NECA Technical receive many enquiries in regard to properties with Multiple Earthed Neutrals (MENs).
It is permissible to have more than one MEN, providing the switchboards are in buildings that are separated by land as per the requirements of clause 220.127.116.11 of AS/NZS 3000:2018.
The following figure is an example of a compliant installation with a combination of distribution boards with either a MEN or a running earth.
This installation incorporates a main switchboard and three distribution boards in separate outbuildings.
The main switchboard has a MEN connection at the earth bar and a connection to the main earth electrode. Distribution boards 1 and 2 also have a MEN connection and the earth bars are connected to independent earth electrodes.
There is no MEN connection at distribution board 3, as there is a running earth conductor connected directly to the installation earthing system.
The neutral conductor supplying distribution board 2 cannot rely on a terminal at distribution board 1, and must be continuous to distribution board 2 as required by clause 18.104.22.168 of AS/NZS 3000:2018.