Supplementary bonding?

[odawire]

Met someone the other day, he told me he was a lecturer teaching electrical installation at the local collage, he said that if you have main water and gas bonded you don't need any supplementary bonding regardless of whether you have RCD protection or not. I didn't want to argue with him too much as he is a teacher but I was pretty sure that it only applies if all circuits are RCD protected? Is this some new rule I've missed?

 

[Engineer54]

Which pretty much shows the level of college lecturers these days!! Supplementary bonding is what say's, ''Supplementary''.

Meaning supplementary to the main earth bonding conductors!! I take it you're referring to bathroom requirements here?? Personally i cross bond bathroom pipework whether RCD protected or otherwise!!

 

[stigwart]

Which pretty much shows the level of college lecturers these days!! Supplementary bonding is what say's, ''Supplementary''.

Meaning supplementary to the main earth bonding conductors!! I take it you're referring to bathroom requirements here?? Personally i cross bond bathroom pipework whether RCD protected or otherwise!!

Yeah agreed, although I wouldn't want to rely on it, but if you measure no more than 0.05 ohms between c.p.c's and extraneous conductive parts in bathrooms, supplementary bonding would not be required.

 

[telectrix]

the problem is that nowadays most pipework in bathrooms is supplied via east-fit plastic so a 5 day wonder wet-pants can do it, so therefore is not extraneous. this is where you need to IR test to MET and if it's not extraneous, don't bond it.

 

[shagbite]

grammar.

 

[Guitarist]

He is wrong! Maybe he ought to get himself a copy of GN8.

 

[i=p/u]

Is it not > 21kohms

 

[Geoffsd]

Yeah agreed, although I wouldn't want to rely on it, but if you measure no more than 0.05 ohms between c.p.c's and extraneous conductive parts in bathrooms, supplementary bonding would not be required.

That is/would be true but 0.05Ω is not the relevant value.

 

[stigwart]

0.05 is the magic number, your equipotential bonding cannot exceed this in ohms, R1 + R2 on your ring final continuity ring tests have to be within this value also.

I think the value your thinking of is 1667 ohms from the equation:
50v/0.03A= 1667 ohms but this figure is deemed unstable.

 

[i=p/u]

Cuckoo .....

 

[stigwart]

Cuckoo .....

What is? Simple ohms law mate...

 

[DJ Ovengloves]

Jesus Christ, where do I start?

You are confusing equipotential bonding with supplementary bonding...that's bad enough. But the R1 + R2 for a RFC comment just beggars belief!

Give up before you kill someone!

0.05 is the magic number, your equipotential bonding cannot exceed this in ohms, R1 + R2 on your ring final continuity ring tests have to be within this value also.

I think the value your thinking of is 1667 ohms from the equation:
50v/0.03A= 1667 ohms but this figure is deemed unstable.

 

[Kamikaze]

What is? Simple ohms law mate...

Let’s put it this way. Lets assume you are on a TN-CS system with a Ze of 0.35 Ohms at the board. If your theory that the sum of R1 & R2 on a ring must not be grater than 0.05 ohms. You would have to condemn your ring circuit with a Zs greater than 0.40 ohms. Can you see what’s wrong with your theory?

 

[Marvo]

I was confused before I read this thread but I'm even worse now. Maybe this will help.

 

[stigwart]

I didn't explain myself very well, all the readings on a true ring should be the same within 0.05 ohms so for example 0.45 on one 0.50 on another.