would be fine, when calculating touch voltage you assume little or no current in the conductor.

The min 6mm is for mechanical strength.

 

[Chr!s]

Archy, 1mm would be fine, when calculating touch voltage you assume little or no current in the conductor.

The min 6mm is for mechanical strength.

Forgot to say, Bar pme broken pen where current may flow, this is dealt with within the reg, but still only correct size required.

 

[onions1066]

I know how to put this one to bed........................ Who thinks we should use TT system to an outhouse?

 

[Silly Sausage]

well thats not quite right is it ?
a minimum sized bond conductor is specified , but no upper resistance value needs to be complied with for that conductor if its the correct csa.

That's what the regs say, half the Main E C, and no resistance value specified.
But why?


edit...


I'm sure I vaguely remember when I did my 2391 10 years ago, they said, 'If you're meter reads zero when testing bonding conductors, write down 0.01!

 

[Guest55]

That's what the regs say, half the Main E C, and no resistance value specified.
But why?

if bs7671 gave a maximum resistance value for any given bond conductor it would restrict its length.
no resistance limit = unlimited length.