Having had to call the board out recently - flickering supply and overheating main fuse - I was impressed by how efficiently everything was repaired. I know I wouldn't have fancied the hot working.
What I hadn't been aware of was that we were on PME, and now the new fuse has a label to that effect. As it happens, the recent work I did included upgrading the earth bonding, and was easily sufficient for PME, but should the type of earth have been apparent to me?
Chris
"Chris J Dixon" wrote | Having had to call the board out recently - flickering | supply and overheating main fuse - I was impressed by | how efficiently everything was repaired. I know I | wouldn't have fancied the hot working. | What I hadn't been aware of was that we were on PME, | and now the new fuse has a label to that effect. As | it happens, the recent work I did included upgrading | the earth bonding, and was easily sufficient for PME, | but should the type of earth have been apparent to me?
It's possible that you weren't on PME before, and when replacing the main fuse assembly they took the opportunity to 'upgrade' you.
You should have known what your earthing was before, because it affects cable calculations and protection methods, and is a fundamental part of completing a test and isnpection certificate.
Owain
No, the cable was not changed, and had only live & neutral. What I meant was, ought the type of earthing to have been apparent to anybody working on the system, in the absence of any labeling.
I understand that it is necessary to know, for the reasons you state, but there was no visible indication or other documentation.
Chris
understand that it is necessary to know, for the reasons you
I am on PME earthing and on the right hand side of the incomer fuse is an earthing block with the earth cable going to my consumer unit. This is in a Seeboard area, maybe yours is different in Notts.
Trevor Smith
Christian.
I'm sure I should know - but what is PME ?
It is good policy to assume that, even what may be a standard acronym to the author, is not known by the reader and should always be spelled out once fully in a document.
Rob
Maybe in an academic manuscript or something, but this here is the land of Usenet where we have the benefit of FAQs, which exist for the purpose of not having to explain everything every time (amongst other reasons)
Try
It stands for Protective Multiple Earth and is an obsolete term for describing what is now known as TN-C-S. These letters, which are based on French indicate that:
T - earth is related to ground potential. (alternative being I- isolated) N - earth is provided by the supplier C - the supplier's installation combines the earth and neutral into a single conductor. S - the user's installation has the earth and neutral in separate conductors.
The other commonly used systems are: TT - earth is provided by a local earth rod. (Should probably be called TT-S, but isn't).
TN-S - earth is provided by the supplier using their own specific earthing conductor, not sharing with neutral.
Other systems are possible, but are not usually legally permitted on fixed installations.
Unfortunately, in a technical discussion, it is not possible to avoid the use of jargon and acronyms without disrupting the argument. Many online resources are available for those wishing to get up to speed.
Christian.
I wouldn't say it was obsolete. From the consumer's point of view, on a public mains supply, "PME" and "TN-C-S" are synonymous. But if you think about it more generally, nothing in "TN-C-S" /per se/ implies multiple earthing. So the supply distributor builds a PME network in order to give the consumers TN-C-S supplies, IYSWIM.
Silly question - is this 'ground', as in the big ball of stuff we're all sitting on?
More or less. UK = Earth, USA = Ground, don't know what the frog-eaters et. al. call it!! :-) It should be at zero potential in relation to all live conductors, and is normally? bonded to neutral at the generator and sub-stations.
I thought that's what foot-notes where for, quoting and citing such resources etc. ?...
Ok. I thought this was the case, but was wondering if there was some strange non-obvious definition. ... Idly wonders what the resistance from the UK to USA is.
They call it "terre", hence the 'T'.
Christian.
Aye, but, every 'good' news group worth it's salt has a FAQ, and whenever a reader, lurker or poster comes across something which he/she doesn't understand, then he/she is supposed to read the FAQ first, and only post a query if it's not in the FAQ. ;-)
BTW, FAQ = Frquently Asked Questions.
BTW, BTW = By the way.
Yes, assuming they know what the FAQ's URL is, otherwise perhaps they should post a FAQ to ask were to find the FAQ's so that they don't need to ask a FAQ ?....
Blindingly obvious, or what? Will think first next time...
Apparently very much less than proportionate to the resistance from your house to the substation. The distance is huge but so is the cross-sectional area. AIUI the bulk of the resistance to ground is near the earth rods where pathways for the current are bunched together.
No they should just do:
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