supply types

[paul b b]

Ok chaps, i think it mabe a good idea for all of the new people on here ,cough cough, to explane the difference between TN-C and PME etc.

im sure they will be most greatful.

oh, it will best also if you explane to if the coverd thing that goes from the supply cabel on a overhead, to the ground under a cover is an earth.

thanks (from the others)

 

[revjames]

TNC-S is a combined neutral/ earth conductor, usually linked at the N and E terminals of the supply (used to be called PME protective multiple earth). TN-S is a separate N and E conductor. TT provides no incoming earth and the consumer provides his/her own earth electrode which is connected to their own earth terminal in their installation.

 

[paul b b]

so PME is TNC-S

 

[revjames]

In essence yes but do get used to calling it TNC-S as correct terminology is important esp in exams. Not sure what you mean by 'covered thingy'.....

 

[Evans Electric]

.... " covered thingy" .... is a technical term that all of us highly knowlegable sparkies use all the time , it means..... Oh ... Erm.... me dinners ready.. must go. !!

Deke

 

[Apache]

Is this helpful?

http://www.theiet.org/publishing/wiring-regulations/mag/2005/16-earthing-questions.cfm?type=pdf

 

[user 6351]

The thing that always bothers me is when the earth is connected into the same suppliers equipment as the line and neutral come out of (sorry, probably a lousy explanation, but I think you'll all know what I mean!!!) it can/could be hard to tell the supply characteristics... If the supply is TN-C-S, is this always clearly marked by the supplier, and do we therefore assume that the earth is connected to the sheath inside the supply equipment (and therefore TN-S)?

 

[revjames]

If its overhead and theres only 2 wires you can assume its TNC-S likewise if its a paper lead incomer its very likely to be TNS if theres an earth rod and an RCD on the incomer then its going to be TT. I am not sure how easy it would be to phone the supplier if you werent sure. I did a PIR last week on an industrial unit and had to take the cover off the cutout (but not the fuses themselves) to reveal the neutral was linked. Yes they should mark it.

 

[Bez]

The thing that always bothers me is when the earth is connected into the same suppliers equipment as the line and neutral come out of (sorry, probably a lousy explanation, but I think you'll all know what I mean!!!) it can/could be hard to tell the supply characteristics... If the supply is TN-C-S, is this always clearly marked by the supplier, and do we therefore assume that the earth is connected to the sheath inside the supply equipment (and therefore TN-S)?

TNCS (PME) You should be able to see the earth wire exiting the neutral block along with the neutral tail. There is normally a warning sticker warning of PME.

 

[Bez]

Oh, I see your point now, if the whole gubbins is hidden

 

[Andy™]

The thing that always bothers me is when the earth is connected into the same suppliers equipment as the line and neutral come out of (sorry, probably a lousy explanation, but I think you'll all know what I mean!!!) it can/could be hard to tell the supply characteristics... If the supply is TN-C-S, is this always clearly marked by the supplier, and do we therefore assume that the earth is connected to the sheath inside the supply equipment (and therefore TN-S)?

it can he hard to tell on some service heads. a loop reading on L-E & L-N will usually tell if its TNCS or TNS. PME usually has a sticker on