Main bondage

ultinator · Feb 8, 2013

Does main bonding in every circumstance always need to be under 0.05. main bonding in a house where the main water was moved has 10mm cable but resistance of 0.25 ohms!!>>

Guest55 · Feb 10, 2013

Geoffsd said:
Within reason, the resistance will obviously be very low.

and its the interpretation of this particular statement that is the cause of opposing views.
the fact that bs7671 doesnt expand on it leaves everyone to draw their own conclusions.
and that is probably the most satifactory end to this debate we're gonna get.

KAS1 · Feb 10, 2013

0.05 ohms was mentioned in Op and it was asked "has the maximum value of the main bonding conductor got be below that figure of 0.05ohms" (it's so long ago I think that's what was asked) and all the way through this post I have said NO it doesn't at all. As long as the main bonding conductor is selected with BS7671 in mind 0.05 ohms does not even need to be considered.

Geoffsd · Feb 10, 2013

So - could it be as was raised earlier?

R (of Main bonding conductor) ≤ 50 (or whatever value you deem 'safe') / Ia (of the main fuse)

Gavin A · Feb 10, 2013

KAS1 said:
0.05 ohms was mentioned in Op and it was asked "has the maximum value of the main bonding conductor got be below that figure of 0.05ohms" (it's so long ago I think that's what was asked) and all the way through this post I have said NO it doesn't at all. As long as the main bonding conductor is selected with BS7671 in mind 0.05 ohms does not even need to be considered.

that's a cop out answer.

the bonding conductor was already in place, and was being tested to confirm whether it actually did comply being as it wasn't visible for it's entire length so the integrity of the conductor couldn't be verified by visual inspection.

Given that this test has been conducted, what in your opinion should be the maximum acceptable resistance reading for that bonding conductor?

KAS1 · Feb 10, 2013

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

Gavin A said:
that's a cop out answer.

the bonding conductor was already in place, and was being tested to confirm whether it actually did comply being as it wasn't visible for it's entire length so the integrity of the conductor couldn't be verified by visual inspection.

Given that this test has been conducted, what in your opinion should be the maximum acceptable resistance reading for that bonding conductor?

telectrix · Feb 10, 2013

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 · Feb 10, 2013

KAS1 said:
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 · Feb 10, 2013

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 · Feb 10, 2013

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

Gavin A said:
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 · Feb 10, 2013

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

I'm confusticated!

Gavin A · Feb 10, 2013

KAS1 said:
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 · Feb 10, 2013

Elmer BeFuddled said:
I'm confusticated!

Shall we restart this thread again

Elmer BeFuddled · Feb 10, 2013

Des 56 said:
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 · Feb 10, 2013

Elmer BeFuddled said:
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 · Feb 10, 2013

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

Gavin A said:
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