Max continuity reading for bonding

[Questforknowledge]

Good evening

I was always taught the gas and water bonds should have a continuity ideally with a maximum of 0.05 ohms, is this a exact maximum or a rule of thumb and if it was higher than this what coding would we give it? I had a look through the codebreakers booklet but could not bit see an answer

Cheers
HARRY

 

[davesparks]

Did you ever look it up in the regulations or guidance notes?

There is no maximum resistance specified for bonding, just a required CSA. You should be able to work out what a reasonable resistance would be by estimating the length of an installed binding conductor.

0.05 is the suggested maximum resistance of the connection of an earth clamp to a pipe or other means of making a bonding connection.

 

[DPG]

Common misconception this one. Not sure how people think there could be such a maximum figure when the length of run could be absolutely anything.

 

[Ian1981]

Common misconception this one. Not sure how people think there could be such a maximum figure when the length of run could be absolutely anything.

Problem is that it’s taught in college that 0.05 is the maximum it can be and that any reading higher,a larger csa of conductor needs to be installed. My apprentice picked up on it because I’d warned him about it and the lecturer did not like being challenged on it.

 

[Pretty Mouth]

Good evening

I was always taught the gas and water bonds should have a continuity ideally with a maximum of 0.05 ohms, is this a exact maximum or a rule of thumb and if it was higher than this what coding would we give it? I had a look through the codebreakers booklet but could not bit see an answer

Cheers
HARRY

I was incorrectly taught this too, and it's even in one of Chris Kitcher's books (see my post here: Gas bonding - https://www.electriciansforums.net/threads/gas-bonding.181362/page-2#post-1594732)

But the above comments are correct, there is no required maximum resistance.

 

[happysteve]

Table I1 of the OSG suggests 1.83mΩ/m for 10mm, 3.08mΩ/m for 6mm. Guestimate the rough length of the bonding run, multiply the two numbers (length x 1.83, say), divide by 1000, maybe allow a maximum 0.05Ω for the clamp to pipe resistance... if wildly different, start investigating/checking your working/checking your nulling etc, and if still wildly different, start coding.

There will often be parallel paths (e.g. if there's a gas boiler) so the resistance may be significantly lower than the theory. But the calculations will put a rough maximum on it.

 

[newfutile]

i believe the 0.05 ohm is stated in GN8 , tho my copies at work right now

 

[Ian1981]

i believe the 0.05 ohm is stated in GN8 , tho my copies at work right now

No It’s not because there’s no such figure for a maximum resistance of a bonding conductor

 

[telectrix]

No It’s not

it's not in GN3, or his book's not at work?
[automerge]1585638819[/automerge]
post #2 by dave gives a detailed correct view of this.

 

[Ian1981]

it's not in GN3, or his book's not at work?
[automerge]1585638819[/automerge]
post #2 by dave gives a detailed correct view of this.

A clear explanation is given in guidance note 3 as to where the 0.05 figure comes from.
Dave’s is spot on.

 

[davesparks]

i believe the 0.05 ohm is stated in GN8 , tho my copies at work right now

Many numbers are stated in GN3 relating to all sorts of things, but none of them are given as the maximum resistance of a bonding conductor.

 

[newfutile]

not GN3 but GN8 earthing and bonding

 

[davesparks]

not GN3 but GN8 earthing and bonding

Yes, my mistake, but my point still stands. There is no specified resistance for bonding conductors.

GN8 suggests 0.05 ohms as the upper limit for the resistance between the earth clamp and the pipe to prove that it is in good electrical contact.

 

[Ian1981]

I have gn3 updated to the 18th edition.
I have gn8 which is the 17th edition amendment 3 version.
The 0.05 is mentioned in gn3 not gn8 unless this has changed in the updated version?