Just read a PIR and it states that there is no means of earthing (TT supply with no earth rod). But it also says that the External Loop Impedance is measured at 648ohms. How did they measure that with no supplied earth?
Question about ELI
- Thread starter Podooser
- Start date
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Maybe off the incomming water, gas or oil supply? (Which acts as an earth rod)
None of these are allowed to supply the property with an earth.
None of these are allowed to supply the property with an earth.
They should have recorded it as a Zdb, not a Ze.......but this is a little anal.
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We see many old school TT's here, most still with the obsolete Voltage Operated ELCB's.......with an earth conductor going to an unknown destination......or to the front door......where it is chopped!
Lectrician said:
Why??
As it aint a Ze - The Ze is external, and if there is no rod.....there is no external
Lectrician said:As it aint a Ze - The Ze is external, and if there is no rod.....there is no external
I disagree - if there is a 'reading' of 648 ohms then there must be a path to the Tx somewhere (albeit high) and as the Tx is external then this is the external loop impedance ie Ze......
Nope. Don't agree.
Yes, there is an external impedance of some sort. But it was not designed for the DB, it is in effect most likely 'back feeding'.
I am going by what we are instructed to put on a Periodic Report of an installation with no true earth electrode by the NIC. (yes, they don't make the rules, but this one makes plenty of sence to me).
The Ze is formed by the MAIN EARTHING CONDUCTOR back the MAIN EARTHING TERMINAL and then finds a sweet route back to the sub.
Yes, there is an external impedance of some sort. But it was not designed for the DB, it is in effect most likely 'back feeding'.
I am going by what we are instructed to put on a Periodic Report of an installation with no true earth electrode by the NIC. (yes, they don't make the rules, but this one makes plenty of sence to me).
The Ze is formed by the MAIN EARTHING CONDUCTOR back the MAIN EARTHING TERMINAL and then finds a sweet route back to the sub.
Zdb = Earth loop impedence at the dist board.
Ze = External earth loop impedence.
Ze = External earth loop impedence.
Good job I don't take much notice of NIC guidelines then - ah well.........................
With an earth loop tester at the DB
Ah riccle - It may be an NIC guideline, but it is also an obvious and staright forward assesment.
You cannot have an external loop impedance if one has not been DELIBERATELY constructed.
You cannot have an external loop impedance if one has not been DELIBERATELY constructed.
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