I am considering the options which may apply to the earthing arrangement for a supply to a wooden shed.
The property has a TN-C-S supply from which a 60A isolator feeds a 3-core 16mm2 swa sub main 13 metres to a detached garage. The property has a supplementary earth rod and the garage also has another supplementary earth rod. In the garage is a 50:50 split fully RCD protected board and an earth marshalling block to connect the cpc's. So the garage is an extension of the property equi-potential zone. I am proposing to take a 16A supply from the garage board to a wooden shed using a 35 metre run of 3-core 6mm2 swa cable which has already been installed underground. My question is primarily whether I should export the earth and extend the equi-potential zone again or opt for a TT system. In either case I propose to install an earth rod adjacent to the shed which if not used as a separate earth would be used as a supplementary earth.
My secondary questions are:
1). If the installation can be done as pme, can the c.s.a of the earth conductor and armour be combined to satisfy the 10 mm2 requirement for a bonding conductor?
2). Although earth leakage discrimination is not vital could this be achieved on a pme installation or is this a good reason to go for TT?
3). Do I have a choice? I have a preference for extending the equi-potential zone with multiple earth rods as I think this gives better protection when using power tools on leads which can reach from one building to another.
I am not an electrician which is why I am raising these questions. I will be completing the electrical design and installation in accordance with the current edition regulations in readiness for a Part P qualified electrician to inspect and test the work.
The property has a TN-C-S supply from which a 60A isolator feeds a 3-core 16mm2 swa sub main 13 metres to a detached garage. The property has a supplementary earth rod and the garage also has another supplementary earth rod. In the garage is a 50:50 split fully RCD protected board and an earth marshalling block to connect the cpc's. So the garage is an extension of the property equi-potential zone. I am proposing to take a 16A supply from the garage board to a wooden shed using a 35 metre run of 3-core 6mm2 swa cable which has already been installed underground. My question is primarily whether I should export the earth and extend the equi-potential zone again or opt for a TT system. In either case I propose to install an earth rod adjacent to the shed which if not used as a separate earth would be used as a supplementary earth.
My secondary questions are:
1). If the installation can be done as pme, can the c.s.a of the earth conductor and armour be combined to satisfy the 10 mm2 requirement for a bonding conductor?
2). Although earth leakage discrimination is not vital could this be achieved on a pme installation or is this a good reason to go for TT?
3). Do I have a choice? I have a preference for extending the equi-potential zone with multiple earth rods as I think this gives better protection when using power tools on leads which can reach from one building to another.
I am not an electrician which is why I am raising these questions. I will be completing the electrical design and installation in accordance with the current edition regulations in readiness for a Part P qualified electrician to inspect and test the work.