Testing Zs - disconnect main bonding or not ?

[rick]

Hi

When measuring Zs on circuits do you guys leave the main bonding connected or disconnect it? Most of my testing books including GN3 say leave it connected, but another book by Anthony Hinsley says to disconnect it as it will introduce parallel paths (which I get) and that if left connected there is a risk of shock induced into other electrical systems in close proximity (which I don't...)

So what's the verdict?

Cheers

 

[Spudnik]

Yes you MUST reconnect bonding to carry out Zs testing.

GN3.

 

[Guest123]

Main bonding connected for Zs testing......normal service conditions.

 

[Eggster71]

Only ever disconnect bonding for Ze

 

[rick]

Thanks guys - looks like the Hinsley book isn't the one to trust !

 

[Risteard]

Perhaps it's referring to EXTERNAL Earth fault loop impedance (Ze)?

 

[lamb]

The main switch must never be switched ON with main bonding disconnected.

Therefore you could not possibly measure Zs with bonding disconnected.

Furthermore, the preferred method during initial verification and PIR testing is to carry out all dead tests and Ze measurement with the main switch locked off. Afterwords the Zs for each final circuit can be calculated using Ze+R1+R2. This is safer because it reduces the amount of live testing.