10mm bonding to water and gas

[m1ck_b87]

Adibiatic equation is not used for main bonding conductors

 

[Deleted member 26818]

With installations up to and including 100A, there are very few instances where an earthing conductor with a CSA greater than 10mm² would be required.
Those instances are limited to 100A supplies, with a Ze such that disconnection times would be around the 5 second mark, and would often involve the use of multi core cables.
Even in those instances where a CSA greater than 10mm² is required for the earthing conductor, often 6mm² bonding conductors would be acceptable
As Jay Sparks says, conduct the adiabatic equation to determine what CSA is required for the earthing conductor, then size the bonding conductor accordingly.

 

[m1ck_b87]

Bgb book states minimum size conductor of 10mm in relation to neutral conductor upto 35mm on a tnc-s system. so basically if its a 6mm main earthing conductor the bonding conductor still has to be 10mm, now tn-s is different no less than half rhe size of earthing conductor , so my question to you is would it be acceptable as long as no thermal damage on a tnc-s system.

 

[m1ck_b87]

Would 6mm be acceptable

 

[onions1066]

10mm on a tncs

 

[Deleted member 26818]

Bgb book states minimum size conductor of 10mm in relation to neutral conductor upto 35mm on a tnc-s system. so basically if its a 6mm main earthing conductor the bonding conductor still has to be 10mm, now tn-s is different no less than half rhe size of earthing conductor , so my question to you is would it be acceptable as long as no thermal damage on a tnc-s system.

No, with TN-C-S the minimum CSA of 10mm² applies to both the earthing and bonding conductors.
It is only with TT and TN-S, where the earthing conductor can have a smaller CSA than the bonding conductors.

Yes 6mm² would be considered as acceptable if as you say, there are no indications that the conductors have been overheating.

 

[Midwest]

I'm trying to understand this particular issue. Surley the earthing conductor and main protective conductors are relative to the supply tails, not the size of the cut out fuse (which the DNO could change)?