I realise this overlaps with the Earth Rod install post a little, but I am attempting to plan part one of an upgrade. Currently I am mostly confident I have TNCS supply (there is a query with the DNO to confirm) but I am a little confused by the additional strap to the lead sheaf in a TNS kind of way.
Currently, there is a gas meter about an inch away from the old fuse box, that is supplied by a plastic main, and a lead water main. Neither of these are bonded. There is a 6mm earth cable from the existing fuse box to the DNO earth point. The fuse board has a 40A cooker circuit, a single 32A breaker for the entire 4 bed house and a single 5A breaker for all the lighting.
The meter was recently replaced, and the chap put an isolator switch in for me.
The long term plan is to replace it all, but I am splitting into 2 building regs applications.
The first will put in a consumer unit with a 63a 30ma RCD protecting a supply to some outside sockets 32a B, outside lighting on a 6a B, a hot tub supply on a 32a C, and a 32a B radial circuit to supply a laundry room. There will also be a 80a fused switch off a Henley block supplying a 37m run to a garden office. This will have a smaller consumer unit in with a 80a 30ma RCD and 40a B for a 10kw instantaneous water heater, a 32a B for sockets in the office and workshop, a 6a B lighting circuit, and 20a D for a 16a 2PE commando for a welder.
Part of the work will also replace the lead water main with MDPE. My question relates to the earthing and the possibility of PEN failure. I had first considered bonding the new system to the gas and water, but reading around it, there seems to be the suggestion that with plastic supplies on both, it is not necessary, and may introduce risk. Also, the braid from the earth point to the lead sheaf. It looks like ancient aluminium braid, or could be tinned copper, either way, I am genuinely concerned that it may burst into flames if asked to carry any level of current.
With the talk of PEN fault taking an alternative path to earth, I am left considering whether it should have a 16mm bond added, or whether the braid should be removed.
I dare not ask the question about adding an earth rod to the TNCS system. I cannot find a copy of the apocryphal document by Paul Cook of the IEE on the benefits of adding a stake to TNCS. I have seen some discussion that adding a stake to TNCS is effectively the same as PME, but also the counters of it being the neutral for all your neighbours and the stake not having a good enough earth to realistically reduce touch voltages below 50v in a PEN failure. It appears that most installs of a hot tub within reach of a house use the available earth rather than TT, because it is better.
The rest of the ring mains would be replaced over winter. The plan is to use the garden office and hot tub during summer, then power off and isolate the new install, submit another application for the house ring mains, and do those over winter by installing new sockets and switches, in parallel, to the old ring mains and lighting, then once inspected and if passed, rip out the old and plaster up the holes.
I am understanding that the old stuff doesn’t have to be brought up to regs if not touched. Would the addition of a Henley block in its supply and upgrading the earth to 16mm change that, or can it remain as is?
Currently, there is a gas meter about an inch away from the old fuse box, that is supplied by a plastic main, and a lead water main. Neither of these are bonded. There is a 6mm earth cable from the existing fuse box to the DNO earth point. The fuse board has a 40A cooker circuit, a single 32A breaker for the entire 4 bed house and a single 5A breaker for all the lighting.
The meter was recently replaced, and the chap put an isolator switch in for me.
The long term plan is to replace it all, but I am splitting into 2 building regs applications.
The first will put in a consumer unit with a 63a 30ma RCD protecting a supply to some outside sockets 32a B, outside lighting on a 6a B, a hot tub supply on a 32a C, and a 32a B radial circuit to supply a laundry room. There will also be a 80a fused switch off a Henley block supplying a 37m run to a garden office. This will have a smaller consumer unit in with a 80a 30ma RCD and 40a B for a 10kw instantaneous water heater, a 32a B for sockets in the office and workshop, a 6a B lighting circuit, and 20a D for a 16a 2PE commando for a welder.
Part of the work will also replace the lead water main with MDPE. My question relates to the earthing and the possibility of PEN failure. I had first considered bonding the new system to the gas and water, but reading around it, there seems to be the suggestion that with plastic supplies on both, it is not necessary, and may introduce risk. Also, the braid from the earth point to the lead sheaf. It looks like ancient aluminium braid, or could be tinned copper, either way, I am genuinely concerned that it may burst into flames if asked to carry any level of current.
With the talk of PEN fault taking an alternative path to earth, I am left considering whether it should have a 16mm bond added, or whether the braid should be removed.
I dare not ask the question about adding an earth rod to the TNCS system. I cannot find a copy of the apocryphal document by Paul Cook of the IEE on the benefits of adding a stake to TNCS. I have seen some discussion that adding a stake to TNCS is effectively the same as PME, but also the counters of it being the neutral for all your neighbours and the stake not having a good enough earth to realistically reduce touch voltages below 50v in a PEN failure. It appears that most installs of a hot tub within reach of a house use the available earth rather than TT, because it is better.
The rest of the ring mains would be replaced over winter. The plan is to use the garden office and hot tub during summer, then power off and isolate the new install, submit another application for the house ring mains, and do those over winter by installing new sockets and switches, in parallel, to the old ring mains and lighting, then once inspected and if passed, rip out the old and plaster up the holes.
I am understanding that the old stuff doesn’t have to be brought up to regs if not touched. Would the addition of a Henley block in its supply and upgrading the earth to 16mm change that, or can it remain as is?
