According to the new EVC CoP, TN-S should be assumed to be TN-C-S unless the DNO confirms in writing that it is TN-S and will always remain TN-S - if not, assume it's TN-C-S!!
Western Power advised me in November 2020 that they don't have records for the earthing arrangements in dwellings. They were not keen on arranging a visit to the property in order to investigate. ESQCR rules must have changed since this video was published.
I did ask (as a non-electrician but curious as the on-site arrangement looked a bit like TN-S) but I guess assuming it is TN-C-S is safe and when I did have my EICR (before moving in) the earth loop impedance reading was in TN-C-S bounds. I didn't pursue the matter. I was surprised they didn't actually know though!
@@seprishere Does ''TN-S should be assumed to be TN-C-S'' mean the lead sheathing of the cable that comes into the house is joined to the neutral of modern TN-C-S type cable in the street somewhere that takes it back to the distribution transformers star point? Because if the lead sheath is not connected to the neutral conductor at some point then the main earth terminal is not earthed as far as I can tell (other than through extraneous conductive parts).
@@Orgakoydit’s only tn-s if the *entire* path to the transformer is separated *and* the DNO plans to never change that. Given that new underground cables are pretty much universally C in the UK, that means that even if it’s currently non-C any repair in the line at any point will change it to Tn-C-S. So as long as that’s true, assuming TN-S is essentially unsafe, at least in residential/small office context. Maybe if you’re a large industrial client with your own transformer, things become more complex than that.
@@JasperJanssen Thank you for that. I’m always keen on learning more about this stuff. I read a western power PDF from 2019 that said they have standardised on a minimum service cable size, and minimum distribution transformer size going forward, so that the distribution grid is able to handle increase in load in the future. Also that all new cables, and any replacement cable going forward will be 3 phase, connected underground in the street and brought into the building ready for a 3 phase supply in the future, and also giving opportunity to swap phases around easily for balancing, whereas currently it’s not possible other than digging up the joint under the street.
I have a PME sticker on my board.... the earth is bonded to the neutral in the garden from an over head cable landing in the ground. The supply is fragile in high winds. Decided to go off grid and install my own earth. Can a locked mechanical transfer switch or isolator be installed on the consumer side or prosumer as I will be when offgrid? If I am off grid completly then I can up the no. of solar panels without restriction by the DNO. Any info on this is welcome. Cheers
According to the new EVC CoP, TN-S should be assumed to be TN-C-S unless the DNO confirms in writing that it is TN-S and will always remain TN-S - if not, assume it's TN-C-S!!
Yeah, clear as mud 😂😂
Clear as mud that Gary....I will stick to using my own common sense
Common sense is the best way:-)
Me: Does this property have a TN-S or TN-C-S earth system?
DNO: Yes.
Western Power advised me in November 2020 that they don't have records for the earthing arrangements in dwellings. They were not keen on arranging a visit to the property in order to investigate.
ESQCR rules must have changed since this video was published.
I did ask (as a non-electrician but curious as the on-site arrangement looked a bit like TN-S) but I guess assuming it is TN-C-S is safe and when I did have my EICR (before moving in) the earth loop impedance reading was in TN-C-S bounds. I didn't pursue the matter. I was surprised they didn't actually know though!
@@seprishere Does ''TN-S should be assumed to be TN-C-S'' mean the lead sheathing of the cable that comes into the house is joined to the neutral of modern TN-C-S type cable in the street somewhere that takes it back to the distribution transformers star point? Because if the lead sheath is not connected to the neutral conductor at some point then the main earth terminal is not earthed as far as I can tell (other than through extraneous conductive parts).
@@Orgakoydit’s only tn-s if the *entire* path to the transformer is separated *and* the DNO plans to never change that. Given that new underground cables are pretty much universally C in the UK, that means that even if it’s currently non-C any repair in the line at any point will change it to Tn-C-S. So as long as that’s true, assuming TN-S is essentially unsafe, at least in residential/small office context. Maybe if you’re a large industrial client with your own transformer, things become more complex than that.
@@JasperJanssen Thank you for that. I’m always keen on learning more about this stuff. I read a western power PDF from 2019 that said they have standardised on a minimum service cable size, and minimum distribution transformer size going forward, so that the distribution grid is able to handle increase in load in the future. Also that all new cables, and any replacement cable going forward will be 3 phase, connected underground in the street and brought into the building ready for a 3 phase supply in the future, and also giving opportunity to swap phases around easily for balancing, whereas currently it’s not possible other than digging up the joint under the street.
Hi so if a swa circuit is fed from the consumer unit on a TN-C-S earthing system does the remote end of the swa change to a TN-S system
No, the earthing arrangement is defined by the means of earthing to the origin of the installation not a sub-main. Good question though.
@@efixx thank you
I have a PME sticker on my board.... the earth is bonded to the neutral in the garden from an over head cable landing in the ground. The supply is fragile in high winds. Decided to go off grid and install my own earth. Can a locked mechanical transfer switch or isolator be installed on the consumer side or prosumer as I will be when offgrid? If I am off grid completly then I can up the no. of solar panels without restriction by the DNO. Any info on this is welcome. Cheers
There is no way the DNO can guarantee they haven't repaired a TN-S and therefore you must assume TN-C-S.
How can you test to confirm it’s TNC-S or TN-S?
Quick question folks
Do we need to earth bond metal beam in a new extension and another one on loft conversion ? Same property.
@@sparkymacsparkface7497they are atm but they will be buried with plasterboard anyway
No unfortunately it doesn't have
Thank you sincerely for your advice
I will give them a ring to make sure its correct
👍
If in doubt
Bond it out!
hi im new to this what what is the bsen number for a switch fuse isolater at 125amp its 4 pole regards jas
The truth is the DNO Don't really know what systems they supply either. 😂 Some Teflon shoulders going on... Ass covering.