Main Protective Bonding Conductor

[dave992]

Hi, testing a UNI with one main supply, which in turn feeds around 10 separate building. Each building as it own Gas supply with meter, so therefore a Protective Bonding Conductor to each incoming supply. Does the size of the cable have to correspond to the incoming supply size, or to the size of the cable taken into the building. Also do all the bonds have to be taken back to your main earthing terminal , so right back to your main electrical intake point?

Hopefully ive made it sort of clear but im sure if i havnt your ask me something

Thanks

 

[telectrix]

i'd bond each gas supply to the earthing terminal (EMT) in each building. what's the earthing arrangement?

 

[Engineer54]

Main bonding of ALL incoming metallic pipework/metalwork is required at each separate building whether the service has a meter or not. It is to be connected to the buildings MET, or as in this case it will be EMT's....

I'll await the answer to Tel's question about the supplies earthing arrangement to comment further...

 

[dave992]

thanks for that, sorry about delay in answering your question. the earthing arrangement is a TN-S.

 

[cliffed]

Hi, testing a UNI with one main supply, which in turn feeds around 10 separate building. Each building as it own Gas supply with meter, so therefore a Protective Bonding Conductor to each incoming supply. Does the size of the cable have to correspond to the incoming supply size, or to the size of the cable taken into the building. Also do all the bonds have to be taken back to your main earthing terminal , so right back to your main electrical intake point?

Hopefully ive made it sort of clear but im sure if i havnt your ask me something

Thanks

a good question ,I would say it corresponds to the incoming supply,& not the size of supply cable,ie sub main.But very rarely seen.

 

[Knobhead]

For the circuits in each separate building where do the CPC’s go? Now think where the gas bonding should go.

 

[jamie-spark]

Hi, testing a UNI with one main supply, which in turn feeds around 10 separate building. Each building as it own Gas supply with meter, so therefore a Protective Bonding Conductor to each incoming supply. Does the size of the cable have to correspond to the incoming supply size, or to the size of the cable taken into the building. Also do all the bonds have to be taken back to your main earthing terminal , so right back to your main electrical intake point?

Hopefully ive made it sort of clear but im sure if i havnt your ask me something

Thanks

The size of the bonding conductors to each building is sized on the origin of the installation ie the mains position. You can often find the bonding conductors to the various buildings are larger than there supply conductors.

Example
Supply to out building 4core 25mm swa. And where it's pme u may require a 50mm copper csa cable,for the bonds

 

[Engineer54]

Let's put it this way, depending on what size 4 core cable is being supplied to each of these 10 buildings, i hope you're not using the SWA as a combined CPC and main bonding conductor. It's fine to use the armouring as the circuits CPC, but not when it forms any part of a main bonding system... It's then either a 5 core cable, or run in a suitably sized separate green/yellow bonding conductor....

 

[dave992]

Let's put it this way, depending on what size 4 core cable is being supplied to each of these 10 buildings, i hope you're not using the SWA as a combined CPC and main bonding conductor. It's fine to use the armouring as the circuits CPC, but not when it forms any part of a main bonding system... It's then either a 5 core cable, or run in a suitably sized separate green/yellow bonding conductor....

Hi, thanks for the response. With guard the SWA as CPC and main protective bonding conductor, i believe that a separate CPC was taken to each building. Going back to the SWA as your main protective bonding conductor, i know your not allowed to used it for that but what regulation would you use? Thanks

 

[Richard Burns]

Hi, thanks for the response. With guard the SWA as CPC and main protective bonding conductor, i believe that a separate CPC was taken to each building. Going back to the SWA as your main protective bonding conductor, i know your not allowed to used it for that but what regulation would you use? Thanks

544.1.1
Remembering that the equivalent conductance of steel is 8.5 times less than that of copper and so requires 8.5 times the tabulated csa.

 

[dave992]

aww ok so needs to be 8.5 x bigger than a copper cable. Thanks