Which connector block do I use on a Greenstar boiler when wiring a Wave smart internet connected controller?

Depending on the boiler model, it will either be the BB connection or the EMS connection.

On the Greenstar CDi/Si Compact and the new Greenstar i model the connector block is marked as EMS.

The Greenstar CDI Classic range, discontinued Greenstar i Junior mk5, Greenstar Si mk4, the connector block is the BB connection on ST19.