Protective Conductors Continuity

[IQ Electrical]

Can anyone give me a few examples of what parallel earths might be there? Thanks. Got the theory, need the practice ......

Yes, any bonding/supplementary bonding, along with simple cpc connections to items that are bonded by virtue of pipework connections (boilers etc.) right down to luminaires sitting in a conductive ceiling grid.
In all but the most basic 'all-insulated' installations, there are many parallel paths.

 

[Brightspark2]

Yes, the 'back calculation' (R1+R2) = Zs-Ze is distorted by parallel earth paths and should not be used.

Thats the one...


So if people are only testing Zs what do they put in the R1+R2 box on the test sheet? N/A?...

 

[IQ Electrical]

I've seen everything from a tick, N/A, LIM or a back calculated value...

 

[ackbarthestar]

Hi Guys and Dolls
In my 2004 edition of the IEE Inspection and Testing Guidance Note 3, page 78, Protective conductor continuity can be confirmed with an Earth fault loop impedence test (R1 + R2 or R2 is not required to be measured). (Note 4)
Ring circuit continuity also does not have to be measured 'Where there are proper records of previous tests and no changes have been made to the ring final circuit'

Is this still allowable under the latest regime for PIRs?
If so, do you rely on a Zs test only?

Pete :winkiss:

Page 73-74 GN3 5th ed. Cost £25. ------:happy:

 

[pushrod]

Apologies for ressurrecting old thread

Yes, the 'back calculation' (R1+R2) = Zs-Ze is distorted by parallel earth paths and should not be used.

What if doing an inspection (on empty house) and you disconnected main protective bonds and did Zs -would your Zs - Ze = R1+R2?

Seems a lot of hassle when working by yourself to be doing R1+R2 and a Zs at every point when the results don't really show anything new?
(not got access to a GN3 5th ed) Any thoughts?

 

[Brightspark2]

Apologies for ressurrecting old thread


What if doing an inspection (on empty house) and you disconnected main protective bonds and did Zs -would your Zs - Ze = R1+R2?

Seems a lot of hassle when working by yourself to be doing R1+R2 and a Zs at every point when the results don't really show anything new?
(not got access to a GN3 5th ed) Any thoughts?

Test from furthest point on EICR...

 

[Risteard]

What if doing an inspection (on empty house) and you disconnected main protective bonds and did Zs -would your Zs - Ze = R1+R2?

No, because you wouldn't energise the installation with the main protective bonding disconnected.