Should electricians assume TN-S and TN-C-S are both PME earthing systems.
When electricians are working on a TNS earthing system should they consider that it may change to TNCS in the future? This could happen when the DNO, distribution network operator, repairs or upgrades the electricity supply around the installation area.
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Presented by
Gary Parker - Technical manager - Electrical Contractors Association. (ECA)
Joe Robinson - Technical editor eFIXX
#efixx #morepower #electriciansQ&A
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!!
Clear as mud that Gary....I will stick to using my own common sense
Common sense is the best way:-)
Yeah, clear as mud 😂😂
Me: Does this property have a TN-S or TN-C-S earth system? DNO: Yes.
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
hi im new to this what what is the bsen number for a switch fuse isolater at 125amp its 4 pole regards jas
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).
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
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!
There is no way the DNO can guarantee they haven't repaired a TN-S and therefore you must assume TN-C-S.
The truth is the DNO Don't really know what systems they supply either. 😂 Some Teflon shoulders going on... Ass covering.