What is the breaker rating for connecting the 3 voltages to the WEM3080T ?

Would a breaker with 300mA be OK ? I'm assuming the unit is only sensing the voltage on 2 phases and then using some current from the third to actually power itself. At the nominal 2W this is going to be a few mA.

I'm looking at this one
https://nz.rs-online.com/web/p/mcbs/2120123

Hi:

It is enough.
In fact, the breaker is optional, if you do not have a breaker there, you do not need to install a breaker for the WEM3080T

Thanks

Although I would not want anything connected directly to the mains circuit without a breaker. I will make sure a suitable one is installed.