High earth impedance

[Deleted member 9648]

i am in college just working through earth impedence. Aside from a meter to tell you what the ZE is, is there a forumlar for working it out...thanks

No , but in the case of TNCS ans TNS systems you can make an enquiry to the DNO who should be able to tell you the expected Ze.

 

[Sintra]

You could use the old obsolete water pipe as your earth connection if it exists
It does not have to be a rod 542.2.1

Earth Electrodes

All of the following can be used as earth electrodes :

Earth rods or pipes

Earth tapes or wires

Earth plates

Underground structural metalwork embedded in foundations

Welded metal reinforcement of concrete embedded in the Earth (excluding pre stressed concrete)

Lead sheaths & metal cable coverings provided the following conditions are met :
a - the cable covering must be in effective contact with Earth
b - the permission of the cable owner must be obtained
c - the owner of the cable must be able to inform the owner of the installation of any changes to the cable which may affect it suitability as an earth electrode 542.2.1, 542.2.5,

A metal gas or water pipe must not be used as an earth electrode. 542.2.4

 

[Spudnik]

Can someone pass me my regs book.

Its at the end of my table and ill have to get up.

Ta.

 

[Spudnik]

c - the owner of the cable must be able to inform the owner of the installation of any changes to the cable which may affect it suitability as an earth electrode 542.2.1, 542.2.5,

Like that will happen!

 

[netblindpaul]

Why are BG insisting on earthing connections better than that required in the regs?

 

[Des 56]

The earth electrode cant be a service pipe

It can be a pipe in the ground, for the main earth, where the ground may be too hard, for instance, to sink a rod

So as long as the pipe is an obsolete service pipe and under your control, and its not going to be removed by the water company
I would say that it may provide an approved means of earthing for the TT install
Not that I would recomend this in normal circumstances mind you