Earth-Neutral Bond

To change the classification of a Sunsynk Inverter from a Class II to a Class I an Earth-Neutral Bond must be created.

Some inverter models have an Earth-Neutral Bond built in whereas other may have hot contacts, dry contacts or a combination of that can be used to create this bond.

Please always refer to your Sunsynk Manual for the connection types of your inverter.

To activate the Earth-Neutral Bond when GRID power is lost Signal Island Mode MUST be selected in the battery settings.

Different makes/manufacturers of contact relays may have different Pin Out configurations. Please refer to the manual of your specific relay before making any connections. The wiring configurations in this guidance are based on the MCG MC2252NO2NC contact relay. This offers the option of two normally open contact relays and 2 normally closed contact relays.

For inverters with Dry Contacts

To create the earth-neutral bond we will need to use a Normally Closed contact relay on the LOAD side. You should use the pins labelled as 'dry contacts' in your relevant manual. The below diagram is a general representation.

When the GRID is active the relay is open. When the GRID is lost the relay closes and creates the Earth-Neutral Bond.

Testing: When Signal Island Mode is enabled and the grid is connected you should be able to measure continuity between the two dry contact ports. When the grid is lost the continuity will also be lost.

For Inverters with Hot Contacts

You should use the pins labelled as 'hot contacts' OR L and N in your relevant manual. The below diagram is a general representation. 

When the GRID is active the relay is open. When the GRID power is lost the relay closes and the Earth-Neutral Bond is created.

When installing in parallel the Earth-Neutral bond relay should only be connected to the Master inverter. This is because in a parallel install all the LOAD terminals should already be paralleled together.

Testing: When Signal Island Mode is enabled and the grid is connected you should measure no voltage between the two hot contact ports. When the grid is lost you should get 230V output.

For further information on Earth-Neutral Bonding please see:

Earth-Neutral Bond (Supplementary Information)