Zs (Zbd) at a distribution board

[studentspark]

Getting conflicting advice.

Disconnect supply earth or not (at the distribution board not at the origin)
What about any bonding?

Thanks[/list]

 

[RF Lighting]

You must not have any supplies in the building energised with the main earth or bonding disconnected. This includes submains.

Ze is the suppliers earth in isolation. Zdb is not.

 

[studentspark]

Thanks

I thought so but some notes for the 2391 (2394/5) say disconnect.!!
As do a few forums posters.

Just to clarify.

Main earth is connected, and circuits energised.

Distribution board fed from main board is powered but isolated
I.e main switch at 2nd distribution board is off., but supply terminals to main switch energised.

 

[Lectrician]

Ze is at the origin, with main earth disconnected and main switch off.

Testing an earth loop at a submained DB is a Zs test, but known as Zdb.
Testing Zdb at a submained DB leaves earths in place, as with any Zs test.

If for operational reasons you cannot isolate a supply and disconnect the main earth to carry outs true Ze, you record it as a Zdb.