earthing conductor query

**uksel** · 09-02-2010

here's the question

scenario: a TN-S system, where the main earthing terminal is external to the distribution board.

the cable connected to the suppliers earth and the main earthing terminal is the main earthing conductor.

what is the title given to the protective conductor connecting the main earthing terminal to the distribution board (this is also the earth fault path for each cpc)

is it a main bonding conductor, or would it still be classed as the main earthing conductor?

your thoughts are appreciated...

**acat** · 09-02-2010

Originally Posted by uksel

here's the question

scenario: a TN-S system, where the main earthing terminal is external to the distribution board.

the cable connected to the suppliers earth and the main earthing terminal is the main earthing conductor.

what is the title given to the protective conductor connecting the main earthing terminal to the distribution board (this is also the earth fault path for each cpc)

is it a main bonding conductor, or would it still be classed as the main earthing conductor?

your thoughts are appreciated...

IMO the cable would be the main earthing conductor as the cable I take it is continious to MET new cable to distribution board would be bonding.

Interesting question be interested in other peoples views

Chris

**JulianC** · 09-02-2010

I usually refer to this as the main earthing conductor, as well as the bit the other side of the MET, although the definition in the BRB states that this is between earth and the MET only. Given the apparent absence of a defined name for this bit of cable and given what it does I hearby christen it the main CPC.

**uksel** · 09-02-2010

Originally Posted by JulianC

Given the apparent absence of a defined name for this bit of cable and given what it does I hearby christen it the main CPC.

LOL - I'll make city and guilds aware of the revelation

as defined, main bonding conductors are used to connect extraneous conductive parts, not exposed conductive parts, so that should rule that option out

and the main earthing conductor is clearly defined as the connection from the suppliers means of earthing to the MET

here's a surprising one

definition:

Circuit protective conductors (CPC’s)
A protective conductor connecting exposed-conductive-parts of equipment to the main earthing terminal

I would say that's fairly definitive - a susprising answer but definitive

**Jason.S** · 09-02-2010

I would go with MEC from Earth point to CU via MET.

If there was no MET installed then it would be no different.

**Notsosmart** · 09-02-2010

According to BRB figure 2.1 (Page32) it should be called "earthing conductor"

**uksel** · 09-02-2010

that's a drawing of a TT system mate

**Notsosmart** · 09-02-2010

Originally Posted by uksel

that's a drawing of a TT system mate

Not so; look again it is actually termed " Illustration of earthing & protective conductor terms" & look carefully you will see E is "other means of earthing (TN systems)"

**uksel** · 09-02-2010

right you are, so with 'B' being the main earthing terminal (external to the db), doesn't show connection to a CU or DB

if it's connecting to the exposed conductive part of the CU i.e. mettalic covering, then it's bonding.

but i'm asking specifically what the conductor that connects the MET to the earth bar in a DB.

purely on definition i'd say CPC
on practicality and it's function i'd say main earthing conductor